GAMIT - A WORKING RECIPE ecalais@purdue.edu Gamit/Globk version 10.01 - 2005/04/20 OBJECTIVE: calculate position of site WLCI using 3 IGS stations USNO, NLIB, and AMC2 ############################################## # PART 1: PREPARE FILES IN WORKING DIRECTORY # ############################################## # CREATE A WORKING DIRECTORY #--------------------------- mkdir ~/010 # GO TO YOUR WORKING DIRECTORY #----------------------------- cd ~/010 # COPY YOUR DATA FILES TO YOUR WORKING DIRECTORY AND CONVERT TO RINEX FORMAT #--------------------------------------------------------------------------- For instance, if your files are stored in /my_disk/data_directory/010 in Hatanaka compressed format: cp /my_disk/data_directory/010/????0100.03d.Z . uncompress *Z crx2rnx ????0100.03d rm *.03d # CHOOSE IGS FILES FOR TIE TO ITRF #--------------------------------- http://igscb.jpl.nasa.gov/ Go to "tracking network" and choose 3 to 10 IGS sites well defined in ITRF2000, that define a good network encompassing your local array. # GET IGS DATA FILES #------------------- ftp lox.ucsd.edu [anonymous] cd /pub/rinex/2003/010 bin get nlib0100.03d.Z get usno0100.03d.Z get amc20100.03d.Z quit # GET CORS DATA FILES #-------------------- ftp ftp.ngs.noaa.gov [anonymous] cd /cors/rinex/2003/010/wlci bin get wlci0100.03d.Z quit (actually, WLCI can also be found on lox) # UNCOMPRESS AND CONVERT DATA FILES TO RINEX FORMAT #-------------------------------------------------- uncompress *Z crx2rnx nlib0100.03d crx2rnx usno0100.03d crx2rnx amc20100.03d crx2rnx wlci0100.03d rm *.03d # GET EPHEMERIDES FILE, THEN UNCOMPRESS AND CHANGE NAME #------------------------------------------------------ ftp lox.ucsd.edu [anonymous] cd /pub/rinex/2003/010 bin get auto0100.03n.Z quit uncompress auto0100.03n.Z mv auto0100.03n epgga3.010 # GET PRECISE IGS ORBIT, UNCOMPRESS #---------------------------------- gweek 010 2003 [answer = 1200 5] OR doy 2003 010 ftp igscb.jpl.nasa.gov [anonymous] cd igscb/product cd 1200 bin get igs12005.sp3.Z quit uncompress igs12005.sp3.Z # LINK TABLES #------------ link_tables 2003 /usr/local/geodesy/mit/tables # PREPARE L-FILE (A PRIORI SITE POSITIONS) #----------------------------------------- Calculate precise position from ITRF file, using velocity: gapr_to_l /usr/local/geodesy/process/gamit_setup/itrf00.apr ltmp "" 2003 010 OR gapr_to_l /usr/local/geodesy/process/gamit_setup/itrf2000_2001_rfwg ltmp "" 2003 010 THEN grep USNO ltmp >! ltest3.010 grep WLCI ltmp >> ltest3.010 grep AMC2 ltmp >> ltest3.010 grep NLIB ltmp >> ltest3.010 rm ltmp If a station is not in the ITRF a priori file, then use its approximate coordinates from the rinex file header and transform them to spherical with 'tform'. Alternate options: compute approximate coordinates using RINEX pseudoranges: - use teqc +qc rinex_file - use sh_rx2apr (type `sh_rx2apr` for help) Edit ltest3.010: add one line at the top of the file, for instance 'Epoch 2003.0247: From file itrf00.apr' # PREPARE STATION.INFO (ANTENNA HEIGHTS, EQUIPMENT TYPE) #------------------------------------------------------- grep USNO gt/station.info >! station.info grep WLCI gt/station.info >> station.info grep AMC2 gt/station.info >> station.info grep NLIB gt/station.info >> station.info Edit station.info: - add info for sites not present in station.info - use rcvant.dat to find receiver and antenna code - add first line: test pgga - add second line, a format statement: (A1,2(A4,1X),A16,F7.4,2(1X,F8.4),2(1X,A6),1x,a5,1X,F5.2,1X,I4,1X,I3,1x,I2,6(1X,I2)) - add third line: *SITE Station Name Session Start Session Stop Ant Ht HtCod Ant N Ant E Receiver Type Vers SwVer Receiver SN Antenna Type Dome Antenna SN # PREPARE SITTBL. (SITE SPECIFIC PROCESSING PARAMETERS) #------------------------------------------------------ grep NLIB gt/sittbl. > sittbl. grep AMC2 gt/sittbl. >> sittbl. grep WLCI gt/sittbl. >> sittbl. grep USNO gt/sittbl. >> sittbl. Edit sittbl.: - add info for sites not present in sittbl. - add two lines at the top: line 1: SITE FIX WFILE --COORD.CONSTR.-- --EPOCH-- CUTOFF APHS CLK KLOCK CLKFT DZEN WZEN DMAP WMAP ---MET. VALUE---- NZEN ZCNSTR ZENVAR ZENTAU line 2: << MY SITES >> - IMPORTANT: decide on a priori constraints for your sites. For instance, use 99.99/99.99/99.99 for your local sites (WLCI) and 0.005/0.005/0.050 for the IGS sites (NEU, meters). - set the number of zenith delays to be estimated to 7. # PREPARE SESTBL. (PROCESSING PAREMETERS) #---------------------------------------- cp /usr/local/geodesy/process/gamit_setup/sestbl. . Edit sestbl. as necessary for your experiment. ############################# # PART 2: PREPARE GAMIT RUN # ############################# # FIRST, PREPARE SESSION #----------------------- makexp test pgga epgga3.010 2003 010 3 ltest3.010 30 00 00 2880 # THEN, PREPARE ORBIT FILE WITH PARTIAL DERIVATIVES #-------------------------------------------------- sh_sp3fit -f igs12005.sp3 -o pgga sh_check_sess -sess 010 -type gfile -file gpgga3.010 # PREPARE SATELLITE CLOCK FILES #------------------------------ makej epgga3.010 jpgga3.010 sh_check_sess -sess 010 -type jfile -file jpgga3.010 # CONVERT RINEX FILES TO X-FILES #------------------------------- makex test.makex.batch > /dev/null # PREPARE GAMIT BATCH FILE #------------------------- fixdrv dtest3.010 ##################### # PART 3: RUN GAMIT # ##################### In the foreground: csh btest3.bat In the background: csh btest3.bat > /dev/null & ############################################### # PART 4: EVALUATE THE QUALITY OF THE RESULTS # ############################################### grep "Postfit nrms" qtesta.010 => the postfit rms should be less than 0.5 Edit output file 'qtesta.010' and verify that adjustments and their formal uncertainties (only provided for the two constrained solutions) are small (sub-centimeter). ######################### # ADDITIONAL RESSOURCES # ######################### http://www-gpsg.mit.edu/~simon/gtgk/ --> Gamit-Globk homepage at MIT http://www.seismo.berkeley.edu/~battag/GAMITwrkshp/wrkshp.html --> Gamit/Globk tutorial http://sopac.ucsd.edu/processing/gamit/ --> GAMIT setup files from SOPAC