“g” Version 2 - Micro
Contents
1. oe ACOSTE WWW MICROGLACOSTE COM g6 User s Manual MARCH 2006 06 Absolute Gravity Data Acquisition and Processing Software Table of Contents Introduction 4 System Requirements 4 Installing g 5 Post Mission Processing 6 g Binary Data Files Structure 6 How g works 6 Starting g 7 The State Window 8 Drops 9 Fit Residuals 9 Sets 11 The Set View Control Window 11 Processing Data 13 Reviewing Processing Parameters 13 Start Processing 14 Processing Status 15 Processing Finished 17 Reviewing Processing Results 17 Project Summary File 17 Set Summary File 18 Additional Window Displays 19 Processing Control and Gravity Corrections 20 Barometric Pressure 21 Polar Motion 21 Reference Xo 22 Datum Height 22 Tidal Correction 22 System Response 23 Laser Control 23 Seismometer 24 Fringe Data 24 96 Absolute Gravity Data Acquisition and Processing Software Fit Sensitivity Statistics Modeling System Environmental Set up Default Settings Real time Data Processing Information System Instrument Seismometer FGL Only Computer Interface Cards Acquisition Modes Sampling Time Rates Red Blue Sequencing Control General Terms Tidal Terms System Response Laser Seismometer Drop Fit Fit S2. 3 Drop Interval s 1 Pulse Delay s 05 Throw Figure 15 Process Setup Acquisition Dialog Box Modes Currently only the drop mode is enabled Sampling Sets The user may select the number of Sets to acquire during the project Drop Set The user may selected the number of drops in each set during acquisition 29 N Time e Start Immediately Instructs the software to begin data acquisition immediately following Process Go or F5 e Start at Specified Time Instructs the software to begin data acquisition at the time indicated 06 Absolute Gravity Data Acquisition and Processing Software IMPORTANT Time on the PC Clock must be set to Coordinated Universal Time GMT not local time with daylight savings disabled Rates Drop Interval Used to select the drop rate interval in seconds Recommended rates are system dependent Please consult the system manual e Set Interval Used to select the interval in minutes at which to start new sets The drop down menu contains some commonly used intervals e Pulse Delay This is the amount of time in seconds between the drop and the time the object is lifted Systems with digital controllers need much less time to lift than do systems with analog controllers approximate value is set automatically by g Red Blue Sequencing Red Blue sequenc
3. Set Gravity Uncertainty Set Scatter Drop Scatter Number of Sets Attached Files E mail Sent Project File SetFile Never Suppress Error Messages OK Figure 22 Email notification setup window Output There are three options under Output Text Raw Dump and Graphics By default g outputs a text file for Project Summary and Set by Set Summary If users wish to have additional information output to file Drops Graphics jpg image of the displayed view or Raw Data these options must be selected before processing the data Note The view must be opened for g to save the graphical images N Additional Utilities Convert Convert is the utility used for converting files obtained with Olivia DOS software into the new g format Figure 23 shows the Convert menu g6 Absolute Gravity Data Acquisition and Processing Software Convert X Input File Path Name Freefall Project Dutput Project Directory A Convert Now Figure 23 Convert Utility Dialog Box Input File Path Name This is the name of the DDT or compatible binary absolute gravity data file 2 Convert supports most DDT files but may not support some versions If you have trouble converting files please contact MGS immediately e Freefall Project Name This is the base name to be used with the g project file Output Project Directory This is the location at which all
4. 5 The Process Setup menu performs as data acquisition and data processing electronic notebook There are five tab dialog windows contained in the Setup menu Information System Acquisition Control Comments Site Setup Lookup Name Micro g Solutions Inc Ref Height 14 Code MGSNU Baro Fact uG mBar 03 Polar X arc sec 0 1823 Latitude dd N 4002885 Polar Y are sec 83169 Longitude dd E 105 04603 Datum Hat 100 Elevation 1528 Set To Top Of Drop Nominal Pressure mBar 842 65 Sef Gradient uGal cm 3 02 Access Point File Figure 8 Process Setup Dialog Box e Information This menu is concerned with where the instrument is located user can enter Site Name Site Code Latitude DD Longitude DD Elevation m Mean Sea Level Nominal Pressure mBar Gradient uGal cm Datum Height cm Measured Reference Height cm Barometric Factor uGal mBar Polar motion X component arcsec Polar motion Y component arcsec System This menu allows the user to enter Instrument Type Model Serial Number Interferometer Type Laser Type and wavelengths if applicable Seismometer data collection enabled if applicable FGL Series instruments only Fringe Card type and setup Analog to Digital data acquisition card and setup Serial Barometer set
5. Analog 537 5 125 o User Sensor 5 BiPolar 5V 0 1 o User Sensor 6 BiPolar 5V 0 1 o User Sensor or Seismometer 7 BiPolar 0 3125V 0 1 e Advanced The Advanced button should only be used by knowledgeable users Options settable under the Advanced menu include o Factory Height Instrument Specific and Set ONLY by Micro g LaCoste This is the sum of all the internal hardware heights Please refer to your instrument materials for a precise value o Clock Frequency Nominally 10 MHz but is calibrated by Micro g LaCoste or a standards laboratory o System Offset FGL and A10 ONLY as determined by Micro g LaCoste Q Q Q 3 Serial Barometer use the offset and multiplier inside the A2D card set for scaling 28 06 Absolute Gravity Data Acquisition and Processing Software o Hardware TTL Prescale Factor Determined by Micro g LaCoste Typically this value is 1 but certain instruments have the fringe information prescaled at the hardware level Please refer to your instrument materials for the correct value Acquisition The Acquisition set up page 1s shown below Setup lt Information System Acquisition Control Comments Time Start Immediately Start at Specified Time Thu Mar 10 2005 10 57 49 EE z Sampling Sets 30 Red Blue Sequencing Drops Set 120 Enable Sequence Interval min go Rates A Su inva gt gt Red Blue Interval
6. Users may select from a variety of seismometer options supported by Micro g e Sampling Frequency Users may enter the sampling frequency Recommend is 10xCutoff e Sampling Time Users may enter the amount of time to sample Recommended is 200ms for small dropping chambers g6 Absolute Gravity Data Acquisition and Processing Software Computer Interface Cards e Fringe Card Currently Micro g supports only the GuideTech ISA or PCI GT650 series time interval analyzer in real time acquisition The Setup button allows the user to change the default location of the GuideTech configuration file the base address of the card the Input Multiplexor and Scale Factor an number of fringes to acquire Recommended parameters are o FPG File c Program Files Guide GT650 FPGA gt65x2 fpg o Address 0 Input Multiplexor 4 Pre Scale 250 100 for Small Dropping Chambers o No Fringes Acquired 700 e Currently g supports the IOTech 200 ISA or 2000 PCI series A2D boards and the National Instruments PCI 6013 A2D board The SETUP button allows the user to set the acquisition parameters for each channel For the standard Micro g configuration these parameters should be for Channel s respectively o Temperature 0 UniPolar 1 25V 0 100 Super Spring 1 BiPolar 1 25V 0 1 Ion Pump 2 BiPolar 5V 0 1 Laser Voltage 3 BiPolar 5V 0 1 Barometer 4 UniPolar 1 25V 0 1 Serial Barometer 0 68 947 A
7. 1 1217 2 0128 ijg Acquisition Version g Processing Version Company Institution DPR Juan Diego Montoya Station Data Name Micro g Solutions Inc Site Code MGSNU Lat 40 02885 Long 105 04603 Elev Reference Height 14 00cm Datum Height 100 00cm Gradient 3 02uGal cm Nominal Air Pressure Barometric Admittance Factor Polar Motion Coord 0 183 1528 00m 842 65mBar 0 30 0 317 Instrument Data S N Factory Height 116 30cm Rubidium Frequency 10000000 00000Hz Laser 67881k34 ID 632 99117754nm 0 36V IE 632 99119473nm 0 73V IF 632 99121259nm 1 03V IG 632 99123023nm 1 30 IH 632 99136890nm 1 43V II 632 99139822nm 1 20 IJ 632 99142704nm 0 90 Modulation Frequency 8333 420Hz Processing Results Date 01 10 02 Time 05 46 36 DOY 010 2002 Gravity 979647292 67uGal Set Scatter 2 26uGal Measurement Precision 0 5 1 Total Uncertainty 2 24uGal Number of Sets Collected 12 Number of Sets Processed 12 Set 5 Processed 1 2 3 4 5 6 7 8 9 10 11 12 of Sets NOT Processed 0 Set 5 NOT Processed Number of Drops Set Total Drops Accepted Total Drops Rejected Total Fringes Acquired Fringe Start 30 Processed Fringes 600 GuideCard Multiplex 4 GuideCard Scale Factor 100 1193 7 700 250 Gravity Corrections Earth Tide Berger 51 97uGal Tidal DC Term 1 00 Polar Motio
