Garmin GPSCOM 190 Two-Way Radio User Manual
Contents
1. World Health Survey GPS Field guide WHO 2002 09 25 02 GPS field guide 8 19 A9 P9 CONTENTS CHAPTER 1 INTRODUCTION TO GPS lb W batis GPS entel nsi eE E EE inner 2 L2 HOW AOC GPS WOEK Loveren teint 3 LS Source or GPS Signal Grr Sorreran e NE ete vetten eme bend 7 CHAPTER 2 WHY USING GPS IN THE CONTEXT OF THE WHO WHS CHAPTER 3 PRESENTATION OF THE GARMIN ETREX GPS UNIT 3 1 Overview ot thee TTEK UNil 00524 ssenacaeeisa gee eeensss OEE a dear 10 5 2 STOM OE HCS FLS UNI oscar brede oa 13 3 2 1 Installation of the batteries oaeen 13 3 22 Tieeltex operduns Syste oseere anra E ENE T 13 Iek LIC CITA Pad O an one a TA E OAE 14 3 2 3 1 The NORMAL SKYVIEW SATELLITE page 14 The DISPLAY Paces nanne erdee netten de 16 The ADVANCED SKY VIEW SATELLITE page 17 Deo he MENU DALE eben enen attended 17 The MARK WAYPOINT option page enen 19 The SETUP OplOn paces in onse anmeee ne kheden EOL end 19 The UNITS Seip BAGS ennen inteken EEEN 20 The SYSTEM Sep paces reservaat ate etsen aha 20 CHAPTER 4 TROUBLESHOOTING A AC rex dOESM EEN neea a A O E ES 21 4 2 The message READY TO NAVIGATE doesn t appears on the screen 21 4 3 The message TROUBLE TRACKING SATELLITES ARE YOU INDOOR NOW appears on the screen oon 21 4 4 Tam not getting an accuracy higher better than 20 meters 22 4 5 eTrex does not display the desired units when making the accuracy or coordinates TEACING eserit2. know which of the two points is the correct one In any case a configuration with 4 satellites is better in order to increase the accuracy and or reduce the sources of error 09 25 02 GPS field guide 8 19 A9 P9 1 3 Sources of GPS signal errors Even if today s GPS receivers are extremely accurate certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers If most of the sources of error are unavoidable it 1s important for the user to be aware of the ones that he can influence and be prepared to take steps to reduce their impact The greatest source of error is connected to the position of the satellite in the sky when taking the measurement The spread of the satellites in the sky is called the Positional Dilution of Precision PDOP A good PDOP 1s obtained when the satellites are located at wide angles relative to each other Figure 6 a In the contrary a poor PDOP result from satellites being located in a line or in a tight grouping Figure 6 b poot PDOP Figure 6 a Good PDOP b Poor PDOP The second source of error comes from the infrastructure buildings bridges and particular landform mountains that are located around the receiver These objects can block the reception of the signal Figure 7 causing position errors or possibly no position reading at all Figure 7 Example of good visibility a and bad visibility b of satellites due to obstacles GPS units typical
3. 02 GPS field guide 8 19 A9 P9 1 2 How does GPS work GPS satellites circle the Earth twice a day in a very precise orbit at an altitude of around 19 000 Kilometres Figure 2 This constellation allows any user to access between five and eight satellites from any point on the Earth Figure 2 The GPS Satellite network Each satellite transmits radio signal information which is tracked and used by the GPS receiver to calculate the user s exact location The satellite signal This constantly transmitted radio signal passes through clouds glass and plastic but not through most solid objects such as buildings and mountains A GPS signal contains three kinds of coded information essential for determining a position e An I D that identifies each of the 24 satellites of the network e The almanac data that contains the orbital information for all satellites in the system e The ephemeris data which contains important information about the status of the satellite healthy or unhealthy and the current date and time To determinate precise latitude and longitude position the receiver measures the travelling time of the signal between the satellites and itself and transform it into a distance 09 25 02 GPS field guide 8 19 A9 P9 The receiver 1 Calculates the distance to the first satellite he is able to catch Let s suppose that the receiver calculates a distance of 17 000 km between this first satellite and the receiver T
