Home

POLTIPS 3 - National Oceanography Centre

1. m Z Page 37 Note that all times for sunrise and sunset are shown in UTC GMT only If you want to save the sunrise and sunset times in a file select either File Save as Text File click on the save button on the toolbar or press J S while the sunrise sunset table is on screen The data will be saved as a list one line per day which can easily be imported into other software such as Microsoft Word or Excel Page 38 Fixed format tide tables When you compute a high and low water prediction and click on the tide table button you will be presented with the default POLTIPS tide table format This isa 2 month per page format However we have created some additional fixed tide table formats in the software as well as the ability to tailor the layout with a custom tide table see page 43 To bring up one of these formats compute the data as normal then select the appropriate format from the output menu Additional fixed format 1 o New Prediction POLTIPS 3 Fie Edit View Input Output Misc Help alaj amm el Aele ef HIGH WATER AT LIVERPOOL GLADSTONE DOCK Morning H M 08 24 0922 1012 1057 1136 0002 0036 0109 0142 0216 0253 0334 0426 0533 0652 0803 0900 0948 1033 1116 1159 0024 0108 0151 0236 0325 0421 0530 0652 0809 0914 Times are GMT National Oceanography Centre 6 Brownlow Street Liveprool Merseyside L3 SDA JANUARY 2011 Height Metres
2. To incorporate your own harmonic constants into POLTIPS 3 you must modify two files in the POLTIPS directory on your hard disk Unless you changed the default location when you installed POLTIPS this will be c Program Files POLTIPS 3 INDEX DAT Page 51 If you have a customised licence this file will contain a list of the ports already included in POLTIPS 3 however your licence will restrict access to most of them There is an example file called indexusr dat which can replace index dat that contains the additional three example ports included with POLTIPS 3 If you have a UserData licence index dat will contain three sample ports only The index file contains one line per port and includes the short port name three numbers a descriptive piece of text and the long port name optional The spacing of the information on the line is very important see table below Characters Description 1t031 Short port name max 30 characters 32 Port type 1 standard port included by NOC 2 secondary port using time height differences 4 port created with users own constants 33 to 36 Number to indicate how to find the correct data for the port If port type equals 4 this number is the line number in the USERCON DAT file were the data for this port starts 37to 41 If port type equals 1 or 4 this should generally be set to zero If port type equals 2 it is used to indicate the reference port 43 to 122 descrip
3. You can scroll up and down to see the rest of the page using the up and down arrows on the keyboard or the toolbar To move onto the next page of the tide table use the left and right arrows or page up and page down on the keyboard Page 17 To print the tide table select File Print or click the print button on the toolbar From the print dialog you can select which pages of the tide table you wish to print and the number of copies as well has being able to change all the settings specific to your printer Note that on rare occasions it is possible that five tides can occur in one day If this happens POLTIPS will automatically reduce the text size and spacing to fit in the extra tide Why do some days only have three tides The average time between successive turning points is 6 hours and 12 minutes i e four tides take 24 hours and 50 minutes meaning the tide moves on by 50 minutes each day About every 7 or 8 day one of the tides moves across midnight into the next day leaving only three turning points on that day Why is the phase of the moon shown on a tide table The tide is directly related to the phase of the moon Spring tides usually occur 1 to 2 days after new and full moon and neap tides 1 to 2 days after the first and third quarter The moon symbols are shown to enable easy identification of springs and neaps New Moon D First Quarter O Full Moon C Third Quarter Equal Interval Predictions An equal int
4. Page 50 Using your own harmonic constants Users of the standard version of POLTIPS are not licensed to use their own harmonic constants in the program This feature will usually be disabled check the title screen of the program PLEASE READ Do not attempt to use your own harmonic constants in the software unless you e are comfortable editing text files on your PC e arefamiliar with the basic concepts of harmonic prediction About Harmonic Constants The basis of all tidal predictions is a set of harmonic constants for the location of interest With these and the appropriate mathematics for calculating various astronomical parameters it is possible to predict the tide for any date future or past For more information on harmonic constants read the section in the Frequently Asked Questions about Tides page Error Bookmark not defined entitled How can tide tables be produced so accurately If you have your own sets of harmonic constants for a location you can use POLTIPS 3 to compute tidal predictions based on these harmonics for any date and time within your licensed period These harmonics could have been obtained from either a tidal analysis carried out for you by NOC derived from the NOC Tidal Analysis Software Kit TASK or from some other source To use this feature you must have either a POLTIPS 3 customised licence or a POLTIPS 3 UserData licence A UserData licence usually runs for 10 years Data Files
5. 1 3 569 29 1203 56 14 1 ko 061 M 1822 075 W 0641 M 1822 075 W Page 48 Batch Mode Operation Batch mode allows you to compute the tides for many locations and or many different time periods quickly using a file containing details of all the calculations that need to be carried out Before you can run POLTIPS in batch mode you must first set up a POLTIPS Batch File PBF file This is a text file that can be created in any text editor including Windows Notepad which precisely defines all the tidal predictions that you wanttorun Once you ve done this you start the job by selecting Batch Processing Mode from the file menu which will ask you for the PBF file and then start computing the data PBF File Format Each line of the file corresponds to one tide table or text output file The format of a typical line might look something like this ABERDEEN 01 01 2012 31 12 2012 T 60 G 1 MCT 1 XXX FILENAME TXT A 0027 STREF Spacing in this file is critical The different fields mean the following Portname First 31 characters of the line Start date Three integers nn nn nnnn 4 digit year must be used End date Three integers nn nn nnnn 4 digit year must be used Prediction type Single character T turning points E equal interval H high waters only L low waters only Interval Integer value interval spacing in minutes ignored unless prediction type is E however a value must still be entered Daylight saving
6. 1 to 4 months per page of the tide table If you want to use larger font sizes then you may want to select less than the default of 4 months per page 3 pages per year to allow space for the larger fonts Columns per month give you the choice of 1 to 4 columns per month The default and probably the most useful is 2 columns per page Relative positioning allows you to finely adjust ENGLAND WEST bias Sa 5 GMT Lat 51 3 the positioning of the data within its box January February The box is the allocated area on the tide table gt Tm m T 43 n aT an 048 which contains the 4 tides for a particular date 1 ss mene 1 16 one date boxe is shown shaded in the we ezme illustration on the right The size of the box f ae z K en er i can vary depending on the number of columns g we s l ei e 3 p 18 y per month and the number of months per moe i roa am s e i m page therefore the relative positioning values 4 ot 49 oe 20 g o slag w are specified as a percentage rather than an absolute measurement The Date H Time and Height values are the horizontal positioning of the three values It specifies the position of the right hand edge of the numbers as numbers are traditionally right aligned In the illustration that shows the default values the date is right justified 26 of the way across the box the times are 60 across and the heights are 94 across Date V is the vertical positioning of the
7. 7 or 8 day 15 Where can I find out more information about tides There are many books that cover the subject of tides but the reader should be aware of inaccuracies that often exist You should avoid books that talk about the second bulge on the far side of the earth being caused by either the moon s gravity pulling the earth away from the water or by the spin on the Earth on its axis The daily rotation of the Earth on its axis has no effect on tides See page 67 If gravity is always pulling towards the moon what causes the bulge on the opposite side of the earth One excellent book on the subject Tides Surges and Mean Sea Level David T Pugh Published by John Wiley and Sons 1987 ISBN 0 471 91505 X It covers the subject in immense detail but is very mathematical and rather expensive to buy Page 72 Page 73 Glossary Datums see section on Datums on page 20 BST see Time Zones below Diurnal Tides tides that have only one high water and one low water every 24 hours 50 minutes This does not occur in UK waters Ebb Tide the seaward tidal flow from high water to low water The Ebb time is the time between a high water and the following low water Eguinoctial Spring Tides the spring tides that occur closest to the spring equinox and autumn equinox The tidal effect due to the sun is at a maximum since the declination is zero These usually have the largest tidal range of the year i e the h
8. Single character G GMT only B BST adjustment Precision Single digit number 1 2 or 3 decimal places Units Single character M metres F feet Datum Single character C chart datum O ordnance datum S special datum Output format Single character T text file 2 options see subformat C Comma Seperated Values P PDF 2 options see subformat Output subformat Single character used only when format is T or P format T 1 text 2 STFS format P 1 standard 2 use CTT file Page 49 CTT file Custom Tide Table definition file no spaces allowed Used only when output format is P and the subformat is 2 Set this to xxx for other outputs Output file Output Filename no spaces allowed Extra tides What to do when extra tides found A leave all tides in the data R remove any extra tides U user intervention ask at runtime NOC reference 4 digit number used in STFS output format only Station Ref String of characters used as a station reference no spaces allowed 63 characters maximum The STFS format is rarely used now but used to be a popular format for including tidal data into external devices If you have problems using this feature please send an e mail to the applications team applications noc ac uk and attached the PBF file you have been trying to set up If the Output file specifies a subfolder e g output Dover2011 txt the folder must already exist POLTIPS will not create new folders on your hard disk
9. The CD should automatically run the installation program If this does not start after 20 seconds you will need to run the program manually as explained below Click on the start button and select Run In the dialog box type d setup where dis the drive letter of your CD ROM and click OK Follow the on screen instructions POLTIPS 3 will be installed on your computer s hard disk the default location is c Program Files POLTIPS 3 and an icon will be created automatically on the programs menu of your Start Button and on your desktop How to start POLTIPS 3 To start POLTIPS 3 click on the start button select Programs and then POLTIPS 3 Alternatively double click the icon on your desktop Troubleshooting POLTIPS won t compute the tides for the locations or period that you expect When you start POLTIPS your licence details will be displayed on the initial photo screen If this does not match what you expect the licence may not have installed properly Copy the file from the root directory of the POLTIPS CD into the folder in which POLTIPS is installed usually C Program Files POLTIPS 3 Page 11 The Moon Symbols are not appearing on the tide tables The moon symbols font should install when you install POLTIPS however if when viewing a tide table you see the letters A B C and D appearing under the day of the week instead of the moon symbols 5 C the font did not install and
10. are about 150 common harmonic constituents each directly tied in with astronomical influences on the tide Highest and Lowest Astronomical Tide HAT and LAT The Highest and Lowest Astronomical Tides are the highest and lowest levels that will normally be reached under normal meteorological conditions To calculate this the maximum and minimum values are taken from a continuous 19 year prediction POLTIPS 3 uses basic knowledge of the tides to reduce the time taken to compute HAT and LAT by only predicting the tides around the spring and autumn equinoxes for the years from 1997 to 2015 both known years of extreme tidal levels See also the entry on Extreme Levels High and Low Waters the times in the tidal cycle when the tide reaches its maximum and minimum height respectively The time between successive high waters or successive low waters is about 12 hours 25 minutes for UK ports High and low waters are collectively known as turning points as it is the point in the cycle when the tide turns from ebbing to flooding or vice versa Hourly Heights a type of tidal prediction where the height of the tide is computed at an hourly interval in time and not just for the point of high and low water Mean High Water Neaps MHWN the average level of high water during periods of neap tides Mean High Water Springs MHWS the average level of high water during periods of spring tides Mean Low Water Neaps MLWN the averag