8. 1992 is used The formula reads 1 164x10 25 pcos g xcos ysin A where dg polar motion correction in Gals earth s angular rotational velocity rad s a semi major axis of the reference ellipsoid m geodetic latitude rad geodetic longitude rad x y polar coordinates in the IERS system rad Mean pole positions are determined at daily intervals and issued daily by the IERS Bulletin The Bulletin A containing the polar motion coordinates in final and predicted format is available at no cost on the web at http maia usno navy mil bulletin a html In addition the Micro g LaCoste website http www microglacoste com has daily updates of the polar motion as well 21 N Reference Xo In the equation of motion as used g gravity is determined at to not at xo In order to calculate the gravity at the reference position the distance to the start position 18 multiplied by the site gravity gradient and used to correct the final calculated gravity value This correction is generally very small lt 0 05uGal 06 Absolute Gravity Data Acquisition and Processing Software Datum Height The gravity value is actually determined at the top of the drop inside the instrument dropping chamber This height can vary from instrument to instrument and is in general a not so useful location However the observed gravity for each drop can be transferred to a user s
9. Datum Transfer and Reference Xo Units are in Gals e Set Fit Sensitivity Displays the set standard deviations Drop Histogram Displays a histogram of the processed drops for the currently processed set In general users should expect to see normally distributed data Drop Sensors Displays up to six separate charts for the currently processed set Charts 1 5 show the default channels for a Micro g Patch Panel Temperature Super Spring Ion Pump Laser and Barometer The sixth chart is reserved for channels 6 7 and 8 and stacks all three channels onto one graph if enabled Drop Corrections Displays six separate charts one for each type of correction applied to the calculated gravity value for the current set Tide Ocean Loading Polar Motion Barometric Datum Transfer and Reference Xo Units in ui Gals Drop Parabola Displays the trajectory of the object with time on the X axis and distance on the Y axis This graph is useful to view dropping chamber and fringe data acquisition performance Drop Seismometer This view is applicable for LS meters only and has two components If seismometer data is used directly in the solution the graph shows the compensated versus uncompensated residuals nm If the seismometer data is NOT used in the solution the graph shows the seismometer velocity mV Drop Residual PSD This view shows an autoscaled PSD of the residual signal ONLY IF Frequency Response is
10. Figure 10 State Window As previously mentioned the State Window is always displayed and contains the most information of any of the twelve views In Figure 10 basic project setup information is shown in the top window including the position 40 02885 105 04603 1528 nominal pressure 842 65 gradient 3 02 the instrument type and serial number FG5 206 and the acquisition parameters 12 sets 100 drop set 60 minute set intervals 10 second drop intervals In order to display information to the user and keep the view uncluttered many of the boxes are NOT labeled However by hovering the mouse cursor over each box a tool tip including units will appear with a description of the value The second box Drop contains information pertaining to the current drop being processed In the case of Figure 10 the drop is 100 The time of the drop is displayed 01 24 56 the corrected absolute gravity value of the last drop 979647287 69 the standard deviation of the drop 26 39 the RMS of the drop fit nm 0 93 the drop number 100 whether or not the drop was accepted or rejected and the peak lock aE implies accepted E lock The next six boxes show the corrections in uGal for tide 25 00 ocean loading 0 0 polar motion 6 66 barometric 1 80 datum transfer 91 51 and reference Xo 0 01 The final six boxes show the current value of the 16 N sensor channels for ONLY the fir
11. average residual of the accepted drops If the instrument is working properly the blue signal should ALWAYS be smaller in amplitude than the green signal Ifa drop is rejected it s residual signal is plotted in red If system response is enabled Figure 5 see System Response discussion below the orange signal is the compensated residual vector from the current drop the green signal is the uncompensated residual vector from the current drop and the purple signal represents the compensated average residual of the accepted drops 06 Absolute Gravity Data Acquisition and Processing Software E J Ah il ai il M ULLA IBN ERE 1 anm _ Pa PP T RPM am LS 5 Figure 5 Drop Residuals System Response Enabled N Sets The Sets view displays individual set gravity values minus the mean value of the project g6 Absolute Gravity Data Acquisition and Processing Software Each set is plotted with an error bar that indicates the range of the uncertainty for the individual set based on the drop scatter The top of the view informs the user of the current cumulative mean for the project the set to set scatter and the total uncertainty of the project mean As of g6 the current set value will be updated with each drop this is true after the first set is complete This allows quick veri
12. enabled Drop Fit Sensitivity Top and Bottom Displays the change in the calculated gravity value as different portions of the drop fit are selected Values are displayed relative to the value determined at the nominal fit selected in Setup Control See Fringe Data and Fit Sensitivity below 19 IMPORTANT Viewing many displays can significantly slow down data processing and this can in turn result in potential memory violations If your system does NOT have a high end graphics card gt 32mb on board memory minimize the number of open views 06 Absolute Gravity Data Acquisition and Processing Software FAST To Tile or Cascade views press or Processing Control and Gravity Corrections g allows the user to apply all the recognized corrections to the trajectory acceleration to determine an accurate value for absolute gravity These corrections are turned on or off at the Process Setup Control page The Control page is shown in Figure 12 Information System Acquisition Comments General Terms gt r Laser Barometric Pressure Auto Peak Detection v Polar Motion Peaks wEo1 0D E 7 Ref X WEDO Wavelength Modulation eference Xo v Datum Height Seismometer atum Compensated Sep Drop Fit Fit Sensitivity Start Time 35 03 ms Stop Time 199 95 ms 25 41 ms Start Fringe 19 Total Fringes Stop 44
13. g converted files FG5 and gsf will reside Additional Utilities gProjectMerge gProjectMerge is a program that lets users combine multiple projects into one single project file This is useful in the case when data acquisition is interrupted and a single project is desired Note that gProjectMerge assumes that all acquisition parameters are identical i e perhaps a run was stopped after a few sets and a new project was created and begun immediately gProjectMerge is not intended to combine projects with different parameters if doing so it is at your own risk Figure 24 shows the gProjectMerge interface 42 96 Absolute Gravity Data Acquisition and Processing Software Figure 24 Project Merge Dialog Box e Output Directory This is the location where the merged project will reside e Final Project Name This is the name which the merged project will be saved as e Merge Files These are the files that will be merged together to create the merged project e Add File Button This button is for adding more files to the Files list Remove File Button This button is for removing files from the Merge Files list This button will remove the selected item If no items are selected it will remove the first item e Merge Button This button is used to start merging the file 2 Additional Utilities gProjectCopy gProjectCopy is a program that lets users easily change t
14. gsf txt file with the fringe data again in the correct format which g will open automatically The ASCII data are then converted to the standard g format for processing Edit Reset This option allows users to reset all or some of the project file parameters to the values at the time of original data acquisition Time Offset This option allows application of a time shift in the event that the computer time was not set to the correct time To calculate the offset change the True Start Time to the correct time the time that should have been and then press Calculate Check the time offset as listed in the grayed edit box If the time offset is correct check the Apply Time Offset option to make the time offset effective during processing Original Start Time 2002 Jan 24 16 29 30 True Start Time 2002 Jan 24 16 29 30 Time Offset D h m s 0 00 00 00 Apply Time Offset Cancel Calculate Figure 20 Project Time Offset Dialog Box Process Rate This option sets the rate at which drops are processed in Post Mission mode only On some machines with slower graphics it may be necessary to set the rate to 50ms or N greater in order to avoid synchronization problems occurring between mathematical processing and graphical display g6 Absolute Gravity Data Acquisition and Processing Software Set Break Point This option allows the manual setting of a break point in Post Mission mode o