4. Datum and Units desired Refer to the point 7 of the Quick Reference Guide Units Setting 22 09 25 02 GPS field guide 8 19 A9 P9 4 6 eTrex does not display the local time in the SETUP page The eTrex operates on universal time or GMT Greenwich Mean Time It is not necessary to have your local time displayed Do not worry about a wrong displayed time 4 7 The geographic coordinates I get are outside the range indicated in the Country information document 1 Make sure the eTrex is configured as indicated in point 7 of the Quick Reference Guide and redo the reading correctly 2 If the eTrex is well configured check that you have a clear view of the sky 3 If this still does not work move to a better place and take a new reading 4 If the coordinates are still outside the range change the batteries 5 If all of that does not lead to a better result contact your supervisor 23 09 25 02 GPS field guide 8 19 A9 P9 GLOSSARY Accuracy How close to the real value a measurement is Backlight Selectable on off illumination that lights the display for enhanced screen at night and in low light Contrast The difference between the lightest and darkest areas on a display screen Coordinates The unique description of a geographic position using numeric characters Dilution of Precision DOP The dilution of precision DOP is an indication of the quality of the results that can be expected from a GPS poin
5. User segment The receivers of GPS signals such as your eTrex Unit 24 09 25 02 GPS field guide 8 19 A9 P9 Variance In this context correspond to the errors in magnetic compass readings caused by variance in the earth s magnetic field at different locations on the planet Waypoint Current location on the face of the Earth in terms of the specific latitude longitude coordinates BIBLIOGRAPHY LINKS This document has been created using information coming from the following publications or Web Sites Garmin International Inc 2000 Garmin eTrex personal navigator owner s manual MEASURE Evaluation 2001 Incorporing Geographic Information Into MEASURE Surveys A field Guide to GPS Data Collection Garmin Website http www garmin com Garmin GPS Guide for beginners http www garmin com manuals gps4beg pdf Eagle GPS Tutorial http www eaglegps com tutorial gps default htm Lowrance Electronics GPS Tutorial http www lowrance com Tutorials GPS gps tutorial 01 asp Mercator GPS Systems The GPS Tutor http www mercat com QUEST gpstutor htm The Aerospace Corporation http www aero org publications GPSPRIMER Trimble GPS Tutorial and Glossary http www trimble com gps work html University of Colorado http www colorado edu geography geraft notes gps gps f html Smithsonian National Air and Space Museum Washington GPS A New Constellation http www nasm s1 edu galleries gps 25
6. it must be well protected 3 The Power button Is used to turn the unit on and off as well as switch on the display backlight 4 The Page button It allows switch between pages and stop something that you have started but that you don not want to continue 5 The Up and Down buttons These buttons are used to select options on pages and menus and to adjust the display contrast 6 The Enter button This button is used to confirm data entry or menu selection and to display options from the main pages 7 The waterproof case This plastic case protects the electronic part of the device from water If the receiver falls into water make sure that the battery compartment is dry before using it again 8 The battery Compartment Represents the location of the 2 AA alkaline batteries used to make the GPS receiver work 9 External Power and Data Connector Allows the connection to an external source of power and to a computer for data download will not be used in the context of the WHS It should stay closed all the time in order to protect the connections Table 1 Description of the different eTrex components shown on Figure 9 and 10 12 09 25 02 GPS field guide 8 19 A9 P9 3 2 Utilisation of the eTrex unit This section presents the major elements that will be used in the context of the WHO WHS It introduces you to the basic features of the eTrex as well as some basic definitions of terms in a more detailed way tha
7. Figure 11 The Welcome page 13 09 25 02 GPS field guide 8 19 A9 P9 3 2 3 The Garmin eTrex Pages The eTrex operating system is composed of different pages organised in a hierarchical way starting from 4 main pages Figure 12 The NORMAL SKY VIEW SATELLITE page is one of them To Switch from one of these main page to the other you have to use the PAGE button In the context of the WHS we will only need to use two of them The NORMAL SKYVIEW SATELLITE page The MENU page FREA CY TO HAUSE ACCURACY 1dEft PAGE PAGE MOWING 17 Satellite Map Pointer Figure 12 The 4 Main pages of the Garmin eTrex GPS receiver Following 1s the description of these two pages 3 2 3 1 The NORMAL SKYVIEW SATELLITE page As mentioned earlier this main page is the first one appearing after the WELCOME page The NORMAL SKYVIEW SATELLITE page displays different information on the acquisition of satellites signals Figure 13 READY Status Message TO HAUIGATE ACCURACY EPS Location Accuracy estimated Satellites satellite Signal strength Bars Figure 13 The NORMAL SKYVIEW SATELLITE page elements 14 09 25 02 GPS field guide 8 19 A9 P9 This information concerns The Status of the device Two type of messages can appear a WAIT LOCATING SATELLITES indicating that the receiver is tracking satellite signals b READY TO NAVIGATE indicating that the receiver has found satellit