11. date It specifies the percentage down from the top of the box for the top of the date value This defaults to zero If you change the default fonts you will probably need to adjust these values to keep the data evenly spaced within the box Itis best to play around with the relative positioning values until you get something that looks good Page 45 Title Lines Column Lines and Footer Lines are used to specify if you reguire lines drawn to separate the titles the columns of data and the footer This can be set to single line double line dashed line or no line Advanced tab High and Low Water Custom Tide Table Format Xi Font Appearance Advanced Port Name Short name Long name Custom name Datum Information Time Zone Text Shorttext Long text Custom GMT GMT BST Time Zone GMT BST Footer text Tides computed by POLTIPS software developed at Standard Footer the National Oceanography Centre The standard footer text must be used for all published tide tables Port Name will let you select between either a short name the long name or custom text of your choice Examples of this Short name AVONMOUTH Long name ENGLAND WEST COAST AVONMOUTH Custom Avonmouth Port of Bristol The default is for long port name to be selected Only the standard ports in POLTIPS 3 have a long port name If this is selected for a secondary port the short name will be used Datum
12. diurnal tidal regime two high waters and two low waters per day well every 24 hours and 50 minutes The graph below shows the tides for Liverpool 100 90 80 70 60 50 40 30 20 16 92011 177 W2011 High waters and low waters are collectively known as turning points because at these points in time the tide turns from flood to ebb a high water or ebb to flood a low water There are some locations that experience a more complex tidal pattern which can lead to additional turning points occurring Look at the graph below for Southampton a location famous for its double high water s0 45 40 35 30 25 06 12 18 12 18 on do 16 9 2011 17 972011 You can clearly see the double high water in each tidal cycle however between them there is technically speaking anyway a low water Most people would not consider this a real low water as to someone standing at the guayside the tide would still appear to be in Page 27 These additional turning points cause a problem for any tidal calculation software especially if you want to create a traditional style tide table which shows no more than four turning points two high waters and two low waters each day The software must attempt to remove these unwanted turning points whilst leaving the correct ones for inclusion in the tide table This is not difficult for ports such as Southampton or Weymouth a double low water port graph shown below s
13. down cursor keys or the up and down arrows on the toolbar At any time you can switch back to the list view from one of the other views using Output List View or clicking the toolbar button If you save a prediction to disk or copy it to the clipboard it is the list format that is used even if you are viewing another format on screen You can also choose to print the data in this format however for any duration longer that a week or two it could generate a substantial number of pages of output Amore common format for printing is the tide table format Tide table view The tide table view outputs the prediction in a more traditional tide table layout as shown below and is selected with Output Tide Table or clicking on the tide table toolbar button E o New Prediction POLTIPS 3 File Edit View Input Output Misc Help S amka eltel 9 LIVERPOOL GLADSTONE DOCK Datum Chart Datum Year 2015 January February 16 16 F M Time 3 Pa 17 17 Sa Tu NOH Om 18 4 19 Th 18 Su BANGS VON VVOO mowo MOV Pwa ONA OO VONA WOOW 19 M Ba 00 0 00 00 0000 ONON IMO aaoo Bam Ja SB ew zN 20 w 21 w 20 F m 4 1 4 3 2 4 4 5 06 7 9 7 8 9 8 9 7 1 5 3 7 2 5 NOW ONAN AONO NON momo Ron ERUF DONN mo pam 3 O0 MON Coo nO 21 Sa DO COWS O 0 0 0 ONON ONON NW NW ON 120 oao NE ONOG THOR 22 i 100 a 22
14. markers just lines or both are used to display the graph defaults to markers only for high and low waters and lines only for interval predictions If the X axis time axis scaling is set to automatic then POLTIPS 3 will select the appropriate one based on the period of time displayed on the screen When viewing a high and low water prediction it is advisable only to use markers for the plot style as using lines simply joins the points together rather than showing the actual shape of the tide You must use an equal interval prediction to get a sensible plot of the tide between the turning points Format Graphical Output x Graph title 5 Minute Predictions for AVONMOUTH Y axis label Predictions to Chart Datum m Y Axis scaling 5 Plot style Automatic Markers User defined Lines Markers lines Se to EE x axis scaling Marker size Zaim e Weekly Small Cancel Daily Six hourly Grid lines Hourly Grey background The line thickness can be varied by pressing L when the graph is displayed without the dialog box showing Switching between the different views You can switch between list view tide table view and graph view by selecting the appropriate view from the output menu or by clicking on one of the three output buttons on the toolbar Bl S Page 25 Page 26 Locations with complex tidal characteristics Most ports in the UK have a fairly regular semi
15. must have the standard copyright message in the footer If you change the footer text you will get the following warning when you click OK IMPORTANT NOTICE You have changed the footer text on the tide table Please note that you cannot publish tide tables without the standard footer text unless you have written permission from the National Oceanography Centre If you wish to publish tables without the standard footer text you must first seek written permission from the Applications Group at the NOC All the settings are retained between predictions so if you set up a tide table layout you like you can predict multiple ports or periods of time and retain the settings If you want to use the layout at a later date you will need to save the settings to a file on disk see below Custom port name and custom datum statement changes are not stored between predictions as this information could potentially be wrong if a new prediction is made Saving your tide table settings Page 47 Once you get a tide table layout that you like you can save your settings for use with other tide tables for different years or locations Select Output Save Custom Tide Table Format and specify a filename in which all the settings will be stored for later use When you use the program at a later date you can calculate your tidal prediction as normal and then reload your tide table layout again using Output Select Custom Tide Table Format Cu
16. probably need to widen column A to see the data as the date and time will not fit within the default column width AVONMOUTH TZ GMT only Units METRES Datum Chart Datum 01 01 2002 02 49 ta 01 01 2002 08 20 13 44 01 01 2002 15 13 1 19 01 01 2002 20 48 13 23 02 01 2002 03 33 1 16 02 01 2002 09 05 13 44 02 01 2002 15 57 1 25 02 01 2002 21 33 13 11 03 01 2002 04 15 1 31 03 01 2002 09 50 13 25 03 01 2002 16 38 1 41 03 01 2002 22 18 12 79 04 01 2002 04 54 1 54 04 01 2002 10 37 12 88 04 01 2002 17 18 1 66 7 Onceyou have the data in this form you will be able to use many of the excel functions to derive additional statistics and information about the tide produce freguency distributions or use the chart wizard to produce graphs Seriesi 0 30 12 2001 00 00 04 01 2002 00 00 09 01 2002 00 00 14 01 2002 00 00 19 01 2002 00 00 24 01 2002 00 00 29 01 2002 00 00 03 02 2002 00 00 Page 57 Time and Tide Tides are the alternating rise and fall of the surface of the seas and oceans They are due mainly to the gravitational attraction pull of the moon and sun on the rotating earth Two high and two low tides occur daily around Britain and with average weather conditions scientists can predict their movements with considerable accuracy Both moon and sun affect the tides but since the moon is much closer to the earth 240 000 miles instead of 93 000 0
17. traditionally made to Greenwich Mean Time also called Universal Time This is the local time for all UK ports However the UK switches to British Summer Time BST for 7 months of the year which is GMT 1hour You can select BST by ticking this box on the input dialog BST correction is only supported for high and low water predictions and not for interval predictions Turning Points see high and low waters Page 77 Table of Standard Harmonic Constants No Name No Name No Name No Name 1 Sa 30 OP 59 25Me 88 3MNg 2 Ssa 31 M2 60 MSKe 89 Ms 3 Mm 32 MKS2 61 2MN2S2 90 2MSNe 4 Msf 33 de 62 3M SK 91 3MS4 5 Mf 34 Le 63 3M2S2 92 3MKs 6 201 35 T2 64 MNK2S2 93 MSNKg 7 c sigma 36 S2 65 SNK2 94 2 MS s 8 Q 37 R2 66 2SK2 95 2MSKs 9 p ho 38 Ke 67 2MS N gt 96 4MSi0 10 Ol 39 MSN2 68 MQs 97 3M2S10 11 MP 40 Kua 69 2MP3 98 4MSNi2 12 M 41 2SM2 70 2MQ3 99 5MSi2 13 chi 42 MO3 71 3MK4 100 4M2S12 14 m pi 43 Ms 72 3MS4 101 MVS2 15 Py 44 SO3 73 2MSKa 102 2MK2 16 S 45 MK3 74 3MKs 103 MA 17 K 46 Sk3 75 Ms 104 MB 18 y1 psi 47 MN4 76 3MOs 105 MSV 19 1 phi 48 Ma 77 2MN Ss 106 SKMe 20 6 theta 49 SN4 78 3MNS6 107 2MNS4 21 J 50 MS4 79 4MKe 108 MV4 22 SO 51 MK 80 4MS6 109 3MN4 23 00 52 S4 81 2MSNKs 110 2MSN4 24 OQ2 53 SK 82 2MV6 111 NA 25 MNS2 54 2MN6 8
18. you will need to install it manually Copy the moonsym ttf file from the CD into the fonts folder inside your windows folder you will need to be logged on as administrator to do this The software did not appear to install correctly If you are having problems running the software after installing it please make sure you are logged on as administrator when you install it You should also try uninstalling any previous versions of the software and then try to reinstall the CD If you still have problems contact the Tidal Prediction Service at the National Oceanography Centre Ports with complex tidal patterns Some ports have unusual tidal characteristics e g Bournemouth Cowes Poole Portland Southampton and Weymouth If you use POLTIPS 3 to do predictions for any of the above ports please read the section Locations with unusual tidal characteristics on page 27 Page 12 The POLTIPS 3 Window New Prediction POLTIPS 3 File Edit View Input Output Misc Help ajaj gt am tel 94 Software Licenced to POL Licence duration 2008 to 2011 POL in house version Single user licence PO LTI PS e 3 Custom tide table feature enabled Use of own harmonic constants enabled ver 3 5 0 0 11 The picture above shows how the POLTIPS 3 should first look when you start the program Interaction with the program is done through the options on the program menu however more commonly used controls have a button on th
19. 00 miles it has more than twice the effect of the sun even though it is much smaller So to understand tides it is best to start with the moon and the lunar tide before looking at the effect of the sun As everyone knows the moon orbits around the earth However the earth is not fixed rigidiy in space and as the moon orbits it attracts the earth round in a monthly orbit of its own So the earth has a small orbit caused by the moon in addition to its annual one round the sun It is the gravitational pull of the moon on the earth that keeps the earth in its monthly orbit This is just the same as when you whirl a weight round on a piece of string It is only by constantly pulling on the string that you prevent the object from flying off If you stop pulling completely by letting go on the string the object does fly off Gravity acts in the same way as you pulling on the string and prevents the earth from flying off However unlike the string the attractive pull of gravity gets weaker as the distance between the objects increases and it becomes stronger of course the closer they get The earth is large so the pull of gravity on the side of the earth nearer the moon is stronger than the pull on the side of the earth farther from the moon The pull of the moon s gravity is just enough to keep the earth in its monthly orbit but it is a bit stronger on the surface of the earth facing the moon near side and weaker on the far side Thi
20. 14 1 148 181 100 222 257 287 205 219 278 219 15 100 rT 0 49 081 075 12 17 2m 278 14 2 08 273 2 Additional Key Options Press G Toggles the gap fill characters on off Press F Changes between 3 pre defined fonts Page 41 Page 42 Custom tide table format One of the features of POLTIPS 3 available only on the customised and UserData licence is the ability to customise your own high and low water tide table layout To access this make a high and low water prediction as normal and then select Output Custom Tide Table HLW The default layout for custom tide tables looks like the picture below Donnain ram a inizi Fe Eat Vem Fe Ope Me Pip nlaj x simmo lelrllala 2 ENGLAND WEST COAST AVONMOUTH GMT Lat 51 30 N Long 2 43 W Year 2002 Jaruary February March Apel fod Sinead Eo peel Bree h Me ri Lond gy om om ge ipone gen Sid S416 ee win we SE ge Sie Se v ge olagan alg a tejag ym aeg ee i de vap ger vep g om ve 4 19 4 nie ir Mp 19 4 ee 5 20 5 20 ve ve 20 5 20 To change this layout select Output Format Tide Table to bring up the dialog box shown below As there are many settings that can be changed they have been split across three tabs called Font Appearance and Advanced shown below When you make any changes to the settings click either the Apply button to see the effect of the changes without closing the dialog box or the OK but
21. 3 3MSK6 112 NB2 26 2N2 55 Me 84 4MN6 113 MSOs 27 ye mu 56 MSNe 85 3MSNs 114 MSKs 28 Ne 57 2MS6 86 MKLs 115 2MN2 29 ve nu 58 2MKs 87 2 MN s Some harmonic constants have alternative names No a Ee as ne a known as No a mas as 24 OQ MNK2 44 SO3 104 MB MSP gt 30 OP MSK2 103 MA MPS gt Page 78