15. of the modulation frequency and the precise value for your laser The actual frequency should be entered in Setup System Laser Setup WEO 200 lasers are also supported but there is no peak detection nor modulation frequency information that is needed 23 N For 1 AL 1 lasers the user can select the red or blue wavelength or select Alternate In Alternate mode the software will send an impulse signal through the digital output of the patch panel and switch between the two modes between each set Blue lock sets will be displayed in blue on the Sets view while Red lock sets will be displayed in Red g6 Absolute Gravity Data Acquisition and Processing Software Seismometer If data are taken from an FGL meter enabled with the seismometer option FGL this box can be checked to apply the seismometer signal The compensated signal is determined by integrating the seismometer velocity and subtracting the result from the trajectory This option is only valid with the FGL option Fringe Data In this section the user can select the starting fringe from which to process data and the number of fringes to include in the trajectory Starting with g v5 0 the user now enters nominal times for the fit typically 30ms after the start of the drop and 5ms before the catch portion of the drop and the program will determine the nearest integer fringe values for both the start and end of the fit Fit Sensitivity Once the n
16. phase Kappa of zero This delta factor cannot be modified except for the DC term Honkasalo correction The tidal potential is also set once for all The gravity body tide is computed and applied to the observations each drop The program used for this computation was originally written by Jon Berger November 1969 and was modified by J C Harrison Judah Levine and Karen Young University of Colorado Duncan Agnew University of California San Diego and Glenn Sasagawa NOAA ETGTAB If ETGTAB is selected from the drop down list box the Setup button leads to the menu shown in Figure 17 The Setup dialog has three separate sections For more advanced information you can contact Olivier Francis at Olivier ecgs lu 33 06 Absolute Gravity Data Acquisition and Processing Software Setup Information Potential Filename General C Program Files Micro g Solutions Inc ETCPOT DAT or equivalent Ocean Load Files Delta Factor Filename Model Observed 09 jan 02a dff s ETGTAB INI dff or equivalent Ocean Loading Filename On Off 09 jan 02a olf ana Setup Run Ocean Load Default Setup Apply Figure 17 ETGTAB Setup Dialog Box Potential Filename The first section allows the user to enter the Tidal Generating Potential File For most users this file is called ETCPOT dat and
17. uGal All others Gradient 0 03 uGal cm For experienced relative meter operators Default Settings On the lower left hand corner of the Uncertainty Setup page is a drop down dialog box and an Apply button To set the MGS recommend guideline values for a specified instrument choose the appropriate instrument in the dialog list and press the Apply button 26 N Real time Data Processing g6 Absolute Gravity Data Acquisition and Processing Software g allows both real time data acquisition and post mission processing To begin a data acquisition project choose Project New from the main g menu The four default screens will appear but there will be no information in the Set Tree view By default g is set to run FG5 instrument at the Micro g LaCoste facility set the software up for data acquisition and processing at your location you must modify some or all of the parameters under Process Setup Information This menu is concerned with where the instrument is located The user can enter Site Name Site Code Latitude decimal degrees DD Longitude DD Elevation meters above sea level Nominal Pressure mBar this is the long term mean pressure value at the site which is in generally not the current pressure value Gradient uGal cm Datum Height cm Measured Reference Height cm Barometric Factor uGal mBar Polar motion X component arcsec Polar motion Y component arcsec The user may choose to ente
18. 74 ms Bottom Start 135 05 ms Update Fringe Windows Stop 205 05 ms ETGTAB Setup System Response Compensation Apply Setup Reject Sigma 3 Setup Tidal Terms Uncertainty Figure 12 Process Setup Control Dialog Box 20 N Barometric Pressure The observed gravity is normalized to a nominal pressure at each site by applying a correction based on the observed atmospheric pressure during the observations This pressure correction is applied at each drop The formula used to compute the pressure correction is g6 Absolute Gravity Data Acquisition and Processing Software C p A P n where A The barometric admittance factor uGal mBar specified in the Information Setup This value is usually between 0 30 and 0 42 The recommended value per IAG 1983 is 0 30 C p Barometric Pressure Correction in uGal P o Observed barometric pressure P n Nominal barometric pressure in accordance with DIN Standard 5450 Polar Motion This correction compensates for changes in centrifugal acceleration due to variation of the distance of the earth s rotation axis from the gravity station This correction is normally re computed using pole positions that are determined nearest to the observation time for each station The formula specified in the IAGBN Absolute Observations Data Processing Standards
19. Gal Uncertainty of the final value uGal Number of sets Collected Number of sets included in the processing Sets included in the processing Number of sets NOT processed Sets not included in the processing Number of drops in each set Total number of drops accepted in processing Total nubmer of drops rejected in processing Fringes acquired during each drop Starting fringe from which to process Number of fringes to include in processing Guide Card Multiplex setting Guide Card Scale Factor setting Gravity Corrections Section Average Earth Tide Correction and Model Selected Tidal DC term used for earth tide correction Average Polar Motion Correction Average Barometric Pressure Correction Average Datum Height Correction Average Reference Xo Correction Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Uncertainty Summary Section Component due to Component due to Component due to Component due to Component due to Component due to Component due to Component due to Component due to Component due to Component due to Component due to Earth Tide uGal Ocean Load uGal Barometric uGal Polar Motion uGal Laser uGal Clock uGal System Type uGal Tidal Swell uGal Water Table uGal Unmodeled uGal System Setup uGal Gradient 1 Figure 11 project txt Output Summary File Set Su
20. Set 2 g6 Absolute Gravity Data Acquisition and Processing Software Erie 09 02a J lej xj Broject Edt view Process Options Output Window Cf oo Erie 09 jan 028001 gsf Erie 09 jan 02a002 gst Erie 09 jan 022003 98 Erie 09 jan 022004 gst Erie 03 jan 022005 asf Erie 09 jan 02a006 asf Erie 09 jan 02a007 gst Erie 09 jan 02a008 gst Erie 09 jan 023009 gst Erie 09 jan 02a010 9sf Erie 09 jan 02a011 gsf Erie 09 jan 02a012 gst Fit Residual Position 02225 105 04603 1 1528 842 65 302 100 Systm FGS 206 Acquisition 12 1 100 1 60 10 p Drop p Project 12 97964728769 2639 093 00361 oro 2 Tide 2500 Lowa 000 poir 6466 Set Scatter 180 pam 9151 Reo 201 AED Temp 0 231 000 Pres 4 848 64 Sping 1y 001 Laser 0 66 Seis 27 0 00 residuals nm Tide 1892 Load 000 6 66 PETI 171 9151 4001 Working Directory C lgSampleDatal Paused Timer 00 00 00 Figure 9 Processing Status after completion of Set 2 The Sets window in the upper left han
21. Tide 2500 Load 000 56 Gravity 979647289 79 Set Scatter 0 94 180 Datum 91 51 RefXo 001 Uncertainty 213 Temp 0 231 Ion 2 000 Pres 4 848 64 m Tide 134 Spring 1 0 01 Laser 3 0 66 sei Z 7 0 00 Set 11638 97964728894 222 919 Tide 1892 Loa 000 6 66 0 Polar 6 Baro 149 Datum 91 51 Ref Xo 0 01 Baro 1 71 Datare 91 51 Bm Accept Figure 3 State Window N e Setup Basic setup and station information is displayed here including Latitude Longitude Elevation Standard Pressure Gradient System Type System Serial Number Number of Sets Acquired or to Acquire for Realtime Number of Drops per sets Time interval in minutes between sets and time interval in seconds between drops Drop Information about each individual drop including time absolute gravity standard deviation RMS number accepted a or rejected r and Laser Lock code tide correction ocean loading correction polar motion correction barometric correction datum transfer correction reference Xo correction temperature C super spring position V Ion pump monitor V laser output V barometric pressure mBar and average seismometer reading V Set A group of drops is referred to as a set Information about each individual set including mean time of the accepted drops in the set mean absolute