8. TER button again in order to save the change The variance field cannot be change this value is given by the GPS unit and connected with the Earth s magnetic field variation Ones all the units have been setup it is possible to keep them as default be highlighting the DEFAULTS option and pressing the ENTER button The SYSTEM setup page This page Figure 22 allows the user to fix the operation mode Normal Battery Save Demonstration It is recommended to put the device in the BATTERY SAVE mode in order to extend their life It 1s also possible to set the receiver language We recommend using the receiver in English in order to follow the instruction reported on the different documents provided It may however be useful in certain case to change the language in order to improve understanding of some options Changes can be done as in the other pages by highlightning the concerned field pressing the ENTER button to make the scroll down list appear selecting the desired language and pressing the ENTER button again to save the change STSTEM MODE HORHAL LAHGUAGE English SOFTHARE VWERSIOH 2 05 USIT HHH GARMIN COM FOR LATEST SOF THARE UPDATES Figure 22 The SYTEM page 20 09 25 02 GPS field guide 8 19 A9 P9 CHAPTER 4 TROUBLESHOOTING 4 1 eTrex does not turn on 1 Check to see if the batteries are installed correctly and if the battery terminals are clean 2 Ifthe eTrex does not turn on after
9. a n Ee ERER dees Hetagunandeneesenawnams 22 4 6 eTrex does not display the local time on the SETUP page 23 4 7 The geographic coordinates I get are outside the ranges given in the Drotocol TOM 1 2 i502dcicasvedcotadadasheseotGdadesvedeuteeneesacaoatdades ie 23 GLOSSARI peer Reenter neat nr e aa Toe CERT RMT on oe CT ea 24 BIBLIOGRA PHY 7 TINK Sccaceccsaviancosne lt tacearcaonadaaseaneasys arberensmetaihanndendt 25 09 25 02 GPS field guide 8 19 A9 P9 CHAPTER 1 INTRODUCTION TO GPS 1 1 What is GPS The Global Positioning System GPS is a system allowing to precisely identify locations on the earth s surface The GPS system has 3 parts Figure 1 e The Space segment a network of 24 satellites placed into orbit Figure 2 The first GPS satellite was launched in 1978 and a full constellation of 24 satellites was achieved in 1994 Each satellite is built to last about 10 years Replacements are constantly being built and launched into orbit e The Control segment which consists of ground stations located around the world that make sure the satellites are working properly e The User segment the GPS receivers used by the community eg ETrex device Space Segment Figure 1 The 3 GPS segments This satellite based system offers highly precise location data for any point on the planet in any weather conditions 24 hours a day It is mainly used for navigation positioning and other research applications 09 25
10. cated matches the current date ere e Press UP DOWN buttons e Highlight YES and press the ENTER button the eTRex will continue tracking satellites and switch to the Satellite page b The date is incorrect e Press UP DOWN buttons e Highlight NO and press the ENTER button the eTRex will do an AUTOLOCATE and switch to the Satellite page An AUTOLOCATE forces the eTrex to search for any available satellite to determine its location 3 You are not indoors but you are far from the place where you turned the eTrex on more than 800 km Press the UP DOWN buttons Highlight NO Press ENTER eTrex then asks HAVE YOU MOVED HUNDREDS OF MILES KM SINCE LAST USE Press UP DOWN buttons Highlight YES Press ENTER eTrex will do an AUTOLOCATE and switch to the Satellite Page 4 4 I am not getting an accuracy higher better than 20 meters 1 Wait 5 minutes on the same location 2 Ifthe situation does not change after 5 minutes Move to a new location with a clear view of the sky The best location would be in order of preference e The front door of the building house for building try to see if it is not possible to go on the roof e The side of the building house e A parking lot or a park close to the building house 4 5 eTrex does not display the desired units when making the accuracy or co ordinates reading Check to make sure the eTrex is configured to use the Position Format