22. 6 12 14 06 43 19 14 12 48 07 17 19 47 13 23 07 48 20 18 13 57 08 18 20 46 14 34 08 48 21 17 15 13 09 24 21 53 15 58 10 06 22 38 16 55 E 11 00 23 38 18 07 aias 12 17 19 24 00 57 x 13 41 20 30 02 12 14 49 21 24 03 13 15 48 22 12 04 06 16 42 22 57 04 57 17 32 23 40 05 44 e 18 20 HEHH 06 30 19 06 12 42 07 13 19 49 13 26 07 54 L 20 31 14 10 08 36 21 12 14 57 09 17 21 54 15 48 10 03 22 43 16 50 10 58 23 45 18 09 HEHE 12 12 19 35 01 03 13 40 20 49 02 24 15 02 21 47 03 33 16 09 Times are GMT Datum Chart Datum National Oceanography Centre www noc ac uk Copyright Reserved Additional Key Options Press L Toggles the grid lines on off Press G Toggles the gap fill characters on off Press F Changes between 3 pre defined fonts Page 40 Additional fixed format 3 This format is a landscape format for high water or low water only predictions It is a four month per page format that is popular with publishers as the 4 monthly columns can be split up onto separate pages of a small booklet Time Zone GMT Tidal Predictions LOW WATERS 2011 Units METRES Datum of Predictions Chart Datum 4 93 metres below Ordnance Datum Newlyn Batisn Summer Time Datos for 2011 270 March to 30 October data not aqlusted LIVERPOOL GLADSTONE DOCK LIVERPOOL GLADSTONE DOCK LIVERPOOL GLADSTONE DOCK LIVERPOOL GLADSTONE DOCK January April Noming me m 0426 208 0500 179 oss 1 58
23. 8 24 8 57 8 87 9 10 9 23 8 87 8 80 8 67 8 48 8 23 7 93 7 59 7 27 7 08 Afternoon H M 2055 2151 2240 2323 RK ORK 1214 1248 1323 1357 1434 1513 1558 1655 1807 1924 2030 2124 2212 2257 2340 ROKK 12 42 13 26 1410 1457 1548 1650 1809 1935 2049 2147 Height Metres 8 33 8 55 8 75 8 85 xxx 9 25 9 18 9 03 8 81 8 51 8 15 7 75 7 40 7 22 8 19 8 67 9 10 9 42 eK 9 89 9 86 9 64 9 24 8 72 8 14 7 70 7 61 7 86 8 21 Datum Chart Datum Copyright Reserved This tide table format is for calculations of just the high waters or just low waters It is a one month per page format that separates the tides into morning and afternoon columns It will put asterisks into the column if there is no tide in that half of the day Page 39 Additional fixed format 2 This tide table format is a one month per page format for both high waters and low waters data Using a grid it clearly separates out the high waters and the low waters and then subdivides the columns into morning and afternoon tides o New Prediction POLTIPS 3 File Edit View Input Output Misc Help SS gt amS llre e LIVERPOOL GLADSTONE DOCK JANUARY 2011 High Water Low Water Morning Afternoon Morning Afternoon Time m Time m Time m Time m 8 24 20 55 8 33 02 42 243 15 10 21 51 03 44 16 13 22 40 04 38 17 08 23 23 05 24 17 55 HEHH 06 06 18 3
24. Information also has the option of short text long text and custom text The long text which is the default gives the datum selected relative to the other principle datum For example Short text Datum of Predictions Chart Datum Long text Datum of Predictions Chart Datum 6 50 metres below Ordnance Datum Newlyn Custom CHART DATUM 6 5m below Ordnance Datum Be wary of using custom datum statements in case you specify incorrect information Page 46 Time Zone Text allows you to select between the following two formats Selected Displayed if BST not selected Displayed if BST selected GMT GMT BST GMT GMT BST Time Zone GMT BST Time Zone GMT only Time Zone GMT BST Note that the text displayed is based on whether BST was selected when the prediction was made and not on which months are displayed on screen For example if you predict a whole year with BST selected and opt to display two months per page page one which will contain January and February predictions will display GMT BST even though BST does not start until March This is for consistency across all pages of the tide table Footer Text enables you to change the line of text that appears below the datum statement at the bottom of every page This defaults to the standard NOC copyright message Although this can be changed within the program the condition for publication of tide tables produced by POLTIPSs3 is that it
25. MT only Predictions to Charl Datum m w 6 00 3 6 0 w 17 92011 18 9 2011 19 9 2011 20 9 2011 21 9 2014 end ood 2 With the mouse right click on the blue dot representing the turning point you no longer require i e the one POLTIPS 3 has wrongly selected It will be ringed to show you have selected it Page 31 3 Hold shift down and with the mouse right click on the red tide you want to use in its place These should be adjacent low waters or adjacent high waters Since turning points always alternate between high water and low water the two selected dots must be two dots apart 4 Press S to swap them The red and blue dots will change places and the new blue dot will now be the one shown on the tide table outputs High and Low Waters for CHRISTCHURCH PRIORY QUAY Time Zone GMT only i i 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 20 9 2011 kx Note that you can only swap two adjacent high waters if the low water between them is not selected i e it must be a red dot Likewise swapping two adjacent low waters must have a non selected high water between them Not having this rule would permit the tides to go out of sequence and you could end up with two high waters next to each other in the tide table rather than maintaining the alternating high low high low sequence Page 32 Tidal statistics From the Tidal Pred
26. POLTIPS 3 ver 3 5 1 User Guide NOTE TO PUBLISHERS If you intend to publish the tides computed by POLTIPS 3 please ensure that you read this user guide carefully that you fully understand how to use the software and have a good understanding of tides Installation of POLTIPS Please read the installation instructions on page 11 before attempting to install this software National Oceanography Centre Q 0151 795 4800 Joseph Proudman Building c 0151 795 4905 6 Brownlow Street Liverpool L3 5DA applications noc ac uk Page 2 Contents COMLEM S etc leme dem Haaa ann Maine ide lame aaa yen dad anna saab akal an T 3 Warrantyandliability 11 5 gh ge Ve e KN A YY MY e 7 TheNationalOceanographyCentre 7 TheApplicati ns TEAM e see errian enrenar ae eaan a errara earan Enae RESEN ER dinlen 7 POLTIPS 3tidalpredictionssoftware 8 What are the differences between the Standard Custom Publishers and UserDataversionsofPOLTIPS eee 8 Publishingtidalpredictiononthelnternet 9 Hardware Requirements aianei adin enean aeaea a accede EDA 9 Prediction Method Sisirain a E EEE alsada iyiyi 9 Conventionsusedinthismanual 10 InstallingandstartingPOLTIPS 3 11 How to instal
27. able to download from our web site 4 NOC will endeavour to contact all registered customers preferably by e mail informing them that a new update has been placed on the web ready to download 5 NOC will provide technical support for POLTIPS 3 only to its registered users 6 Wedo not guarantee that the functions contained in POLTIPS 3 will meet your requirements or that the operation of the program will be either error free or appear precisely as described in any documentation describing POLTIPS 3 7 Noresponsibility can be accepted by NERC for any consequential loss or damage arising from any use that is made of POLTIPS 3 and output from POLTIPS 3 howsoever caused 8 Allimplied warranties terms representations and conditions including by way of example only the implied conditions of satisfactory quality and fitness for any purpose of the information are excluded to the fullest extent permitted by law 9 This Agreement is governed by English law and the parties submit to the exclusive jurisdiction of the English courts Please ensure you read the warning in the box on page 20 regarding the calculation of tides for locations with a complex tidal regime Please also read the full terms amp conditions given on a separate sheet included with the software Page 5 Page 6 Introduction The National Oceanography Centre The National Oceanography Centre NOC is a component laboratory of the UK s Natural Environment Res
28. aches in the selected time period Lowest Tide in period the lowest level the tide reaches in the selected time period Largest Tidal Range in period the biggest difference that occurs between a high water and an adjacent low water in the selected time period Average Flood time the average time taken for the tide to come in i e average time between low water and the next high water Average Ebb time the average time taken for the tide to go out i e average time between a high water and the next low water Quickest Flood time the fastest time that the tide comes in in the selected time period Using the map POLTIPS 3 can display a map of the UK and the ports simply by selecting InputSShow Map or clicking on the toolbar button si When the map is first displayed only a selection of the ports available in POLTIPS 3 are shown However you can zoom in to a smaller area of the coast using either the zoom buttons on the toolbar AJA or using the left mouse button to drag a rectangle over the area of the map you are interested in o w Prediction POLTI File Edit View Input Output Misc Help hiria 2 TOW SW BW TW BW sw ew SW Zoom Level 1 As you zoom in more ports will be displayed and the zoom level will be displayed in the status bar along the bottom of the window as Zoom level 1 through to Zoom level 5 all ports shown Page 35 The reason for the blue shaded cro
29. an the tide be predicted Since the tide is caused by the astronomy of the earth moon sun system which is known very accurately and can be predicted well into the future the tides can also be predicted well into the future So if you want to plan your sailing club events for the year 2025 get in touch and for a small fee the Applications Team can provide you with the tide table Page 66 When trying to predict well into the future we have to take into account the rise in global sea level The further into the future we try and predict the more significant this effect can become 3 What causes tides Tides are caused by the effects of gravity in the earth moon sun system and the movement of those three bodies within the system If you imagine that the earth is completely covered in water there are two bulges of water one towards the moon and another on the opposite side see question 4 The rise and fall in sea level is caused by the earth rotating on its axis underneath these bulges of water There are two tides a day because it passes under two bulges for each rotation 24 hours see question 7 This is called the lunar tide Two bulges of water are also caused by the sun called the solar tide and these can either reinforce or partially cancel out the lunar tide to give spring and neap tides see question 8 4 If gravity is always pulling towards the moon what causes the bulge on the opposite side of the earth This
30. and low water tide table and is available only when the interval is set to 60 minutes this is often called an hourly height table Note that all times for equal interval predictions are given in GMT UTC only British Summer Time BST is not supported ose reann FOUTS aaa eee Fie Edt View Input Opt Mec Heb lett aj a alya 2 ENGLAND WEST COAST AVONMOUTH TME ZONE GMT Lat STIN Long ZAT UNITS METRES JANUARY 2002 B L avause as Pm7iTe PLaveve Varaz Bxroes ese Five OLareze Copyright Reserved Dasem of Predictions Chart Datum 6 50 metres below Ordnance Datum Newtyn Prowdman Oceanographic Laboratory Bidston Observatory Birkenhead Merseyside UK Ready As with the high and low water tide table the full width of the window is used meaning that you may need to scroll up and down with the arrow keys or toolbar buttons to see the whole table Page 19 When printing the hourly height tide table you must set the printer to landscape mode rather than portrait If you forget to change this you will get a Warning message appear and printing will not continue until this has been changed Output precision and units The output precision on the list view and the tide table view can be setto 1 2 or 3 decimal places the default being 2 Note that although the data can be output to 3 decimal places it does not imply that the data is accurate to 3 decimal places as there are many fact
31. ater would be roughly the same for all points on the coast but it isn t The problem is caused by the land that gets in the way of the moving water As the earth rotates the water has to move to generate the high tides but because of the shape of coastlines and the variation in sea depth bathymetry there is a lag Every location has a unique coastline and bathymetry that gives each location its unique tidal pattern 6 How often do high tides occur In UK waters approximately every 12 hours 25 minutes You may wonder why it is not exactly 12 hours but you must remember that the moon is also orbiting around the earth By the time a point on the earth s surface has rotated from point x to point y 12 hours the moon has also moved a small amount so the earth has to rotate for an extra 25 minutes from point y to point z to be under the high water bulge Page 68 7 Are there always two high tides a day No Although most places in Britain experience approximately two tides a day semi diurnal there are some places which experience what is known asa double high water e g Southampton or double low water e g Portland This is caused by the shape of the coastline and the bathymetry sea depth Even for well behaved locations when you look at a tide table you will see that some days only have 3 tides This is because the average time between high water and low water is 6 hours 12 minutes and not exactly 6 hours Therefore o