22. ans file and d means directory Su gy Uva D9 If you MGS README TXT f Overview of installation procedures gHelp pdf f This document Setup exe f Install application for Windows 98 Machines gSysChk exe f System Password generation application gWaveFiles d Earth Tide and Ocean Loading Tide binary data files gSampleData d Sample data for practice processing LICENSE TXT Standard Software Licensing Information do not have ALL the listed files and or directories on your CD please contact Completely uninstall all previous versions of g Note that all users will need to generate a new gPWlInfo bin file if they are using g versions previous to 6 See installation details below Double click the Install application Follow the instructions It is highly recommended that you accept ALL default installation paths From the Micro g LaCoste Program files menu run the g6SysChk exe program and generate the SysChk bin file Email SysChk bin to Maryann King at mking microglacoste com and wait for her to send you gPWinfo bin This usually takes less than twelve hours during normal the business week Note that the files are unique for each computer so please send one file at a time Upon receipt of gPWInfo bin manually copy the file into the newly created bin directory of Micro g Solutions Usually c Program Files Micro g Solutions bin If a valid password is not found in the bin directory g issues t
23. ased on the estimated uncertainties for many different components of the measurement Components are grouped into four separate areas Modeling System Environmental and Set up Default values are determined from previous publications and from in house experience Environmental Modeling Earth Tides Factor 0 001 Load Factor 01 0 uGals 0 uGals Tide Swell 5 Water Table Barometric Polar Motion 1 uGals 0 05 uGals Unmodeled 0 uGals System Laser Clock 0 01 uGals 0 5 uGals Set up 1 uGals System Gradient Uncert 0 03 uGal cm 1 uGals System Gradient 0 31 uGals Uncertainty due to gradient depends on vertical transfer Update System Model FG5 Total quadrature Systematic Uncertainty 2 02 Cancel Figure 14 Systematic Uncertainty Setup Dialog Box Modeling Modeling uncertainties usually do not vary from station to station or among different instrument serial numbers or models Recommended values for modeling uncertainties are 1 0u Gal 0 05p Gal Barometric Polar Motion The errors for the earth tide and ocean load calculations are estimated as fractions of the size of the actual correction determined at the time of the measurement and are nominally Earth Tide 0 001 x Correction The default values are guidelines only For details including position and seasonal variation se
24. d corner of shows the two previously processed sets and their Uncertainty error bars The two sets are plotted with the mean subtracted The mean value is written above the graph The Fit Residuals window in the upper right hand corner of Figure 9 shows the average residual signal for Set 2 in blue and the single drop residual signal for Drop 100 Set 2 in green The Drops window in the lower right hand corner shows all the gravity values for Set 2 with the mean subtracted while the State window the lower left hand corner shows 15 N text information for Drop 100 Set 2 Set 2 and the cumulative average for the entire project g6 Absolute Gravity Data Acquisition and Processing Software Figure 10 is another look at the State Window also shown above State Setup Position 40 02885 1528 842 65 3 02 100 Spes 12 100 6 Project Drop 01 24 56 979647287 69 2639 093 10 o2 2 Tide 251000 656 Gravity 979647289 79 Set Scatter 0 94 Baro 180 Datum 91 51 RefXo 0 01 Uncertainty Temp o 231 1on 2 000 4 848 64 Tide 174 Spring 1 001 Laser 3 0 66 Seis zn 0 00 Load D Polar 6 66 Set 011638 9795647288 94 222 919 2 97 149 Datum 91 51 Tide 18 92 Load 0 00 Polar 6 66 Ref Xo 0 Baro 171 Datum 91 51 0 01
25. e Niebauer et al A new generation of absolute gravimeters Metrologia 1995 25 N Ocean Load 0 1 x Correction For example if at a given time the earth tide correction is 50 uGal then the uncertainty on the correction is 0 05 uGal 06 Absolute Gravity Data Acquisition and Processing Software System System uncertainties vary depending on what elements are contained in the absolute gravimeter system 5 are the most accurate and precise MGS instruments observations taken from these types of instruments should be weighted much more than those taken from an FgL Recommended values for modeling uncertainties are Laser 0 05 uGal 0 1 uGal ML 1 Clock 0 5 wGal Rubidium Oscillator System Model 1 1 Gal FG5 10 wGal A10 5 uGal A5 10 wGal FGL Environmental Environmental errors are highly site dependent and should be modified by only experienced users Recommended values for all environmental uncertainties are 0 0uGal zero unless a user is very knowledgeable about the site in question Set up Set up uncertainties are depending on both the instrument AND the operator For example and experienced operator can set up an 5 with a system error of 1 0uGal An experienced relative meter operator can measure a gradient to 0 03uGal cm Set up errors change according to the instrument and may be increased with respect to the operator Recommended values for modeling uncertainties are System 1 0 uGal FG5 3
26. e screen Select Project Open and navigate to the gSampleData directory Select the file 09 jan 02a fg5 The program environment will now appear as shown in Figure 2 06 Absolute Gravity Data Acquisition and Processing Software The Set data filenames are displayed in the left set view control window Notice that for this example each set is named sequentially in this example 001 through 012 with the project name used as the prefix and as the suffix By default g opens four Views of the data at start up Each view can be enabled by the tab control at the lower part of the window The default windows are 1 Figure 1 Start up screen 06 Absolute Gravity Data Acquisition and Processing Software wi a 4 wi Figure 2 Open project file The State Window The main window g uses to convey information to the user is the State Window The State Window contains four separate sections note that the meaning of each box value can be determined by hovering the mouse cursor over the box until the tool tip appears State 1 Setup Position 40 02885 10504604X 1528 84265 so f System 8 El 1 Drop Project 0124 56 97964728769 2639 oss 100 01002 2
27. ect determines the locked peak by checking the input voltage on the Patch Panel Laser input channel 31 N o Modulation Frequency includes the modulation frequency entered in the System Laser Setup page in the equation of motion This option should always be selected when using a WEO laser g6 Absolute Gravity Data Acquisition and Processing Software e ML I o Alternate instructs the software to alternate between the Blue and Red lock settings of the AL 1 or ML 1 laser It is also possible to select just one mode but this is highly discouraged as it is the average of the two modes that gives the correct gravity value Seismometer If data is taken from an FGL meter enabled with the seismometer option FGLS this box can be checked to apply the seismometer signal The compensated signal is determined by integrating the seismometer velocity and subtracting the result from the trajectory This option is only valid with the FGLS option This option should be used carefully in Real time mode as it takes substantial processing time In general drop rates should be set to 15s or greater if Seismometer Compensation is enabled for Real time acquisition Drop Fit Default parameters for an FG5 A10 FGL are Start Time 35 20 ms Stop Time 200 135 ms Fit Sensitivity As described above Fit Sensitivity allows the user to determine the change in the calculated gravity value as different portions of the drop f
28. ensitivity Statistics Comments Tide Correction Models Berger ETGTAB Potential Filename Tidal Parameters Filename OceanLoad Oceanloading Format Additional Menu Options 24 24 25 26 26 26 26 27 27 27 27 28 28 29 29 29 30 30 30 31 31 21 31 31 32 32 32 32 32 33 33 33 34 34 35 36 37 06 Absolute Gravity Data Acquisition and Processing Software Project New Open Close Save Save as Project Save as Template Edit Reset Time Offset Process Rate Set Break Point Go Step Break Stop Quick Update View Channels Options Output Additional Utilities Convert Additional Utilities gProjectMerge Additional Utilities gProjectCopy License Information Support Maintenance 37 37 37 37 37 37 37 38 38 38 38 38 39 39 39 39 39 39 39 40 41 42 42 43 45 45 45 N Introduction g6 Absolute Gravity Data Acquisition and Processing Software This manual explains the operation of the Micro g LaCoste MGL formerly Micro g Solutions Absolute Gravity Data Acquisition and Processing Software software operates in the Windows environment g can be used with all MGL absolute gravimeters including the FG 5 A 10 FG L gravimeters and is capable of process