11. ceivers are inexpensive GPS data is free and survey staff can be trained quickly to their use By knowing the geographic location of each cluster it will be for example easier to go back to the same place for supplementary data collection With the geographic location it is also possible to use the information collected by the receiver within the Geographic Information Systems GIS A GIS can be defined as being a computer system for capturing storing checking integrating manipulating analysing and displaying data related to a position on a surface AGI dictionary By integrating the location of the WHS clusters into a GIS it will firstly be possible to examine the relationship that may exists between the data collected and the infrastructure located within or around the clusters This concerns for example health facilities roads market water pumps and so on If the location of these 1s known the GIS tool will be used to calculate the distance to the nearest infrastructure and include this information into the survey analysis to extract figures at the cluster level from other spatially distributed information such as Digital Elevation Models altitude environmental parameters climates landuse and use them in multivariable analysis to aggregate the clusters according to new units of analysis such as climatic zones or ethnic regions to extrapolate some of the figures collected by the survey using other g
12. e signals strong enough to know its location and that you can start to use it The location accuracy message that is displayed when the device is ready to be used ACCURACY The value given is an indication of the precision that the device is able to offer regarding its position based on the satellite s localisations The number of satellite signals that the receiver is tracking indicated by the drawing in the middle of the screen Each line between the character and a satellite indicates a connection On the Figure 13 for example the device 1s actually receiving the signal from 3 satellites The satellite Signal strength bar which indicates the intensity of the satellite signal received When the bar is full black the signal is generally strong enough to allow the use of the device From this main page it is possible to have access to two sub pages as indicated on Figure 14 DISPLAY LIGHT TIMEOUT MEE CONTRAST b HAIT LOCATING SATELLITES OPTIONS Display Page ADVANCED SK TUIEM READY TO NAVIGATE ACCU Satellite Page Normal SkyView Satellite Page Advanced SkyView Figure 14 Scheme to access the DISPLAY and ADVANCED SKY VIEW pages from the NORMAL SKYVIEW SATELLITE page 15 09 25 02 GPS field guide 8 19 A9 P9 You can access to these two pages by pressing the ENTER button from the NORMAL SKYVIEW SATELLITE page in order to open the OPTIONS window From there you can us
13. e the UP and DOWN buttons to highlight the page you want to access and press the ENTER button Once you have finished working on one of these pages you can come back to the NORMAL SKY VIEW SATELLITE page pressing the PAGE button again Figure 14 The DISPLAY page This page allows you to setup the back light time out and the display contrast The first element may be useful for night reading and it is 1mportant to setup the contrast correctly in order to insure a good reading of the information on the LCD screen When you arrive on this page the LIGHT TIMEOUT field is highlighted and you can make the scrolling menu by pressing the ENTER button Figure 15 a Once you have selected the desired time press the ENTER button to save the option It is recommended to choose 30 seconds as this option uses a lot of battery power You can then pass to the contrast option pressing the DOWN button Once the contrast bar is highlighted Figure 15 b press the ENTER button You can then use the UP or DOWN button to modify the contrast until you get an appropriate reading on the screen Then press the ENTER button to save the setting a DISFLAY b DISPLAY LIGHT TIMEOUT LIGHT TIMEOUT 20 SECONDS CONTRAST STATS Of 1E SECONDS MINUTES Figure 15 DISPLAY page with the LIGHT TIMEOUT menu a and the contrast bar highlighted b 16 09 25 02 GPS field guide 8 19 A9 P9 The ADVANCED SKY VIEW SATELLITE page This page co