32. ations in POLTIPS or Input Sunrise Latitude oe and sunset by lat long to specify any j Longitude 9 0 East location lt 1 C West Year Height above sea level Set the parameters in the dialog and click m P E nates on the Compute Now button After a aes couple of seconds the table giving sunrise and sunset times will be displayed This can be scrolled in the same way as the tide table using the arrow keys or toolbar buttons o New Prediction POLTIPS File Edit View Input Output Misc Help DEE EEE Sunrise and Sunset Times Times in GMT ABERDEEN Year 2001 January February March 1 0847 15 36 1 08 08 16 36 1 07 02 17 40 2 08 46 15 38 2 08 06 16 38 2 06 59 17 42 3 08 46 15 39 3 08 04 16 40 3 06 56 17 44 4 08 46 15 40 4 08 02 16 43 4 06 54 17 47 5 08 45 15 42 5 08 00 16 45 5 06 51 17 49 6 08 45 15 43 6 07 57 16 47 6 0648 17 51 7 08 44 15 45 7 07 55 16 50 7 06 46 17 53 8 0843 15 47 8 07 53 16 52 8 0643 17 56 9 08 42 15 48 9 07 51 16 54 9 06 40 17 58 10 0841 15 50 10 07 48 16 57 10 06 38 1800 11 0840 15 52 11 07 46 16 59 11 06 35 18 02 12 08 39 15 53 12 07 44 17 01 12 06 32 18 04 13 0838 15 55 13 0742 17 04 13 06 29 18 06 14 08 37 15 57 14 07 39 17 06 14 06 27 18 09 15 08 36 15 59 15 07 37 17 08 15 06 24 18 11 16 08 35 16 01 16 07 34 17 10 16 06 21 18 13 17 08 33 16 03 17 07 32 1713 17 0619 18 15 18 08 32 16 05 18 07 30 17 15 18 06 16 18 17 1a n231 AN 1a 07 07 17 17 1a ne 12 19 90
33. d Page 7 services it offered was greatly expanded to include the results of the latest NOC scientific research However oceanographic research tends to produce vast amounts of raw data with little meaning to anyone other than a trained oceanographer The Applications Team mission is to provide a value added service which includes ensuring that the customer gets the data they require in a form that is easily understood This is achieved by creating visualisations of the data fully documented reports or by processing the raw data to derive new data sets that are of more value to users in the real world The Applications Team also develops software that allows users to buy raw data that remains hidden behind a friendly user interface and carries out all the processing necessary to produce attractive and informative displays which can be easily printed or exported into other software POLTIPSe3 tidal predictions software POLTIPS is one such product developed by the Applications Team First released in 1993 as a DOS product for PCs its success has led to successive refinements and the inevitable move to the Windows environment The current version of POLTIPS is by far the most powerful and user friendly version to date Hidden behind the simple to use interface is a powerful mathematical engine for computing the tides combined with sophisticated graphical layout tools for producing tide tables and graphs of the tide Combine
34. d data to analyse for example ports on the National Tide Gauge Network or locations of particular scientific interest A few standard ports have guite a complex tidal pattern that cannot be accurately reproduced just using harmonic constants These ports have additional factors called shallow water corrections used to make small adjustments to the high and low water times and heights Equal interval predictions cannot be made for ports with shallow water corrections Secondary Ports There are many locations around the coast where long periods of tidal observations do not exist Predictions for such locations are computed by making a prediction for a nearby main port and then applying time and height differences to the high and low waters Each secondary port has 4 separate time differences depending on whether high or low waters are being predicted and on the time of day There are also 4 height differences for mean high and low water springs and neaps Equal interval predictions cannot be computed for secondary ports Conventions used in this manual File Print means from the File menu select Print abcdefg means you type this text in san X means hold down the shift key and press X en X means hold down the control or ctrl key and press X Page 10 Installing and starting POLTIPS 3 How to install POLTIPS 3 Please read before installation Insert the POLTIPS 3 CD into your optical drive
35. d with NOC s internationally renowned reputation for accuracy POLTIPS is one of the most powerful tidal prediction programs available What are the differences between the Standard Custom Publishers and UserData versions of POLTIPS Due to the different requirements of the wide variety of POLTIPS users we have created three different versions of POLTIPS 3 They are basically the same program but have certain restrictions imposed The standard version can be bought with either a three or five year licence and contains around 700 UK ports This has a slightly reduced accuracy over both the NOC in house predictions and the custom publishers version of POLTIPS 3 Users of the standard version are not licensed to publish the data in any form however the tide tables can be distributed free of charge within a membership club e g a sailing or fishing club Users cannot use the custom tide table layouts or their own harmonic constants with the software Page 8 Although the accuracy is slightly reduced compared with the customised version it is still suitable for the majority of applications For consultancy or engineering use we recommend the custom version The custom publishers version is purchased on an individual port basis with either a two or three year licence Users are permitted to publish the tide tables for resale in any number of books for which they own the complete copyright i e users cannot purchase this software and then se
36. e toolbar to provide guicker access This screen also gives information on your licence and restrictions on the use of the software The first line gives the company name the software is licensed to Do not give copies of the software to other people as it will have your company name embedded within the software The licence duration is the period for which predictions can be made Note that the software can be used outside of this period but it will only make calculations for the years specified The third line specifies whether you have a standard customised or UserData licence see page 8 and whether this is a single user licence or a network licence Page 13 The last two lines specify whether the custom tide table feature is enabled see page 43 and whether you are licensed to use your own sets of harmonic constants with the software see page 48 Toolbar The buttons on the toolbar are i save the prediction to a text file on the disk E print the display currently on screen copy the prediction data to the clipboard 5 display the map E set the input parameters for the prediction 1 display the prediction in list format display the prediction as a tide table Pel display the prediction as a graph gt t alej scroll and zoom buttons about POLTIPS 3 Page 14 Using POLTIPS 3 This section takes you through what you need to know to produce your first printed tide table Setting the param
37. e level of low water during periods of neap tides Mean Low Water Springs MLWS average level of low water during periods of spring tides Mixed Tide tides that are neither totally semidiurnal or diurnal however one or the other is usually predominant Page 75 Neap Tides tides that usually occur around the time of the first and last guarters of the moon and have a smaller than average tidal range Semidiurnal Tides tides that have two high waters and two low waters every 24 hours 50 minutes Nearly all the tides around the UK are of this type Shallow Water Influence a value that indicates how much shallow water effects influence the overall tide See table below Value Description less than 0 1 small influence tide should have a typically sinusoidal profile 0 1 to 0 2 moderate influence tide may show slightly unusual features particularly during neap tides 0 2 to 0 3 significant influence tide is complex and will probably have more than 4 tides per day see the section on locations with unusual tides on page 27 greater than 0 3 very significant influence tide will have a very unusual profile possibly switching between semidiurnal and diurnal tides Will certainly show more than 4 tides per day see page 27 Spring Tides tides that usually occur one or two days after new and full moon and have a larger than average tidal ranges Surges the movemen
38. e prediction for 2 days might look File Edit View Input een Misc Help B S AFE l gt lalaj 2 5 Minute Predictions for AVONMOUTH Time Zone GMT only 140 13 0 120 11 0 10 0 9 0 8 0 7 0 6 0 5 0 40 30 20 Predictions to Chart Datum 10 0 06 12 18 D 06 12 18 1 1 2002 21 1 2002 When viewed in list view you get 576 values however this is much easier to grasp when you look at it as a graph Notice that the intervals plotted on the time axis vary automatically depending on how much is displayed When viewing a month you only get the date of each Sunday displayed However with 2 days in view you get every 6 hours Zoom in further and the graph will show every hour Formatting the graph view Many of the automatic settings on the graph can be changed for example you can remove the grey background from the graph for clearer printing To do this select Output Format Graph Page 24 From this dialog box it is possible to change various aspects of the graph e the title along the top of the graph e the text displayed along the vertical Y axis e the maximum and minimum values for the vertical axis e the interval for the time axis default is automatic e the size of the markers default is small e whether you want grid lines shown on the graph e whether you want the grey background on the graph e whether just
39. e to the gravity of the moon e 24 00 and 24 50 28 328 cycles caused by the differences in the two tidal bulges e 27 2122 day cycle caused by change in lunar declination Moons angle to the Earth e 27 5546 day cycle caused by a regular change in the Earth Moon distance e 29 5306 day cycle caused by the phases of the moon see question 8 Each of these cycles is called a tidal harmonic constituent and POLTIPS uses in excess of 100 of them in calculating a tide table You can see that the length of these cycles is known very accurately to the nearest 1 1000 of a second Therefore it is easy to find them in a seguence of observations using a method called tidal analysis Once each constituent is identified its size amplitude and time of arrival phase is stored These two values known as a harmonic constant are unigue for every location The amplitude and phase for each constituent combined with the fixed speed of that constituent allows us to predict its contribution to the overall tide forward or backward in time almost indefinitely Adding up the effects of all the constituents at a given location lets us predict the overall tide at any time in the future or past Page 71 Most tide tables just list the time and height when the water is at a maximum and minimum level in each tidal cycle This leads to approximately 2 high waters and 2 low waters every 24 hours 50 minutes or 4 tides a day on most days with 3 tides on every
40. earch Council NERC The offices of the Liverpool Site of the National Oceanography Centre iz the other site being based in al Southampton Around 100 people work in the Liverpool office The NOC has provided a national and international tidal prediction service since 1924 in fact the modern methods of tidal prediction used throughout the world are based on the work of Dr Arthur Doodson in the 1920s and who later became Director of the laboratory Since then NOC has continued to develop and refine the analytical methods used to compute the tides Coupled with advances in modern computer hardware and software we now have the most accurate tidal prediction software available As the laboratory responsible for the installation maintenance and running of the UK s National Tide Gauge Network we have access to the most accurate and up to date data which we utilise to derive harmonic constants used in the computation of tide tables Although some methods of tidal prediction use only a few harmonic constituents the National Oceanography Centre uses up to 150 harmonic constants for some main ports hence producing what NOC believes to be the most accurate tidal predictions available The Applications Team The National Oceanography Centre has since the 1920s had a team of tidal experts produce tide tables for organisations all over the world In 1992 the group was renamed The Applications Team and the range of data an
41. elop its world renowned reputation in tidal prediction by developing new analytical Page 64 methods for locations that had a reputation for being difficult to predict accurately By this time ocean research had moved on to encompass the much harder to predict surge component of sea level the change in level due to meteorological effects such as wind and atmospheric pressure The computer model run twice a day at the UK Meteorological Office to predict surges around the coast was developed by scientists at NOC In 1992 the Tidal Computation and Statistics Section became known as the Applications Group and the work branched out to include offshore tidal predictions based on sophisticated computer simulations of the worlds seas and oceans In 1994 the first version of the POLTIPS tidal prediction package was released for the PC and could predict a yearly tide table in less than 10 minutes The latest Windows version of the software to which this user guide accompanies can carry out the same task in less than 5 seconds on a typical modern PC In 2004 the laboratory moved from it s home in Bidston to a new building on the University of Liverpool campus It is incredible to think how far we have come over the last 80 years with the help of computing technology And even though we know a lot about the tides we are just beginning to fully understand the other processes that go on within our seas and oceans Page 65 Freguentiy As