29. ew mode Data review when enabled allows users to click on a particular drop or set in the tree view and view the last data that was stored For Data Review mode to work properly this option must be enabled before processing the data Email For system controllers with an internet connection g can be set up to send periodic emails with real time processing results Note that by default email notification is off Figure 22 shows the Email Notification Dialog Box The User must enter an email server a valid identity for that server and a valid recipient Note that any errors encountered are suppressed to avoid interference with data acquisition If enabled the default information provided is Current total project gravity value Current set scatter Gravity value of the last completed set Drop scatter of the last completed set Total project uncertainty The number of the last completed set A copy of the latest version of the project txt file A copy of the latest version of the set txt file The notification can be set for never after every completed set after every other completed set or only at the end of a completed project 40 06 Absolute Gravity Data Acquisition and Processing Software E mail Setup Emdit Server mailservercom 000000000000 From F SGaavipmetetcom 000000000 Te ol Beep Subiect Gavyba 000000000000 Body r Included Data In Body Project Gravity
30. fication that the mean value is consistent with earlier sets See Figure 6 for an example Set Gravity Bee Figure 6 Current Set Value Update A10 example data The first 5 sets are complete 100 drops each and the 6th set is only on drop 3 The mean value of the 6th will approach the established mean and the error bars will decrease as more drops are acquired The Set View Control Window By default g displays the Set View Control Window at start up This window is used to select which sets are to be processed and to set a break point in the processing if necessary The figure below shows a detailed view of the Set View Control Window The check boxes to the left of the Set Filename indicate whether or not the set is included in the processing Sets may be checked or unchecked by placing the mouse cursor directly over the box and clicking the left mouse button 11 N g6 Absolute Gravity Data Acquisition and Processing Software 03 jan 02a001 gsf w 8 Erie 09 jan 028002 gst Erie 09 jan 028003 gst ff Erie 09 jan 028004 gsf Erie 09 jan 028005 gsf v ep E 2 E UnCheckSelected Check Al TE Check Red Deck Blue Set Break Point Clear Break Point Figure 7 Right Mouse Button State View Control Window Optionally if the left mouse button is single clicked over the filename the set is highlighted To highlight mu
31. format of the Ocean Loading file is shown in Figure 19 Users may generate this file using the OceanLoad tool as explained above or from their own data source sn fy OceanLoad Notepad t File Edi Format Help nlOceanLoad Component Amplitude 2 5 1947e 009 109 972 6287e 009 1 471 001 2623e 008 56 350 6027e 009 70 041 5885e 010 168 8528e 009 4179e 010 5102e 009 0648e 010 42 2595e 011 120 393 1 0557e 009 8 944 001 Figure 19 Example Ocean Load File Format 36 N Additional Menu Options g6 Absolute Gravity Data Acquisition and Processing Software Project New This option creates a new project file from scratch All parameters are default and users must change the options according to their setup location instrument and system data acquisition parameters and control parameters This includes the System Factory Height Rubidium Clock Frequency ML 1 Laser Wavelengths for A10 and FGL instruments as determined by Micro g LaCoste and the Laser Modulation frequency as determined by Winters Electro Optics WEO Open This option opens an existing FGS file Close This option close the current FGS file Save This option saves the current 5 file Save as Project This option allows you to save a copy of the current FG5 file to disk marking the file as real time as opposed to Post Mission The current 5 file is closed and the copy is o
32. gravity total uncertainty drop to drop scatter set number number of accepted drops percentage of accepted drops mean tide correction mean ocean loading correction mean polar motion correction mean barometric correction mean datum transfer correction and mean reference Xo correction Project The group of all the sets constitutes a project Summary information about the project including mean time of sets processed set to set scatter total uncertainty mean tide correction mean ocean loading correction mean polar motion correction mean barometric correction mean datum transfer correction and mean reference Xo corrections 06 Absolute Gravity Data Acquisition and Processing Software Drops The Drops view displays individual drops minus the mean value of the set Accepted drops i e those that are within the user selected statistical range are plotted in green while rejected drops are plotted in red The top of the view informs the user of the current set number the current drop number the current drop to drop scatter of the set as well as the number of drops accepted and the number of drops rejected Fit Residuals The Fit Residuals View displays the residual signal the difference between the actual fringe time and the least squares fit estimate of the position at that time With system response disabled Figure 4 the green signal is the residual vector from the current drop while the blue signal represents the
33. he warning Invalid Password File and exits after acknowledgement from the user You are now ready to run g IMPORTANT Due to how the software protection in g works if at any time the user adds or removes hardware from the computer in which g is installed they must obtain a new password file by following the above steps N Post Mission Processing g6 Absolute Gravity Data Acquisition and Processing Software To learn how to process absolute gravity data in post mission after the data has already been collected and archived we will use the sample data included on the distribution disk gSampleData Acquiring data in real time is discussed below g Binary Data Files Structure g maintains a binary project file that contains all the station system acquisition control and comments information used when occupying a absolute gravity station as well as a list of all names of the set files Project files have the project name as the prefix and end in a fg5 extension For example the gSampleData directory contains a project called Erie 09 jan 02a fg5 Raw observation data for each set is stored in a binary gravity set file with extension All raw data including time of drop fringe times and auxiliary sensor s data is stored in this file The files must be accompanied by the corresponding project file in order to be processed by the g software Set files are named sequentially based on the project f
34. he name of their projects This is useful if the user entered the wrong name for a project and needs to change it later Figure 25 shows gProjectCopy 43 06 Absolute Gravity Data Acquisition and Processing Software y Untitled gProjectCopy Figure 25 Project Copy Dialog Box Input File This is the file which the user wants to copy New Project This is the name of the output project name Copy Button This button starts the copying process 44 N License Information Licensed users of g are entitled to three install platforms with the Main License Additional installations including support are purchased one seat at a time directly from Micro g If your institution or company requires g to run on more than three platforms please contact MGL directly or visit our website www microglacoste com for more information g6 Absolute Gravity Data Acquisition and Processing Software Support Questions concerning the operation of g software and any problems using g should be directed to info microglacoste com You can expect to receive an email or phone call within forty eight hours of your inquiry Maintenance Periodically MGS will post an upgrade patch for g on the website These patches will be posted without notification so please check back every few weeks to get the latest patch if applicable 45