14. eographically distributed parameters which include modelling capabilities With all this information being implemented in the GIS tool it will then be possible to have a first picture of the distribution of the poor Knowing where they are located could then be used to know if this distribution 1s related to the distribution of other parameter health education The use of GIS will also help in the creation of thematic maps that will be used in presentations and or reports Finally GIS could be used in the future in order to help designing the sampling frames and the GPS used to find the location of the selected clusters 09 25 02 GPS field guide 8 19 A9 P9 CHAPTER 3 THE GARMIN ETREX UNIT The Garmin eTrex GPS receiver has been chosen for the WHO WHS because it is easy to use and inexpensive Its utilisation in the context of different surveys operated in the field has proven its suitability for this kind of work This device is completely waterproof runs for approximately 22 hours on two AA alkaline batteries and can operate under dense tree canopy The present section describes the receiver as well as the operating system allowing the user to measure the geographic co ordinates Information about how to use the receiver is provided in the Quick Reference Guide and in the GPS data collection protocol 3 1 Overview of the unit One of the advantage of this receiver is the reduced number of elements and buttons on the unit Fi
15. ge Figure 20 allows the user to customize the eTrex This page contains a list setup pages In the context of the WHS survey we only need to deal with two of them the UNITS and SYSTEM ones the DISPLAY page corresponds to the same page as the one described under section 3 2 3 1 To access the desired setup you have to highlight its name in the list using the UP or DOWN buttons and press the ENTER button Li TIME DISPLAY fom UNITS M ai INTERFACE tz T OS SE ZED 06 HAR OO Figure 20 The SETUP option page 19 09 25 02 GPS field guide 8 19 A9 P9 The UNITS setup page This page Figure 21 allows the user to setup the units of the different parameters It is important to make sure that this page contains the setting specific to the WHS as indicated in the Figure 21 a and in the Quick Reference Guide a MTS OTS b FOSITIDN FRET POSITION FRAMT hadd ddddde MAF DAT hadd mm mm HGS 24 HITS Eritish Grid METRIC SETAn ana I I NORTH REF Haidenhead PAS HET IC WAPI ARE swedish Grid 3 noo Ln ANGLE DEGREES DEGREES Figure 21 The UNITS page a with the scroll down list b To change the value or format in a specific field you have to first highlight it using the UP or DOWN button e g the position format field on the Figure 21 Press the ENTER button to make the corresponding scroll down list appear from which you will select the desired format or value Figure 21 Press the EN
16. gure 9 and 10 1 Internal GPS Antanna DOWN Button E er Bultory LCD Display with backlight Figure 9 Front view of the Garmin eTrex device 10 09 25 02 GPS field guide 8 19 A9 P9 External Power and Data Connector 9 T Waterproof Case 6 Battary Campartment Figure 10 Back view of the Garmin eTrex device Table 1 describes the elements reported on the Figures 9 and 10 Inside the waterproof case are located a set of electronic components that allow the receiver to perform different operations and to display the final result on the LCD screen through a specific operating system The case also contains an internal built in clock and memory that has the capacity to store the data received through the satellite signal like the almanac data Depending on the GPS provider the POWER PAGE and ENTER buttons are not identified with the same symbols as the ones reported on the Figure 9 but as follow Aiz 11 09 25 02 GPS field guide 8 19 A9 P9 1 Internal GPS Antenna This antenna allows the receiver to track satellites signals Thus when using the GPS the unit should be parallel to the ground and facing upwards Apart from the cover of the holster nothing should be put on this part of the unit as this may stop satellite signal 2 LCD Display Screen Screen where all the information is displayed The LCD Display is one fragile part of the eT Rex it may be injured and