42. erval prediction is one that gives the height of the tide at certain equally spaced time intervals for example every 15 minutes or every hour rather than at the specific time of high and low water Using this type of prediction you can see how the tide changes over time Equal interval predictions are only available for standard ports not secondary ports see page 9 If you ask POLTIPS 3 to compute an equal interval for a secondary port you will be asked whether you would like to use the reference standard port or whether you would like to change to high and low waters for your selected port Select the option you require to continue or cancel the prediction Page 18 More information reguired The location you have selected is a secondary port The only information POLTIPS has available for secondary ports are time and height difference of high and low water relative to a standard port usually a nearby location and one with similar tidal characteristics Please select one of these options to continue or click cancel Compute the high and low waters for the selected location Compute the requested interval for the reference location Continue with selected option Cancel prediction The list view for equal interval predictions is the same as for high and low waters however the time intervals are equally spaced The tide table view for equal interval predictions is completely different from the high
43. eters for the prediction Before you can compute the tides you need to tell POLTIPS 3 where you would like the tide table for the duration of the tide table and the type of prediction Select Input amp Tidal Predictions to bring up the dialog box shown below Tidal Predictions xj NO PORT SELECTED 2 4 8 4 2001 p End date mma 7 days This Month This Year r Type of prediction Port Name Start date High and low waters ANNAN WATERFOOT C Equalintervel 80 mins ANSTRUTHER EASTER APPLECROSS High waters only APPLEDORE eit ARBROATH ow waters only ARDGLASS ii SL ARDNAVE POINT ka 8 Cancel Show on map I Adjustfor British Summer Time BST First select the port you require from the list of ports You can either scroll down the list using the arrows and scroll bar or just start typing the name in the box and the list will scroll automatically to the right place Once you see the port name in the list click on it Now set the start and end date of the prediction you require in the date boxes either by typing in the number directly or using the up and down arrows next to each box Alternatively just click on one of the three preset buttons to make a prediction for the next 7 days the current month or the current year The dates will be filled in automatically for you Page 15 Then select the type of prediction you reguire from the choice of five types The default i
44. hart and Ordnance datum by selecting Output Datum and choosing the one you require The currently selected datum is displayed on both the list view and the tide table view ix Format List View Formatting the List View Date separator m Time separator p Field separator ey 9 2 spaces n space One of the main uses of the list view W tab 1 space R 4 tab is for getting the tide data into wil imz another Windows application such as Microsoft Excel spreadsheet To allow for more flexibility POLTIPS 3 As number C As word Month display eading zero on dates OK Leading zero on hours gi Cancel Page 21 will let you change the format by selecting Output Format List View This is only available when the list view is selected for the current prediction This dialog gives you the capability to change the date and time separator characters and the field separator the characters between the date and time and the time and height You can also specify whether the month is displayed as a number or 3 letter abbreviated word and whether you require leading zeros on the dates and time only the hours as the minutes always use a leading zero The options set in this dialog box are also used when tide data is copied to the clipboard or saved into a text file see the next section Saving tidal data to disk or the clipboard Although POLTIPS 3 has a powerf
45. he precise scaling for prints on A4 paper is 12 085 but multiplying by 12 is close enough for all point sizes below 24pt Appearance tab This tab allows you to adjust some of the more common properties that affect the appearance of the tide table Tides allows you to select whether you want just high waters just low waters or both of them default You can also turn both of them off although this would not leave much in the way of data Show gives you the option of displaying the days of the week the location of the port as a latitude and longitude the moons phases and the time and units of height metres or feet on the tide table Page 44 High and Low Water Custom Tide Table Format Font Appearance Tides High Waters IV Low Waters Months per page s C3 g Advanced Show IV Days of week T Moons phases Columns per month C162 we Relative positioning offset Date 26 J Date V Time so Height MW Port location lat Jong M Time and height units Title Lines None Single Dash Double Column Lines None Single Dash Double Footer Lines None Single Dash Double oe cores It is advisable to always have the units of height shown if you intend to publish the tide table If you turn this off you should ensure that it is displayed elsewhere on the page Months per page lets you select between
46. her possibility is that it is related to the natural feature of a spring which isa place where water wells up from the earth 10 Where are the highest tides in the world Burncoat Head in the Bay of Fundy Canada has an average spring tidal range of 12 9 m The second largest tides in the world occur at Avonmouth in the Bristol Channel where the average spring range is 12 3 m The average spring tidal range is the average difference between high and low waters during spring tides 11 Do the tides follow a repeated pattern No There are similarities for example every 18 6 years we experience larger than average tides but they never actually repeat 12 When during a year can we expect to find the largest tides A day or two after the full or new moon nearest to the equinoxes The spring equinox is usually the 21st March and the autumn equinox the 23rd September Some years have tides that are notably higher than other years 1997 was a significant year as will be the year 2015 For really favourable conditions you will have to wait around until the year 3182 Even then the tides may only be 1 or 2 cm higher than in 2015 13 Do the planets have any affect on the tides The tidal force generated by a body in space is based on two things its mass and its distance from the earth and it is the latter of these that is far more significant The nearest approach of Venus to earth is still more than 100 times further awa
47. ictions input dialog box you can select to have POLTIPS 3 compute some general statistics about the tide at the selected location ar ama KAF amy 7 days This Month This Year m Type of prediction C High and low waters C Equal interval eo mins High waters only Low waters only Click this Statistics option Cancel Show on map I Adjustfor British Summer Time BST Standard port New Prediction POLTIPS 3 File Edit View Input Output Misc Help S alm ols iris lealej e Tidal Statistics for AVONMOUTH Latitude 51 30 N Longitude 2 43 W Port details Standard port Datum of Predictions Chart Datum 6 50 metres below Ordnance Datum Newlyn Highest Astronomical Tide HAT 14 65 metres HAT occurs at 08 50 GMT on 21 02 2015 Lowest Astronomical Tide LAT 0 21 metres LAT occurs at 15 05 GMT on 10 03 1997 Maximum Tidal Range possible 14 79 metres High Water Spring MHWS 12 75 metres High Water Neap MHWN 69 metres Low Water Neap MLWN 16 metres Low Water Spring MLWS 09 metres Type 02 semidiurnal Shallow Water Influence 08 Selected Period 01 10 2001 to 31 10 2001 Highest Tide in this period 14 26 metres Lowest Tide in this period 0 30 metres Largest Tidal Range in this period 13 96 metres 5 hours 52 minutes 6 hours 32 minutes To save the information in a file select either File Save as Text File click on the save button on
48. igh and Low Waters for WEYMOUTH Time Zone GMT only Predictions to Chart Datum m 18 19 20 21 22 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 01 02 03 04 27 9 2011 28 92011 In the case of Weymouth a double low water port shown above if POLTIPS always picked the lowest low water the data would jump about between the first and second low waters meaning on one tidal cycle you could have a5 hour ebb tide and on the next an 8 hour ebb tide On certain occasions POLTIPS may identify the wrong principle turning points For example in the graphs on the following page showing the tide for Christchurch a double high water port POLTIPS has selected to pick the first high water as the main one However over the course of a few tidal cycles the significance of the first high water diminishes and for a few days the first high water is considerably lower than the second If producing a tide table it is sometimes desirable to swap one of the selected tides shown in blue with one of the removed tides shown in red This should be done with extreme caution and only if you fully understand what you are doing To do this follow these steps 1 Zoom in on the area so that the dots on the graph are clearly separated Fle Edt Vem Input Ost Mec ep ulaj a ammor Jala 9 High and Low Waters for CHRISTCHURCH PRIORY QUAY Time Zone G
49. ighest high waters and the lowest low waters Extreme Levels the term used to describe levels higher than HAT or lower than LAT caused by meteorological conditions These can only be derived statistically and are usually quoted as the still water level that is likely to appear once every so many years Example of Extreme Levels for Dover Highest Astronomical Tide 7 23m 10 year extreme level 7 74m 100 year extreme level 8 21m 1000 year extreme level 8 80m 10000 year extreme level 9 47m Extreme level information is available from NOC for many coastal and offshore locations Flood Tide the landward tidal flow from low water to high water The Flood time is the time between low water and the following high water GMT UT see Time Zones below Harmonic Constants the amplitude and phase of the various harmonic constituents that can be added together to calculate the overall tide See How can tide tables be produced so accurately in the Frequently Asked Questions section of this manual for more details Every location has a unique set of harmonic constants which are derived from tidal analysis of observations for that location Page 74 Harmonic Constituents the tide is influenced by many factors and each one of these can be represented mathematically by one or more simple sine wave functions Each one of these mathematical waves is called a harmonic constituent of the tide There
50. in the INDEX DAT file To access them you will need to place an entry in the index file for them to appear in the POLTIPSs3 input dialog box or copy the file INDEXUSR DAT over the INDEX DAT file Licence Restrictions Users with a standard POLTIPS 3 licence cannot use this feature Users with a customised version of POLTIPS 3 will be able to make predictions using their own constants for the same period as their licence Page 53 Users with a UserData licence for POLTIPS 3 will usually have a 10 year licence this will have been specified when you purchased the software Showing your port on the map If you wish for your port to appear on the map you can insert an additional line per port into the file latlong txt which is in the POLTIPS 3 directory Use one of the existing lines in the file to line up the data as shown in the following example Aberdaron 52 48 N 04 43 W 41 Aberdeen 57 09 N 02 05 W L 1 Aberdovey 52 32 N 04 03 W 41 Aberporth 52 08 N 04 33 W 4 2 In the above example Aberdaron will be plotted on the map at 52 48 North 4 43 West The first number after the position indicates at what zoom level the port should be displayed 1 always displayed 2 3 4 means that it is only displayed as you zoom in further The last number on the line indicates where the text is written relative to the location marker see the example below This is used to prevent the names of ports in close proximity overlapping Uses pos
51. ions called the Lowest Astronomical Tide or LAT therefore making all the predicted tide level values positive However this is not always the case and for some ports the surveying authority has set chart datum above LAT Chart Datum does not conform to any uniform tidal level as it is based on the tidal range at the location Therefore it is not a suitable datum for comparing levels at more than one location Ordnance Datum Ordnance datum is sometimes referred to as land survey datum andisa horizontal plane It is used when the absolute heights along a stretch of coastline need to be compared The datum used for the British mainland and some of the closer offshore islands is called Ordnance Datum Newlyn as it is based on the average value of mean sea level at Newlyn for the six year period from 1915 to 1921 Due to the subseguent rise in mean sea level this datum isnow about 0 2m below mean sea level at Newlyn For locations not on the British mainland other horizontal datums exist Ordnance Datum Belfast ODB for Northern Ireland Ordnance Datum Dublin ODD for the Republic of Ireland and Ordnance Datum local ODL for more remote locations European locations have their own land levelling datum Datums in POLTIPS 3 When making a prediction in POLTIPS 3 the default datum is always Chart Datum unless a special datum is specified for the port usually given in the port name For most locations you can switch between C
52. is probably the most common question we get asked and it could be something to do with the fact that many reference books explain it incorrectly Most people think the moon rotates round the earth In reality the earth and the moon rotate about a common centre just inside the earth s surface indicated by the light blue dot on the diagram At this position the two forces acting gravity towards the moon and a rotational force away from the moon are perfectly in balance They have to be otherwise the earth and moon would not stay in this orbit Indicates centre of rotation for the EartirWioon system The rotational force Gravity is stronger is stronger then than the rotational gravity force Page 67 The tide generating force is the difference between these two forces not just gravity as most people think On the surface of the earth nearest the moon gravity is greater than the rotational force and so there is a net force towards the moon causing a bulge towards the moon On the opposite side of the earth gravity is less as it is further from the moon so the rotational force is dominant Hence there is a net force away from the moon It is this that creates the second bulge away from the moon note that even this explanation is simplified for the purposes of this FAQ 5 Why are the tides not the same all round the coast of Britain You might expect that as Britain passes under the bulge of water time of high w