35. ile name the number of the set and the extension For example in the gSampleData where the project name is Erie 09 jan 02a fg5 the raw data file for the 5 set is named Erie 09 02a005 gsf The raw data file for the 12 set is named Erie 09 02a012 gsf IMPORTANT When transferring sharing or archiving g data it is necessary to include the Project file fg5 and ALL the set gsf files together The other files txt and project graphs can be recreated by the software and it is technically not necessary to archive those As of g6 it is now possible to Import and Export all the project parameters and raw data in ASCII format Please see the Section on Additional Menu Options for more information How g works g allows users to interactively change and select processing parameters and or sets and drops through standard Windows controls including trees dialog boxes drop down text boxes check boxes and radio buttons If necessary prior to processing a data set the user will select and or modify the appropriate processing parameters and which specific sets and or drops to include in the processing g processes data sequentially That is each set is re processed in the order it was observed If a change is made in the processing parameters it is necessary for all data to be completely reprocessed Starting g To start g double click on the g icon The screen shown in Figure 1 will appear on th
36. ing archived data collected with most Olivia versions after being converted to the g format using the included Convert application The software package provides sophisticated data collection processing and analysis capabilities including standard environmental gravity corrections necessary for uGal gravity measurements The software allows the user to customize the data acquisition program for each site including geodetic coordinates delayed start up set and drop rate and other detailed site information g requires a binary security file that is unique to each individual system to operate g users familiar with previous version of g Olivia or absolute gravity data acquisition will find the software easy to use and operate Those new to absolute gravity measurement should read this operation manual carefully before operating any MGS absolute gravimeter or post processing any absolute gravity data System Requirements 8 relies on both text and graphical output to assist users in quickly evaluating instrument performance and results g runs best with the following minimal standards Operating System Windows 98 2000 NT XP Free Hard Drive Space 1 GB or greater RAM 512 MB or greater Processor Intel P3 or greater Processing Speed 1 GHz or greater N Installing g g6 Absolute Gravity Data Acquisition and Processing Software Licensed users of g will receive one Compact Disc media with at least the following 4 me
37. ing allows users with L Series lasers to acquire data with both laser frequencies in a short time interval and still spread the entire project over a longer time interval For example data can be acquired with the red mode and then a few minutes later with the blue mode Then after an hour the whole red blue sequence can begin again Enable Enables red blue sequencing Red Blue Interval Time interval between the start of a red set and the start of the next blue set typically a few minutes e Sequence Interval Time interval between the start of two red sets An example of Red Blue Sequencing is shown below 30 N g6 Absolute Gravity Data Acquisition and Processing Software E Set Gravity oog Figure 16 Example of Red Blue Sequencing Acquisition Mode Control The following information may be set from the Control Page See Processing Control and Data Corrections for details on these options General Terms e Barometric Pressure applies barometric pressure correction e Polar Motion applies polar motion correction Reference Xo applies reference Xo correction Datum Height applies datum transfer correction Tidal Terms Berger applies standard earth tide correction ETGTAB applies advanced earth tide correction and Ocean load System Response Applies a system response correction See the processing section for more details Laser WEO o Automatic Peak Det
38. is located in the gWavefiles directory The default file contains Tamura s potential Tidal Parameters Filename This file can be supplied by the user or generated on the fly as discussed earlier The format of the file is shown in Figure 18 The default setup for g enabled by checking the Default box is for a dff file generated by the Oceanload Model This setup does NOT contain any ocean loading component If the user has a compatible model or observed tidal parameters for the gravity station the Default button may be unchecked and if applicable the Observed radio button checked Phase Kappa is set to Zero iyi OceanLoad Notepad File Edi Format Help 06 Absolute Gravity Data Acquisition and Processing Software lal x 0 000000 TIDALPARAM 0 002428 TIDALPARAM 0 721500 TIDALPARAM 0 921941 TIDALPARAM 0 989049 TIDALPARAM 0 999853 TIDALPARAM 1 719381 TIDALPARAM 1 923766 TIDALPARAM 1 991787 TIDALPARAM 2 003032 002427 249951 906315 974188 998028 216397 906462 976926 002885 182843 M MEME 000000 160000 154250 154240 149150 134890 161720 161720 161720 161720 0 0000 0 0000 0 0000 0 0000 0 0000 0 0000 0 0000 0 0000 0 0000 0 0000 Figure 18 Example Delta Factor File Format tidal tidal tidal tidal tidal tidal tidal param param param para
39. it are processed By default a few milliseconds around the start time and stop time are plotted Typically the gravity value should be constant within a few uGals Given the nominal fit times above the sensitivity settings for an FG5 A10 FGL should be approximately e Top Start 25 15 ms Top Stop 45 25 ms Bottom Start 195 130 ms Bottom Stop 205 140 ms Statistics This section was discussed above in Processing Control and Gravity Corrections In general it is recommended to accept the g default numbers for the instrument specified Comments Users may enter up to 100 lines of field or processing notes in this section To enter a new line press Ctrl Enter 32 N Tide Correction Models g6 Absolute Gravity Data Acquisition and Processing Software g software accommodates two Tide Correction methods ETGTAB and Berger Within each it is possible to incorporate an Ocean Loading model Most users should use the modern ETGTAB routine but the Berger model is provided for completeness The amplitude and the phase of the gravity loading are computed using the Farrell s method The Green s functions for the PREM model are used and a correction for the mass conservation is included The users may choose different ocean tides models Details of the choices and options are discussed below Berger the Berger correction the tidal parameters set using a constant delta factor of 1 1554 and a
40. ltiple sets highlight one set then use the lt 5 gt key and T or i arrow keys accordingly The right mouse button will bring up the floating menu shown in Figure 4 The following options are available Check Selected Checks all highlighted sets UnCheck Selected Unchecks all highlighted sets Check Checks all sets Check Red Checks all odd numbered sets for use in ML 1 Red Blue Lock Analysis Check Blue Checks all even numbered sets for use in ML 1 Red Blue Lock Analysis Set Break Point Places a Break Point marker by the selected set g will process up to the break point and pause Clear Break Point Clears the breakpoint When reprocessing data for the first time after collecting data and reopening a project it is best to process ALL sets in the project then go back and delete unwanted sets The Process Quick Update option from the main menu can be used to quickly recalculate the mean project gravity value and update the set views if no parameters are changed If any processing parameters are changed g automatically recalculates gravity for the entire data set 12 N Processing Data g6 Absolute Gravity Data Acquisition and Processing Software Reviewing Processing Parameters Processing parameters may be reviewed through the Process Setup screen shown in Figure 8 the user may also press the F3 key to vie the Setup screen All processing parameters are stored in the
41. m param param param param param NOTE An Observed Gravimetric Delta and Kappa Factors File contain the Ocean Loading component and therefore the Oceanloading Filename option is disabled automatically OceanLoad Previous versions of g came with a separate tool for calculating OceanLoading but it is now built into the program Two files are created by the OceanLoad tool Delta Factor File Oceanload dff This ASCII text file contains the listing of start frequency end frequency the Delta factor amplitude and phase in degrees in a format compatible with ETGTAB This file can ONLY be used with the ETGTAB option Ocean Loading File Oceanload olf This ASCII text file contains the ocean load parameters Wave Amplitude and Local Phase listing The file has an olf extension by default and can be used with Berger OR ETGTAB options It is recommended that the base name Oceanload be modified to something unique for the current instrument location With g6 the site name is automatically appended to the basename of Oceanload For example the Oceanload files for site TMGO are named Oceanload TMGO This helps avoid the situation in which the ocean load files for a different location are accidentally used in the calculation resulting in the wrong gravity value g will use the information from the Information page to get all the data that it needs to create the OceanLoading files The