17. his will mean that the receiver is located somewhere on a sphere that is centred on this first satellite and that has a radius of 17 000 km Figure 3 PN Satellite 1 17 000 km Figure 3 Sphere indicating the potential location of the GPS receiver with one satellite signal 2 Calculates the distance to a second satellite for which it is able to catch a signal 19 000 km for example This tells the receiver that it is not only located on the first sphere Figure 3 but also on a second sphere centred on the second satellite and that has a radius of 19 000 km Or in other words that the receiver is somewhere on the circle where these two spheres intersect Figure 4 point a Figure 4 Circle indicating the potential location of the GPS with two satellite signals a 09 25 02 GPS field guide 8 19 A9 P9 3 Repeats the operation mentioned under point 2 with a third satellite In our example the receiver finds out that it is 20 000 km from the third satellite which narrows its position down even further to the two points Figure 5 point b where the 20 000 km sphere cuts through the circle reported on Figure 4 corresponding to the intersection of the first two spheres Figure 5 Potential locations of the GPS receiver with 3 satellites signals b Most of the time one of these two points is absurd and is rejected by the receiver that is then able to give the exact location In some cases a fourth satellite 1s necessary to
18. ly will not work indoors underwater or underground 09 25 02 GPS field guide 8 19 A9 P9 There may also be sources of signal multipath i e on Figure 8 occurring when the GPS signal is reflected off these objects before reaching the receiver This increases the travel time of the signal and creates errors of distance estimation between the satellite and the receiver ty Figure 8 Example of multipath GPS signal connected to buildings or mountains This underlines the importance for the users to be located in the most open area as possible before taking the measurement There are other sources of error over which the user does not have control including e Atmosphere delays The satellite signal slows as it passes through the atmosphere The GPS system uses a model that calculates an average amount of delay to correct for this type of error e Receiver clock errors A receiver s built in clock is not as accurate as the atomic clocks onboard the GPS satellites Therefore it may have very slight timing errors e Orbital errors Also known as ephemeris errors these are inaccuracies of the satellite s reported location 09 25 02 GPS field guide 8 19 A9 P9 CHAPTER 2 WHY USING GPS IN THE CONTEXT OF THE WHO WHS The first reason for using GPS in the WHS context is the added value it gives to the survey by allowing the geographical dimension to be taken into account without requiring important investment many GPS re
19. n presented on the Quick Reference guide 3 2 1 Installation of the batteries To install the batteries remove the battery cover Figure 10 by turning the D ring at the back of the receiver 1 4 turn counter clockwise Insert the batteries into position observing proper polarity Attach the battery cover by turning the D ring 1 4 turn clockwise Important Battery Installation Information Warning Improper installation may cause damage and or battery leakage Be sure to observe the proper polarity when inserting the batteries It is very important to install the TWO batteries with the proper polarity positive and negative orientation as indicated in the unit s battery compartment and in the Quick Reference Guide Remove the batteries from your eTrex if you don t expect to use it for several months 3 2 2 The eTrex operating system In order for the user to read information and setup the unit the eTrex receiver contains an operating system To access this system hold the unit so the built in antenna the flat area above the display is parallel to the ground the screen facing upwards Press and hold the POWER Button firmly to turn on the unit The WELCOME page Figure 11 is then displayed on the screen while the unit conducts a self test a Once testing is complete this page will be replaced by the NORMAL SKY VIEW SATELLITE which represents the first copuriaht 2000 element of the operating system GARMIN Corp
20. ntains the same elements as the NORMAL SKY VIEW SATELLITE page but presented in a different graphical way Figure 16 This display gives more information about the location of the satellites in the sky represented as a numbered square around your location the point at the centre of the screen In the Figure 16 the GPS device is surrounded by 9 satellites 7 of them have a signal strong enough to be received square in black one in grey having a signal not strong enough and the last one not being read by the device the n 20 This display is very helpful to check the Positional Dilution of Precision PDOP see section 1 3 In case you have difficulty finding satellites because it also can help you to identify obstacles that might block the signal such as buildings mountains For that you may use the North indication on the screen to orient the unit status Message READY TO HAUIGATE North ALCURALT Indication Location Accuracy Your Location Satellites Satellite Signal Strength Bars Figure 16 ADVANCED SKY VIEW page 3 2 3 2 The MENU page The MENU page Figure 17 presents a list of options as well as the indication of the Time Date and Battery strength This last element can help the user to identify when to replace the batteries 17 09 25 02 GPS field guide 8 19 A9 P9 Options Time and Date Battery Strength le 1 DEC DE Figure 17 The MENU page There are two options of i