53. ition 3 Postion SB Sion 2 osition osition PA Position 5 Position 1 Uses position 5 Uses position 1 Position 6 Position 8 ma osition Uses position 7 To be able to click on a port and have it automatically selected in the input dialog box the port name in the latlong txt file and the index dat file must be the same although it is not case sensitive Handling Different Time Zones UT GMT or Local Time If you require the tidal data to be computed in a time zone other than UT GMT there are two ways you can achieve this e The harmonic constants have the phase values in UT GMT and the data is time shifted by POLTIPS 3 to output the information in the correct time zone along with the appropriate labels on the output e The harmonic constants are derived with the phase values already set such that the data is directly computed in the correct time zone This Page 54 scenario is most likely if the original tide gauge data that was analysed was also in local time zone POLTIPS 3 must know which of these two methods is being used For the first method the data is time shifted into the correct time zone and the appropriate time zone label shown on all the outputs For the second method no time shift needs to be applied since the harmonic constants already have this included in the phase angles Therefore POLTIPS only needs to know the time zone so that it can correctly label the output Specifying on non UT GMT Time Zo
54. ked Guestions about Tides The Applications Group at the Proudman Oceanographic Laboratory are often contacted by people wanting to know about tides For this reason we compiled a Frequently Asked Questions page for the NOC web site This is included below 1 What is a tide This is not as obvious as it may sound it is not just the rise and fall of the water in our seas and oceans tides are only one of the contributing factors in this rise and fall A tide is the regular and predictable movement of water caused by astronomical phenomena the way the earth moon and sun move in relation to each other and the force of gravity These are the values that you can see in tide tables Movement of water caused by meteorological effects for example winds and atmospheric pressure changes is called a surge These are not easily predictable and require powerful computers and sophisticated software to predict just 36 hours in advance These are the reasons why tide table predictions do not always agree with observations The NOC develops the storm surge models for flood forecasting that have been run at the Met Office since 1978 A large positive storm surge can add a few metres to the predicted water level There is also wave movement which is purely wind generated and impossible to predict accurately Therefore statistical values are used such as significant wave height which is the average of the highest one third of waves 2 How far ahead c
55. l POLTIPS 3 o Pleasereadbeforeinstallation 11 HOW to start POLTIPS 23 seren enel elek eek kal mesi sala kek babe 11 TroubleshootiMg sei s iasvchsss accesisscavsdcnsahdavassicates cassasuceancasesdancbcdacandeddoassendsasensnes 11 Portswithcomplextidalpattems 12 The POLTIPS 3 WINDOW asama cox sctevesseesddesstcevesceaccuiedesesarsstssasevensscaadeueeses ansess 13 Using POLTIPS 3 sve 144011 na Hazne ardea a EEEE E ERAN 15 Settingtheparametersfortheprediction nn 15 EISE VIEW e ilan se n lama sne d n so sass dasaueecaaceiasscdbeaectsteedsauniees Gi 16 MIDS ta bleM eM sirali aneia a gine basili dek ea adsdeeidantvavevacessacedceay 17 EgualintervalPredictions 18 Outputprecisionandunits 0 1 20 DATUMS i siye eaten sha illa alani leli aaa iaaa aaia naad aia Seaain ia ianei 20 FormattingthelistVieW 21 Savingtidaldatatodiskortheclipboard 22 Savihig a file todiskK sess saman vakada dama a aa de Using th Clipboard ss shccveversecicosccowncnsdesvadeensens cavensoestasncnss esl shunstnaceccesvacentvents Graphing the tidenes enee a a a ETE ENEE RA Formatting the graph view SwitchingbetweenthedifferentvieWs 25 Locations with complextidalcha
56. ld use local tide tables available from tackle shops when possible Cromer Lowestoft and Aldeburgh are fairly close to each other on the East Anglian coast However high tide is hours apart at these places This is precisely the opposite to Southend and Herne Bay which face each other across the mouth of the Thames Their tides differ by only a few minutes Without detailed geographical information it is impossible to predict these differences so stay with local tide tables Geography also affects the tidal range Looking at tide tables for all of Britain it s clear that the height of the tide varies around the country For example the spring tidal range at Avonmouth is 12 2m 40ft while at Lowestoft it s only 1 9m 6ft Weather which can have a profound effect on the tide is impossible to predict when calculating tide tables Strong winds and abnormal atmospheric pressure are two of the main causes of altered tides For example a strong wind blowing on to land has the effect of piling up the water giving a higher than predicted tide Page 60 Page 61 A History of Tidal Prediction It has long been known that there is a relationship between the movement of water in our seas and oceans and the position of the sun and moon Pytheas of Marseilles in the 5 Century BC was the first credited with linking the tides to the position of the moon Pliny the Elder AD 23 79 noted that for twice daily tides the maximum tidal ranges occ
57. ll the results on to third party publishers without written permission from NOC See also the restrictions on Internet publishing below Users will also be able to use the custom tide table layout and use their own harmonic constants subject to the same 2 or 3 year licence The UserData version of POLTIPS 3 is provided without any data sets It is for use by users who want to compute predictions using their own harmonic constants and is usually sold with a 10 year licence Publishing tidal prediction on the Internet Only users of the Custom Publishers and UserData version of POLTIPS 3 can publish the results on the Internet This is limited to one month in advance of the current date Hardware Reguirements The minimum requirements for POLTIPS 3 is a PC running Windows XP Vista or Windows 7 with about 10MB of free hard disk space Prediction Methods Harmonic constants are used for computing predictions for standard ports with time and height differences used for the secondary ports Some standard ports have additional tidal terms called Shallow Water Corrections Harmonic Constants and Standard Ports A set of harmonic constants exists for most of the main ports around the coast These are called standard ports and POLTIPS 3 can compute equal interval predictions as well as high and low waters Sets of harmonic constants usually exist only for locations where there has been a tide gauge Page 9 and a suitable period of observe
58. lumns Step 1 of 3 of the text to columns wizard appears 3 Select Fixed Width for the original data type and click the next button Convert Text to Colum rd Step 1 of 3 2 1 The Text Wizard has determined that your data is Fixed Width Tf this is correct choose Next or choose the Data Type that best describes your data iginal data type Choose the file type that best describes your data Delimited Characters such as commas or tabs separate each field Fixed width Fields are aligned in columns with spaces between each field Preview of selected data ERT BRIDGE TZ GMT only 03 08 2001 01 39 5 70 03 08 2001 08 36 0 39 03 08 2001 13 56 5 73 03 08 2001 21 11 0 29 Units METRES Datum Chart D Al 4 Excel will suggest some columns by putting the date and time in one and the heights in a second one Accept these by clicking next This screen lets you set field widths column breaks Lines with arrows signify a column break To CREATE a break line click at the desired position To DELETE a break line double click on the line To MOVE a break line click and drag it ata preview L Mee P ed 0 ALBERT BRIDGE TZ GMT only Units METRES Datum Chart Dat aj 03 08 2001 01 39 5 03 08 2001 08 36 0 03 08 2001 13 56 5 03 08 2001 21 11 0 5 Clickfinish to accept the default settings for each column Page 56 6 You will
59. n certain days the fourth tide actually gets pushed across into the next day The diagrams below show a typical tidal curve for three places round the UK coast Lowestoft Portland m HH TTT In some parts of the world there is only one high and one low water each day diurnal for example in Karumba Australia In other places it varies between semi diurnal and diurnal as in Musay id in the Arabian Gulf 8 What are spring tides and neap tides When the earth moon and sun are in line during new and full moon the bulges of water caused by the moon and sun occur in the same place on the earth s surface The lunar tide and the solar tide are reinforcing each other which leads to higher than average high tides and lower than average low tides These are called spring tides When the earth moon and sun form a right angle at 90 the high water caused by the lunar tide coincides with the low water of the solar tide This produces lower than average high waters and higher than average low waters which are called neap tides They occur approximately 7 days after spring tides 9 Why are they called spring and neap tides Page 69 Neap means low so that is an easy one Spring tides can be confusing because they have nothing to do with the season It is not exactly known where the word spring comes from in this context but there are two possible origins One possible source is a Scandinavian word meaning to leap up Anot
60. ne To specify a non UT GMT time zone you should include a dummy harmonic constant in the usercon dat file This should have an amplitude value which gives the time shift in hours a phase value of 0 000 and a harmonic constant number of either 1 or 2 The time zone is specified in reverse as is the norm on tide tables Example the port of Calais in France is 1 hour ahead of UT GMT therefore the amplitude for the dummy time zone harmonic is set to 1 0 as it would normally be displayed as Time Zone 0100 on the tide table If the harmonic constants are already adjusted to this local time zone specify a value of 2 for the harmonic constant number However if the harmonic constants are all in UT GMT and you require POLTIPS 3 to adjust the output data into the local time zone put 1 as the harmonic constant number Remember to increase the harmonic constant count by 1 for the additional constant 115 9 PORT OF CALAIS FRANCE 4 09 0 000 XXX 1 0 O i 2 51 10 2 31 0 77 62 4 36 Page 55 Using the data in Microsoft Excel 97 If you paste the data into Microsoft Excel all the information will be placed in the first column of the spreadsheet To make the data more useable you really need the date and time in one column and the levels in another column To do this follow these steps 1 Select column A by clicking on the letter at the top of the column 2 From the Data menu select Text to Co
61. ome locations have a tidal regime that is very complex 3 00 215 25 225 20 175 16 9 2011 17 9 2011 Below is a graph for the location Islay Port Ellen 1 00 075 050 025 0 00 6 9 2011 71 9 2011 8 92011 9 9 2011 Even an experienced tidal publisher would have difficulty identifying which tides should be included in a tide table On the 6 9 2011 look how high the second high water is Page 28 On the 7 9 2011 where is the second low water on that day On the 8 9 2011 there are three possible candidates for the morning low water Producing a tide table for Islay is near impossible and different software would pick different principle tides Even manual selection of the tides could lead to a different tide table depending on who picked them For this reason POLTIPS treats complex tidal locations a little differently When a tidal prediction is made the software first looks for days when there are five tides If it finds any the software can produce a tide table as normal but will reduce the line spacing to fit in the extra tide Although a rare occurrence it most often happens on BST adjusted tide tables when the clocks go back an hour BST returns to GMT On this day there are 25 hours and therefore a fifth tide is more likely If any day is found to have six or more turning points then you are given two options i POLTIPS can try to POLTIPS3 identify the main turning points and One or m
62. onstants 51 Belle m YEL 51 Accessing the sample ports includedwithPOLTIPS 3 53 LICENCE RESEMICTIONS dacs sesez ses samimi kaale ka kayi enine aetate aaaea s se esad 53 Showingyourporttonthemap 54 Handling Different Time Zones UT GMTorlocalTime 54 Specifyingonnon UT GMTTimeZone eeeee 55 UsingthedatainMicrosoftExcel 97 56 TTimezand Mid Esiste endan Spiker sanada alada as asama dual al aselsan i 58 AkHistoryofTidalPrediction 62 FreguentiyAskedOuestionsaboutTlides 66 e ka Kl T YE e e A Ye e eyy e Vee 74 TableofStandardHarmonicConstants 78 Page 4 Warranty and Liability 1 If the licence disk or CD ROM is defective NOC will replace it at no charge provided the defective item is returned within thirty 30 days from the date of despatch from the National Oceanography Centre NOC 2 NOC will refund the purchasing price provided all items CD ROM licence disk and user manual is returned within thirty 30 days from the date of despatch from NOC and provided that all seals remain intact No refund will be made if the seal has been broken on any items 3 The latest version of POLTIPS 3 will be avail