42. mmary File The set summary file contained in goutputl set txt contains set by set information including Set Number Time Day of Year Year Gravity Set Standard Deviation Set 18 N measurement precision Set uncertainty tide correction barometric correction polar motion correction datum transfer correction reference Xo correction temperature pressure auxiliary channels and number of drops accepted and number of drops rejected The file is tab delineated and is easily imported into most spreadsheet programs g6 Absolute Gravity Data Acquisition and Processing Software Additional Window Displays addition to the default displays Tree Control State Drops Sets Fit Residuals g also supplies a variety of views to convey information about processing or data acquisition status A description of each view not previously described follows Set Histogram Displays a histogram of the processed sets general users should expect to see normally distributed data e Set Sensors Displays up to six separate charts Charts 1 5 show the default channels for a Micro g Patch Panel Temperature Super Spring Ion Pump Laser and Barometer The sixth chart is reserved for channels 6 7 and 8 and stacks all three channels onto one graph if enabled Set Corrections Displays six separate charts one for each type of correction applied to the calculated gravity value Tide Ocean Loading Polar Motion Barometric
43. n 6 66uGal Barometric Pressure 2 64uGal Datum Height 91 51uGal Reference Xo 0 01uGal Uncertainties Earth Tide Ocean Load Barometric 1 00uGal Polar Motion 0 05 1 Laser 0 05uGal Clock 0 50 1 System Type 1 10uGal Tidal Swell 0 00 1 Water Table 0 00 1 Unmodeled 0 00 1 System Setup 1 00uGal Gradient 0 91 1 0 03uGal cm 0 50uGal 0 20uGal Comments First Demo Run Which Version of g Which version of 4 processed the data acquired the data Institution Name for reference Operator s Name for reference Station Data Section Station Name Site Code of the Station Position of the station Measured Reference Height Selected Datum Height Site Gradient Nominal Air Pressure at the Site Barometric Admittance Factor Polar Motion Coordinates Instrument Data Section Instrument Type Instrument Serial Number Micro g Determined Factory Height Frequency of the time standard Laser type and serial number Peak and measured voltage Peak and measured voltage Peak and measured voltage Peak and measured voltage Peak and measured voltage Peak and measured voltage Peak and measured voltage Modulation frequency of the laser Processing Results Section Date of gravity Value Time of gravity Value Day of year of gravity value Year of gravity value Absolute value of gravity uGal Set to set scatter uGal Measurement precision u
44. nly In general it is much easier to set a break point from the tree menu Go This option starts the processing in both Post Mission and Real Time Step This option allows users to view process drops step by step in Post Mission mode only Break This option allows user to Pause processing and should only be used in Post Mission mode Stop This option stops all processing in Post Mission processing or Real time data acquisition Quick Update This option is enabled after all sets have been processed If a users wishes to discard Sets to be included in the final determination of the absolute value of gravity after the sets are deselected on the tree Quick Update will update the project number according to the last setup of processing parameters If any processing parameters change Quick Update automatically reprocess all selected sets View Channels This option allows users to view data channels before and after processing This is useful since users sometimes would like to know what data is coming in from channels with out having to process any of the data 39 06 Absolute Gravity Data Acquisition and Processing Software Chea Figure 21 View Channels Live Update Window Options Graphics This option allows users to manually set all scales in the graphs Graphical scales are saved to the project file The user can also enable or disable Data Revi
45. ominal start and stop fit times have been selected the program can also calculate a gravity value for each fringe in a range about both the nominal start and nominal stop of the drop This allows the user to determine how sensitive the final gravity value is to the choice of the fit duration The user can select a window about the nominal start and stop times typically 10 ms and view the sensitivity in View Fit Sensitivity Start Stop Typical sensitivities should be 2 Gal for an FG5 and less than about 10 for an A10 at a quiet site Statistics Drop rejection significance determines which drops are automatically rejected by the software The default value is 3 which means that in a set any drop that 15 more than 3 from the mean is rejected Note that this function is purely statistical there 1s no hardware information used to reject drops g now calculates the total uncertainty for each set and for the final project gravity value The total uncertainty is given by 2 2 On Oss dr stat where 6 is the statistical uncertainty given by the set scatter standard deviation stat divided by the square root of the number of sets One VN stat set set 24 06 Absolute Gravity Data Acquisition and Processing Software and is the total systematic uncertainty which is described below The Statistics Setup button leads to the menu shown in Figure 14 The statistical uncertainty estimate is b
46. pecified height labeled datum entered the site information page Typical gravity datum heights 0 cm 100 or 130 cm often used for FG5s The transfer is calculated by adjusting the gravity value using the difference between the measured reference height plus factory height and the datum height and multiplying the difference by the site gravity gradient Note that term datum has nothing to do with ellipsoid datums Tidal Correction The effect of lunar solar mass attraction is computed and applied to the observations each drop A gravimetric factor usually 1 16 is used to compute the effect of tidal uplift in the continental crust due to the mass attraction of the sun and moon g allows for two types of Tidal Corrections e Berger Originally written by Jon Berger in 1969 and modified by several others throughout the years Originally compiled by the late Georg Wenzel ETGTAB uses a more sophisticated calculation Earth tide models are discussed in more detail below For more information see Niebauer et al A New Generation of Absolute Gravimeter Metrologia 1995 22 N System Response System response is an advanced fitting routine that fits multiple numbers of damped sinusoids to the standard equation of motion Note in most applications it is not necessary to use system response It is designed for field applications in which the measurement surface is hollow or o
47. pened Save as Template This option allows users to write a copy of the current project file to disk marking the file as a These files are usually not edited and the user cannot acquire data with a GTF GTF files are meant to be used for creating new FGS files or other files Export g employs it s own binary format when storing both the header fg5 and set gravity data gsf For archiving and certain analysis purposes g also allows the exporting and importing of ASCII data Real time processing is still carried out using the g format but in replay mode and ASCII version of the data can be created by pressing Export This creates two files that are editable with any plain text editor e lt project name gt fgS txt this file contains all of the project Setup information Information System Acquisition Control and Comments as well as any processing information 37 N e lt project name gt gsf txt this file contains all of raw gravity data for all of the sets raw fringe times for every drop and the associated analog sensor data g6 Absolute Gravity Data Acquisition and Processing Software Import To import ASCI I data it must be in the format identical to that created by the Export function you must first create a New Project Then select Import and you will be prompted to enter the lt project name gt fg5 txt file name Note that there must be a corresponding lt project name gt
48. processing the data Processing can be started three ways 1 The user may select Go from the Process menu 2 The user may push the blue button 3 The user may press 5 After starting either option 1 or 2 above in post mission processing g will prompt the user whether or not to overwrite the current existing Project and Set summary files 2 creates two output ASCII text files by default the Project Summary and Set Summary File default the files are named project name gt project txt and lt project name gt set txt In some cases users will want to change the names of the output files to preserve prior processing results For details of the ASCII output file structure and contents see Appendix 2 ASCII Output Files Let s select and enter our own default base name goutputl By default then g will create two ASCII text files goutputl project txt and goutputl set txt After pressing the OK button g will begin processing the data Selecting Yes would simply overwrite the lt project name gt project txt and project name gt set txt files 14 N Processing Status With the default windows displayed State Drops Sets and Fit Residuals the user is able to quickly evaluate the status of data processing In the figures below we have set a break point at Set 3 to pause the processing The screen in Figure 9 is captured immediately following the last processed drop of