21. nterest for the WHS on the MENU page the MARK and SETUP ones The Figure 18 allows you to visualise how to access to the structure of these two options UNITS MARK _ WAYPOINT fae HA MAF DATUM WGS 34 METRIC en MAGHETIC VARIANCE CO ANGLE DEGREES i r HWHAYFOINTS PEP ROUTE fe TRACKS i SETUP O amp 24d 1ldpm 31 DEC o05 SYSTEM W DISPLAY MODE LANGUAGE English SOFTHARE VERSION 2 03 aes ga UNITS i INTERFACE g UISIT HHH GARMIN COM FOR LATEST SOFTWARE UPDATES Figure 18 Scheme to access the MARK and SETUP option pages To access to the selected option you have to highlight it in the menu using the UP or DOWN button on Figure 16 the MARK option is highlighted and press the ENTER button Once you have finished working on one of these pages you can come back to the MENU page by pressing the PAGE button 18 09 25 02 GPS field guide 8 19 A9 P9 The MARK WAYPOINT option page Once the GPS receiver has been set up and that the user has found an open area for the reading this page will allow the user to visualise his location Figure 19 The other information or options reported on this page will not be used in the context of the WHS HARK HATE OIA T Coordinate ELEN S42 m H 240200 E094 360 20 Figure 19 the MARK WAYPOINT option page The SETUP option page The SETUP option pa
22. point 1 place a fresh set of AA batteries in the unit refer to Quick Reference Guide point n 3 Installing the Batteries and use Alkalyne batteries as they have a longer life 3 IfeTrex still does not turn on the problem requires the help of a technician please contact your supervisor 4 2 The message READY TO NAVIGATE Pr t naviguer does not appear on the screen 1 There may be large obstacles around you that stops the satellite signals move to a new location a large open area with a clear view of the sky 2 Another window with a message may appear see section 4 3 for the list of these messages and their explanations 4 3 The message TROUBLE TRACKING SATELLITES ARE YOU INDOOR NOW appears on the screen 1 You are indoor EER Press the DOWN Button SATELLITES Highlight YES and press ENTER ATA Go outdoor for the receiver to catch satellites signal as the GPS unit INDOORS cannot receive the satellite signals when you are seth indoors NO 2 You are not indoors and you are close to the open place where you turned the GPS on less than 800 km Press the UP DOWN buttons va Highlight NO De Press ENTER OF MILES KM eTrex then asks HAVE YOU MOVED HUNDREDS OF reste 3 MILES KM SINCE LAST USE Press UP DOWN buttons Highlight NO Press ENTER 21 09 25 02 GPS field guide 8 19 A9 P9 eTrex then asks IS TODAY dd mmm yy Two possibilities arom a The date indi
23. t position It is a measure based solely on the geometry of the satellites in the sky Ephemeris The predictions of current satellite position that are transmitted to the user in the data message Initialization Refers to the procedure of telling a GPS receiver where it is when it 1s turned on for the first time Information required for initialization includes approximate present position in latitude longitude coordinates the current local time and date information obtained through the satellite signal when using the eTrex unit Map Datums Since the Earth is not flat a model needs to be used in order for the GPS receiver to give the coordinates These models are calls Datums Multipath Mutipath is the phenomena by which the GPS signal is reflected by some object or surface before being detected by the receptor antenna creating multipath for a same signal that results in a calculation error when estimating the distance between the satellite and the receiver Position A geographic location on the earth commonly measured in latitude and longitude Satellite constellation The arrangement in space of a set of satellites Segment One of several parts or pieces that fit with others to constitute a whole object GPS Control segment A Master Control Station and a number of monitoring stations around the world that ensure the accuracy of satellite positions and their clocks GPS Space segment The network of 24 GPS satellites GPS
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