63. ore days has greater than 5 tides Would you like pa POLTIPS 3 to try and remove these extra tides remove the extra ones or ii you can m ee a oe elect to keep all turning points ME i E although tide table formats will only e i lar my ra show the first five on any day anda e warning will be given by the software toremind you If you opt to remove the additional tides then it is vital that you check the data The procedure for doing this is outlined below Checking the Data When you opt to remove the tides you should view the data as a graph Output gt Graph View The plot shows the tides that POLTIPS has identified as being the principle turning points blue dots and the turning points it has selected to remove red dots You can toggle the red dots on off by pressing X on the keyboard Page 29 B S SBD lelles 9 High and Low Waters for WEYMOUTH Time Zone GMT only Predictions to Chart Datum m 4 9 2011 11 9 2011 18 9 2011 25 9 2011 The plot on the previous page shows a month of data for Weymouth To inspect the data more closely zoom in onto a period to show a couple of days at atime You will see that POLTIPS does not always pick the lowest low water and highest high waters when there are multiple tides In most cases it will select the first low or first high water as the principle one as this will lead to better consistency from one tidal cycle to the next lalaj H
64. ors that can influence the tides see Time and Tide on page 58 To change the precision of the output select Output Precision You also have the option of switching the units used for the sea level between metres default or feet Select Output Units and select the unit you require Note if you select feet for the units the value is a decimal value and not feet and inches e g 4 5 means 4 4 6 and not 4 5 Datums What is a Datum When measuring the height of something you must specify what that height is measured relative to For example if you hold a ball out in front of you over a desk the height of the ball is say 70cm above the desk However if someone comes and takes the desk away you could say the height of the ball is 145cm above the floor You have two different heights even though you have not moved your arm What has happened is that the datum has changed In the first case the datum was the desk and in the second the datum was the floor Likewise tide heights must be measured to a specified datum the two most common being Chart Datum and Ordnance Datum although some ports use a datum specific to that location for example a dock sill These are called special datums Chart Datum This is the most common datum used on tide tables and is defined as the datum of soundings on Admiralty Charts It is usually set to correspond to the Page 20 lowest level to which a tide can fall under normal condit
65. ound 1910 however the most complete algebraic expansions were completed by Dr Arthur Doodson pictured right in 1921 then secretary of the Liverpool Tidal Institute and from 1946 to 1960 Director at Bidston In 1924 the Liverpool Tidal Institute under the directorship of Professor Proudman at Liverpool University relocated to Bidston Observatory and the first tide predicting machine was installed This machine could be programmed with the harmonic constants for any location and used to predict the tides for any date and time A yearly tide table took nearly a week to produce Five years later the Liverpool Observatory of the Mersey Docks and Harbour Board and the Tidal Institute of the University of Liverpool amalgamated becoming the Liverpool Observatory and Tidal Institute Dr Doodson now associate director continued his ground breaking research into new methods for the analysis of tides Two tide predicting machines were now in use the only two in the British Empire and the tidal expertise of the institute received worldwide acclaim During the Second World War valuable work was carried out at the observatory The staff worked seven days a week from early morning to late at night analysing and predicting tides towards the war effort Tidal predictions were swiftly predicted for the seas around Burma France and Page 63 Holland During these years one of the tide predicting machines was placed in a secret underg
66. racteristics 27 Checking the Data sis sesime rassal daa ai anka mn geadescandazeasedaseavocbeaten 29 TidalStatistiCS saanen sesde Maas asabe sue k asoni gey onlayn elsa akya 33 Using the MA Diesre Sek ne maal mekan meleri asiye kase Baya 35 Selectingaportforprediction 36 Showingthelocationofaportonthemap 36 Sunrise SE S NSEttiMES sisisesar dasetida sas saa sardalya bakaya sie spin Wasa aka ds a ER K a 37 Fixedformattidetables 39 Additional fixed format Vssisiicsccrs cacccsvecsseasccvecesiavesses ivvvesusssiesndevassadceadsovevesae 39 Additional fixed format 2 vss csccscxs maniler dsl seren sakala les asia aside sasi 40 Additionalfixedformat3 41 Custom tide table format analdan sazdan a la az 43 RM tl ay eee aaa aya ran imali ea akla saa aa aaa sasi e ats 43 Appearance ta Depreni e ie sediklari ire E EA EAEE asl sinde 44 Advanced tab sess same san kaka anisina Sayan anakara Salan 46 Savingyourtidetablesetting3 47 VerticalSpacingoftheData 48 BatchModeOperation e 49 PBF File Fomati maker elmada a yalmaya dp bileni la am al emaye da a esi ba kesik 49 Usingyourownharmonicconstants 51 AboutHarmonicC
67. raph button on the toolbar Pel The picture below shows how one month of high and low waters might look When you view the graph of a high and low water prediction blue diamonds indicate the time horizontal axis and height vertical axis of the data In the picture below you can clearly see the spring neap tidal cycle o Ne 3 5 x File Edit View Input Output Misc Help D S amp almliilm Hlal 2 High and Low Waters for AVONMOUTH Time Zone GMT only 16 0 140 13 0 12 0 11 0 10 0 9 0 8 0 70 60 5 0 40 3 0 20 10 beest Predictions to Chart Datum 0 0 6 1 2002 13 1 2002 20 1 2002 27 1 2002 Ready Z You can zoom in to any section on the graph by holding down the left mouse button and dragging from left to right across the graph You will see the area you are selecting change colour and when you release the mouse button the selected area will be scaled to fill the window You can also use the buttons on the toolbar QJ to zoom in and out Page 23 You can scroll left and right within the limits of the prediction using the left and right arrows on the keyboard or the toolbar If you view the graph of an egual interval prediction you get a continuous line showing the shape of the tide To get an accurate graph it is advisable to use an interval of 15 minutes or less for the prediction Below shows how a 5 minut
68. round room in the Observatory grounds for security reasons Photographic facilities were obtained so that further copies of the predictions could be quickly provided in the event of their loss at sea In 1946 Dr Doodson took over as Director at Bidston and the Tide Prediction Service expanded It was helped by the construction of a large 42 constituent Doodson L g predicting machine in 1949 This machine is still in working order at Bidston and can still predict the tide to an incredible accuracy In 1961 shortly after the retirement of Dr Doodson the Liverpool Observatory and Tidal Institute was renamed The University of Liverpool Tidal Institute and Observatory In 1969 the Institute became a component body of the Natural Environment Research Council and was renamed the Institute of Coastal Oceanography and Tides ICOT It was around this time that an ambitious marine research programme was embarked upon with a significant increase in staff 1970 saw the installation of the institute s first mainframe computer an IBM 1130 This speeded up the computation of tide tables immensely a yearly table now taking less than an hour to compute The reduction of human intervention also meant that errors were less frequent so less time was spent checking the results for typing mistakes In 1977 the institute was renamed yet again to the Proudman Oceanographic Laboratory in honour of Professor Proudman It continued to dev
69. rth are in line That s when lunar and solar tides line up and reinforce each other making a bigger total tide Neap tides occur when the moon is in the first or third quarter when the sun earth and moon form a right angle The lunar high tide coincides with the solar low tide and they partly cancel out giving a small total tide Because of the regular motion of the sun moon and earth spring tides occur roughly 36 to 48 hours after the full or new moons and for any given location always at roughly the same time of day For example at Liverpool the spring tides are generally around midnight and midday Not all spring tides are the same size Springs nearest the equinoxes 21 March and 21 September when day and night are of equal length all over the world are slightly bigger The explanation for this is very complex and won t be given here Worldly Effects Back on earth tides are affected by more mundane things such as weather and the shape of the coastline In the upper reaches of estuaries the riverbed and shape of the estuary can distort the tidal pattern producing long flood times and short ebb times Though the time from high tide to high tide is the same as usual roughly 12 hours 25 minutes low tide is not half way between Page 59 them At some places the flood tide rises quickly after a period of low water lasting maybe four or five hours This kind of geographical effect is very important and because of it you shou
70. s means that on the near side the moon tends to pull anything that s free to move towards it In the same way on the far side there isn t quite enough gravitational pull so that anything that s free to move tends to fly off away from the moon Of course though land isn t free to move the oceans are So on the near side they are pulled into a bulge towards the moon and on the far side they pile up into a bulge away from the moon Page 58 As the earth spins different parts of the world move under the two bulges of high water and experience high tides giving the familiar two tides a day semi diurnal tides around Britain In some parts of the world local effects can mean only one tide a day diurnal tides for example in the South China Sea and parts of North Australia or even no tide at all Between the two bulges are two troughs of low water producing two low tides a day The sun also creates a very similar though smaller effect the solar tide and it is the interaction of the lunar and solar tides that causes spring and neap tides Springs and Neaps Tides change in height with low water level and high water level varying throughout the month The tides build up to a maximum and fall to a minimum twice a month The tides with the biggest difference between high and low water are called springs and those with the smallest are called neaps Spring tides happen just after every full and new moon when the sun moon and ea
71. s to compute high and low waters sometimes known as turning points however you can select egual interval predictions and specify the time interval in minutes default is 60 minutes You can also opt to just have the high waters the low waters or general tidal statistics for the location see page 32 Finally select if you want times adjusted for British Summer Time box ticked or to leave all times in GMT UT unticked And that s it just click compute and the results will be displayed in the window If you selected a long duration or you have a slower computer you will see a progress indicator in the bottom left corner of the window and the calculation may take a few seconds List view New Prediction POLTIPS 3 DAR Fie Edit View Input Output Misc Help Page 1 of high low water prediction for LIVERPOOL GLADSTONE DOCK ime Zone GMT only Datum Chart Datum vel m m 46 02 02 02 02 PNNNNNNNNNNNNNNNNN o N When you make a prediction it is always initially displayed in what is called the list view see picture This gives one high water or low water per line As high waters and low waters always alternate unless you selected high waters only or low waters only in the dialog box it should be obvious which is a high water and which is a low water Page 16 To scroll up and down through the prediction use either the page up and down keys on your keyboard the up and
72. ss hatching is to indicate the largest sguare area that can be displayed in the window This allows consistency between the screen and printouts as the non shaded area is the only part guaranteed to appear on both It also remains consistent as the window is resized Selecting a port for prediction To use the map to select a port zoom into the area so that the port name is visible and click on the small diamond next to the port name with the right mouse button The Tidal Predictions dialog box will appear with the port name already selected Showing the location of a port on the map If you have the Tidal Prediction dialog box on screen and want to locate where a particular port is select the port from the list and click on the Show on Map button The dialog will disappear and switch to the map view with the selected port centred in the window and the zoom level set appropriately to show the surrounding ports Page 36 Sunrise amp sunset times Year jon S As POLTIPS is used by some almanac Faran erdeen publishers it also has the option to Aberdovey A erp generate tables of sunrise and sunset Aberystwyth o Cnel eburg times either by selecting the port or Aldemey Braye specifying the exact location in latitude and longitude and height above sea level To bring up the dialog box select Input Sunrise and Location sunset by port to select one of the coastal degrees minutes loc