49. r this information from a pre created file Convert Button use this feature to convert Degree Minutes Second DMS coordinates or Universal Transverse Mercator UTM coordinates to decimal degrees DD System System The following parameters may be set from the System Page Instrument Instrument Type Select FG5 A10 or FGL Certain options are enabled or disabled according to the instrument selection S N Enter the serial number for note keeping purposes e IF Type Select the interferometer type for note keeping purposes Laser Type Select the laser type and parameters associated with the laser o Laser Voltage and Serial Number Enter the 1F voltages for each peak d g it is not necessary to enter values for h j if the measurement begins with d g selected The software will use this voltage to determine the laser peak in use Please refer to the Instrument operator s manual for more information o ML l Blue and Red Lock wavelength and Warm up Mode Refer to the information provided with your instrument for the wavelength values Do not change these values unless told to do so this will directly affect the calculated gravity value Warm up mode should typically be about 40 seconds this refers to the amount of time before data acquisition that the laser enters lock mode Enter the serial number for note keeping purposes 27 N Seismometer FGL Only Seismometer Type
50. sound from the computer s speaker NOTE the beeps do not sound from an installed sound card but ONLY the computer s local speaker and when the bottom message window indicates Finished For our example the final gravity value is 979647292 67uGal with a set scatter of 2 26uGal and a total uncertainty of 2 24uGal Reviewing Processing Results Remember when we changed the output name to goutputl If we use Windows Explorer to navigate to the gSampleData directory we will see two new files goutputl project txt and goutputl set txt These files are ASCII text and can be opened with any text editor Project Summary File The project summary file is designed to be a snapshot of the acquisition and data processing It is intended to serve as the primary resource for archiving absolute gravity data The project summary file is reproduced below in Figure 11 Explanations of each line are included in the figure but are NOT normally part of the output file The output data 15 divided into related sections File creation and Header Information Station Information Instrument Data Processing Results Gravity Corrections Uncertainties and 17 06 Absolute Gravity Data Acquisition and Processing Software Comments sections ma goutputi project with annotations Notepad File Edit Format Help Depending on the options selected Laser Tide Model Ocean Loading include additional information
51. st six channels All values are listed in Volts and correspond to the standard patch panel configuration on all Micro g instruments g6 Absolute Gravity Data Acquisition and Processing Software The third box Set contains information pertaining to the current set being processed In the case of Figure 10 it is Set 2 The average time of the accepted drops used to calculate the set mean is displayed 01 16 33 the average corrected gravity value 979647288 94 the uncertainty of the set in uGal 2 33 the drop to drop scatter Gal 9 19 the set number 2 and the number of drops accepted 97 The next six boxes display the average value of the corrections applied in uGal tide 18 ocean loading 0 00 polar motion 6 66 barometric 1 71 datum transfer 91 51 and reference Xo 0 01 The final box Project contains information pertaining to the current state of the project through the last processed set In this case Set 2 The average time of the sets is shown 00 46 41 the day of the year and last two digits of the current year 01002 implies the tenth day of the year 2002 the number of sets processed 2 the average corrected gravity 979647289 79 the set to set scatter in Gal 0 94 the set uncertainty in Gal 2 13 and the average applied corrections in uGal To restart the processing press 5 or select Go from the Process menu Processing Finished Processing is complete when the two beeps
52. therwise unstable In laboratory or stable pier type situations it will not be necessary to use System Response Because System Response can mask a problem with the site by flattening out a residual signal that would otherwise indicate a problem it is recommended to only use System Response in Replay mode Frequency Response Setup 63 Max Number of Terms Significance Threshold N 07 06 Absolute Gravity Data Acquisition and Processing Software Minimum Frequency Hz 15 Figure 13 System Response Setup Dialog Box To apply System Response check the box and press the Setup button The menu shown in Figure 9 to the right will appear It is recommended to accept the default values of 3 terms 20 significance threshold and 15 Hz When System Response is enabled it is possible to view the Power Spectral Density of the Residual Signal Laser Control The software is designed to function with three different laser types For WEO 100 lasers the user can select Automatic Peak Detection g uses the measured voltage on Channel 4 to determine which peak DEFG or GHI was valid during the drop If for some reason the voltage in channel 4 is invalid the user can still deselect Automatic Peak Detection and manually enter the wavelength from the pull down menu The wavelength modulation check box is only valid for WEO 100 lasers and it is recommended that the box always be selected Refer to the WEO manual for discussion
53. up The Advanced button and details of System setup are discussed in Real time Data Processing 13 N e Acquisition This menu control how the instrument collects data The user can set the number of sets to collect number of drop per set start time immediate or delayed drop interval set interval and pulse delay the time between the drop and the next lift These options are cannot be edited in post mission mode and are discussed in Real time Data Processing e Control This information controls how the software processes the data The user can enable barometric pressure corrections polar motion corrections reference Xo correction and datum height to be applied to the data The user may select tidal terms to be either Berger or ETGTAB whether or not to apply system response laser mode Automatic Peak detection in the case of a WEO 100 laser or Red Blue alternate in the case of an AL 1 or ML 1 fit for wavelength modulation WEO 100only starting fringe from which to begin processing number of fringes to process and statistical parameters These items are covered in more detail in Processing Gravity Data e Comments Users may enter up to 100 lines of field or processing notes in this section 06 Absolute Gravity Data Acquisition and Processing Software For now we will NOT change any processing parameters on the sample project Start Processing Once g is setup according to user set parameters it is ready to begin
54. values it uses are Name Site name for the g project file Latitude Latitude of the site Longitude Longitude of the site Elevation Mean Sea Level elevation for the site 35 N The ocean tide files are supplied to Micro g by Dr Olivier Francis http www ecgs lu g6 Absolute Gravity Data Acquisition and Processing Software Advanced Users Setup allows the selection of three common ocean tide model for each term e Schwiderski FES2004 e CSR3 0 Users unfamiliar with these wave file models should accept the default values Note that the FES2004 model is considered state of the art but due to the high resolution of the model it can take a few minutes to calculate the ocean load For quick setup purposes the default model is still that of Schwiderski g allows users to use already existing OceanLoad files or it can dynamically create the necessary files that the user specifies on the fly To use existing files enable OceanLoad by clicking the check box in the Setup option and then search for the specified olf and dff files Or to dynamically create the files enable OceanLoading and then pick an base name for the OceanLoad files Then when g is run for the first time it will ask to create the specified files Oceanloading Format As discussed above depending on the information modeled versus observed contained in the tidal parameters file an Ocean Loading file may or may not be entered The
Download Pdf Manuals
Related Search