73. stom Tide Table layout files use the file extension ctt Note that any custom datum statement or custom port name is not saved as part of the tide table layout If the layout was applied to a prediction for a different port this information would be wrong Vertical Spacing of the Data The vertical spacing of the data is worked out automatically based on the number of data columns per month You should ensure that you select a font size that is appropriate to the spacing On rare occasions it is possible for there to be five tides on one day When this happens POLTIPS will automatically reduce the spacing slightly If you select a font size that leave very little space between the tides then they may overlap when POLTIPS needs to reduce the spacing to allow for an extra tide In the example below the data on the right shows an extract from a tide table computed with British Summer Time On the 28 the clocks went back therefore the 00 12 was in BST and the others on that day in GMT This lead to an extra tide on this day which does not appear in the example on the left where the whole tide table was produced in GMT Pe TUS oa TUTA T TUS oa TOTS UT T 5 5 38 2312 5 66 2 5 5 38 2 E A 0517 1 00 0 7 124 0012 5 66 0 7 542 28 1124 5 58 13 1 7 542 28 0517 1 00 13 1 1 079 Su 1751 074 Tu 1 1 0 79 Su 1124 558 Tu 1 6 569 2351 570 2 6 5 69 1751 0 74 2 7 0 99 0554 0 88 0 oe 7 0 99 0554 0 88 0 4 5 69 29 1203 5 65 14
74. t of water caused by meteorological effect e g wind atmospheric pressure changes These are not easily predicted requiring accurate weather forecasts and complex computer models of the seas and oceans Tide tables do not included predictions of the surge and explains why they may differ from what is observed See question 1 of the Frequently Asked Questions page Error Bookmark not defined Tidal Analysis the process of extracting the amplitude and phase of each harmonic constituent from a period of tidal observations from a tide gauge This creates a unique set of harmonic constants for that location Tidal Range the difference in height between high water and an adjacent low water As this is not constant it is usually quoted as one of the following e mean tidal range the average difference between high water and adjacent low water e mean spring range the average difference between Mean High Water Springs and Mean Low Water Springs e mean neap range the average difference between the Mean High Water Neaps and Mean Low Water Neaps Page 76 Tide Type specifies whether the tide is semidiurnal diurnal or mixed The eguation below is used to calculate a value that is used to decide this Value Tide type Value O K 0 0 to 0 25 Semidiurnal M S 0 25 to 1 5 Mixed mainly semidiurnal o 1 5 to 3 Mixed mainly diurnal greater than 3 Diurnal Time Zones Tidal predictions are
75. the name of the Ordnance Datum used e g ODN ODL ODB ODD As chart datum is normally below Ordnance Datum this value is usually negative This is followed by one line per harmonic constant i e if you specified there were 10 harmonic constants there should be 10 extra lines Each line has 3 values separated by one or more spaces The three values required for each harmonic constant are the amplitude in metres the phase lag in degrees for information on how time zone relates to the phase lag see the section below and the harmonic constant number see table of harmonic constants on page 78 If you have a customised licence or a UserData licence then there will be a sample USERCON DAT file included giving three examples the first two matching those shown above The first one contains just a single M2 constant so any prediction made will look like a basic sine wave with a period of 12 hours 25 minutes The second example includes M2 and S2 the principal lunar and solar constituents and a prediction made with this will show a simple spring neap variation The final example is of a real port not disclosed as it is for sample purposes only and uses old data and contains 17 harmonic constants Accessing the sample ports included with POLTIPS 3 If you have a UserData licence the entries for these three sample ports will already be set up in the INDEX DAT file If you have a customised POLTIPS 3 licence these ports are not listed
76. the toolbar or press J S Page 33 The information calculated is Position the latitude and longitude of the port if available Port details usually states whether the port is a standard port with harmonic constants or a secondary port based on time and height differences with the reference standard port Datum of Predictions The height of Ordnance Datum relative to Chart Datum and a description of how the Ordnance Datum is defined Highest Astronomical Tide HAT the highest level the tide is likely to reach under normal meteorological conditions and the date this occurs between 1997 and 2015 see glossary Lowest Astronomical Tide LAT the lowest level the tide is likely to reach under normal meteorological conditions and the date this occurs between 1997 and 2015 see glossary Maximum Tidal Range possible the largest difference that occurs between one high water and its adjacent low water during the period 1997 to 2015 Mean High Low Water Springs Neaps MHWS MHWN MLWN MLWS see glossary Tide Type gives the value which indicates whether the tide is semidiurnal diurnal or mixed see glossary Shallow Water Influence an indication of how much shallow water effects influence the overall tide Values over 0 2 indicate a port that shows unusual tides especially during neap tides Statistics for the Selected Period Page 34 Highest Tide in period the highest level the tide re
77. tive text optional however 80 spaces must be typed if no text is supplied This is displayed in the input dialog box when a port is selected 123 to end of line long port name used by default on the hourly height tide table and optionally on the custom high and low waters tide table format max 72 characters Normally only standard ports have a long name although one could be added for any port in the index file As the spacing of the information must be precise in use an existing entry to line up the different pieces SAMPLE M2 ONLY of information when inserting your own entry into 3 000 the index file IN 2 000 0 0 31 20 USERCON DAT SAMPLE M2 AND S2 3 000 lili 1 000 ODN This file is used to store all your own sets of 2 000 0 0 31 harmonic constants that you will want to use in 1 000 0 0 36 POLTIPS 3 not the standard licence Each port has a minimum of 4 lines of header information and then a list of the harmonic constants one per line as shown in the example Page 52 The first line has two values that indicate how many standard harmonics and how many shallow water constants are used for the port the latter value will nearly always be zero The second line has the port name which in the example is SAMPLE M2 ONLY The third line contains the datum shift to get from mean sea level to chart datum sometimes called Zo The fourth line is the height of Chart Datum relative to Ordnance Datum and
78. ton to accept the changes and close the dialog box Once you have clicked Apply you can no longer select cancel you will need to change the settings back manually Font tab High and Low Water Custom Tide Table Format x This tab allows you to select the font size weight and italic properties for each of the 6 parts of the tide table All the fonts installed on your system should be listed in the drop down list under typeface name 3 38 105 D a izi a PUBL ele Bll ela lek al 8 Title refers to the top line of the tide table used for the port name Page 43 Subtitle is the line directly below the title used to display the time zone latitude longitude and the year Month is the font settings for the month headings Date is the settings for the date value Data refers to the font used for the main tidal data as well as the time and units headings and the day of the week Footer is used for the datum statement and the footer text that appears at the bottom of the tide table In POLTIPS 3 the font size is not specified in the conventional unit of points but in its own units to allow greater precision in specifying the size To convert from point size into POLTIPS 3 font size multiply by approximately 12 Point Size POLTIPS 3 Size Point Size POLTIPS 3 Size 20 pt 240 11pt 132 16 pt 192 10 pt 120 14 pt 168 9 pt 108 12 pt 144 8 pt 96 T
79. ul and easy to use set of features there may be times when you need to export the data into another Windows application POLTIPS 3 gives you two ways to do this e save the list view to a text file on your hard disk e copy and paste via the clipboard Saving a file to disk Compute the tides as normal and ensure list view is selected Make any changes to the layout using the Format List View dialog then select either File Save as Text File click on the save button on the toolbar or press J S Enter the filename and click the save button to save the prediction to disk This can now be loaded into any Windows application that will read in a plain ASCII text file e g notepad Word Excel Using the Clipboard A quicker way of getting data into another application is to use the Windows clipboard Make your prediction as normal then select Edit amp Copy click the copy button on the toolbar or type 4C Now simply switch to the application you want to put the tidal data into and select paste from the edit menu of that application Provided the program supports text input the data should appear in the application Page 22 Graphing the tide In addition to the list view and the tide table view POLTIPS 3 can display the tide as a graph How this graph looks depends on whether you display a high and low water prediction or an equal interval prediction To bring up the graph of the tide select Output Graph or click on the g
80. ur just after the full and new moon and how in March and September they were likely to be even larger still Strabo c54 BC to AD 24 also noticed that the tidal range in the Persian Gulf was greatest when the moon is furthest from the plane of the equator and are small and irregular when the moon passes through the equatorial plane Of course not all facts about the tide were scientifically correct Aristotle is credited with the law that no animal can die unless the tide is going out This legend persisted for a long time and even as recently as 1595 Parish Registers in Hartlepool recorded the phase of the tide along with the date and time of each death By the mid 17 century many theories were being proposed to explain the movements of the tide Galileo 1564 1642 stated that tides were caused by the motion of the Earth around the Sun and its own rotation on its axis inducing motions in the sea which were modified by the shape of the sea bed This is closer to what actually happens than Descartes 1596 1650 theory that space is filled with an invisible matter called Ether which is compressed as the moon passed overhead and pushes down on the oceans However Kepler 1571 1630 was the first to state that the Moon exerted a gravitational attraction on the water In the years that followed and as the laws of planetary motion and gravitation became accepted Kepler s idea of the tides became the most plausible It wasn t until Isaac Ne
81. wton 1642 1727 and his law of gravitational attraction that everything fell into place He was the first to correctly explain the spring neap cycle and why equinoctial tides were larger than those at other times of the year Now that tides were fully understood scientists started to look for methods to accurately predict them for any date and time future and past Various methods have been devised for this and all start with having a good series of observed sea levels which are analysed to identify repeating patterns in the tide Page 62 In 1832 Sir John Lubbock developed a method of analysis and prediction based on relating the time and height of high and low water to the time of lunar transit with corrections made for lunar and solar declination and distance However the method generally considered to be the most accurate for most but not all locations is called Harmonic Analysis and Prediction The basis for harmonic analysis is that the tide can be represented by a finite number of simple harmonic terms each one a simple mathematical sine wave Each constituent either individually or in pairs corresponds to one of the astronomical phenomena to affect the tide Harmonic prediction involves simply calculating these harmonic waves for any point in time and adding the results together to get the overall tide Early development of Harmonic Analysis was carried out by Laplace Lord Kelvin and George Darwin ar
82. y than the moon Hence the tidal force is approximately 0 000054 times that of the moon That equates to a movement in sea level of less that a quarter of a millimetre one hundredth of an inch The next most significant planet is Jupiter where the tidal force is 10 times less again So as you can see the effect of the planets on the tide can safely be ignored Page 70 Even if all the planets line up such that their effects are combined the additional force would be minuscule On the 3rd May 2000 Mercury Venus Mars Jupiter and Saturn lined up with the sun and moon At the time a rumour circulated that the collective gravitational pull would initiate earthguakes tidal waves and volcanic eruptions something which of course never happened 14 How can tide tables be produced so accurately There are many different steps involved in obtaining the final numbers that go into a tide table Before a tidal prediction can be made for a port along seguence of tidal observations for that port are needed called a time series This time series will include all the astronomical effects and local coastline depth effects which make up the tide as well as the weather induced effects called the surge see guestion 1 As shown in guestions 6 and 8 there are certain freguencies that are known to occur in the tide Some of these are listed below e 12 hours 12 00 00 repeated pattern cycle due to the gravity of the sun e 12 25 14 164 cycle du

POLTIPS 3 - National Oceanography Centre

Contents

Download Pdf Manuals

Related Search

Related Contents