Running GAMIT: Determining loosely constrained GPS positions (Page 2 of 3)

by Andrew Newman

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Please refer to the GAMIT manual (local version) for details of processing.

RUNNING GAMIT: Determining loosely constrained GPS positions

    CAUTION!!!

    PLEASE MAKE A BACKUP OF YOUR ENTIRE RUN DIRECTORY BEFORE RUNNING GAMIT!!!
     % cd ~/MGM   # make sure you are in the correct directory
 % cp -a Socorro2002 prerun  # will create a backup of your directory as prerun
 % tar czvf prerun.tgz prerun

  • We can use an automated script called 'sh_gamit' to run the actual data reduction. Note, that this is another shell script that tries to do all of the necessary processing. 
     % cd ~/MGM/Socorro2002/  # make sure you are in the correct directory
 % sh_gamit               # running sh_gammit with no options give an extensive usage screen
 % sh_gamit -s 2002 311 311 -orbit IGSF -expt smb1 &> sh_gamit311.log & 
 % tail -f sh_gamit311.log    # this will show what is happening on screen
 #   Use CNTRL^c to stop this if necessary (e.g. after a FATAL error)
    Processing finishes normally in about 10 minutes for 1 day, but this is dependent on how many people are working on the machine.

Checking GAMIT output:

  • Once finished, there should be an output file called sh_gamit_311.summary in the 311 directory. Look in this file to determine if run was good.
    Specifically you should look for (highlighted in red in the below screen):
    • The average RMS for individual and all sites should generally be less than about 8.
    • The postfit nrms should be around 0.2 or less
    • Some stations may have their position updated in the lfile. If adjustments are >~1m then the day should be rerun. Remember 1 m in apriori location gives about 1mm in final location error 
    Input options -s 2002 311 311 -orbit IGSF -expt smb1

Processing 2002 311 GPS week 1191 4 Using node: tsunami Started at: 06_09_20_18:28:29

Processing directory: /home/anewman/MGM/test2/prerun/311
Disk Usage:  1458.76  Free  2.08314e+06 Mbyte. Used 1%

Number of stations used 6 Total xfiles 6
Postfit RMS rms, to and by satellite
RMS  IT Site   All  01  02  03  04  05  06  07  08  09  10  11  13  14  15  17  18  20  22  23  24  25  26  27  28  29  30  3
RMS  18 ALL    5.0  47  48  54  49  48  50  45  43  58  53  58  50  50  47  44  45  51  39  53  49  52  47  44  52  50  62  5
Best and Worst two sites:
RMS  18 SVRK   3.9   0   3   4   3   4   4   4   3   4   3   5   4   4   4   3   3   4   0   4   4   5   4   4   4   5   5
RMS  18 MDO1   4.1   4   4   5   4   4   4   5   4   4   4   5   4   3   3   4   4   4   3   5   4   4   4   4   5   4   4
RMS  18 AMC2   5.9   5   6   6   5   5   6   5   6   6   6   7   5   6   6   6   6   6   0   6   6   7   6   5   6   6   6
RMS  18 NLIB   6.3   5   6   8   6   6   6   5   4   8   8   8   7   6   5   5   6   6   5   7   6   5   6   5   7   5   9

Double difference statistics
 Prefit nrms:  0.17701E+03    Postfit nrms: 0.20410E+00
 Prefit nrms:  0.17684E+03    Postfit nrms: 0.20480E+00
 Prefit nrms:  0.17701E+03    Postfit nrms: 0.19302E+00
 Prefit nrms:  0.17684E+03    Postfit nrms: 0.19346E+00
 Number of double differences:  17870

 Numbers of WL and NL Biases 254 Number Fixed: 34


List of sites updated in the tables lfile. based on adjustments to coordinates in the Prefit Solution
SVRK GEOC LONG  -0.7094
SVRK RADIUS     2.1097
  • A copy of this file is also sent to your local mailbox upon completion of sh_gamit. I hope to have pine installed soon. Otherwise you can use mail to look at your local mail.

Failure:

  • If you cannot find the sh_gamit_311.summary file, and it wasn't mailed to you, then GAMIT failed!
  • Look in 311 for files that end with .fatal. Also, the original logfile sh_gamit311.log should give you the error.
  • Unfortunately, the error information that you find, may not be as helpful as you would like. If the program fails and you cannot figure it out from the error files, then carefully recheck the three table files:
    • lfile.
    • sites.defaults
    • station.info
    Be sure that:
    • you have the letter 'O' for MDO1, and the number '0' for SC01.
    • sites.defaults has lowercase station names for the ones being ftp'd (fixed from class).
    • SC01 has an intial position in lfile.
    • you have removed all reference to campaign site ROCK. The lfile. should have a continuous station named ROCK that you do not need to worry about.
    • Make sure that pertinent information in the tables start with a blank space. Many of the gamit programs use this convention to denote that this line is not a comment. In other words, if the first space in a table file has a character or even a tab, the line may not be read by some, or all programs.

Complete 2002 campaign:

  • If you have been successful at running gamit for day 311, then go ahead and run it for days 312,313, 318,319, 323 and 324. These are the days that we had campaign stations operational.

Process 2003 and 2004 campaigns:

  • Just follow these instructions but creating new subdirectories under MGM called Socorro2003 and Socorro2004.
  • You can use the same station.info, lfile. and sites.defaults information for the campaign data (local sites), however you will need to check to see if there continuous sites have different information for the new periods.
  • Data are also in ~anewman/MGM/TEST/
  • Note that in 2004 there were 4 additional stations (one of which ran the entire time!).
  • The days of the campaigns will vary. Please note the occupation days on the raw file names.
  • For a few days new station PAS1 was started and stopped so that there are more than one file with the same doy name. In order to use both files for the day you will need to run teqc manually on the day. This will need to be done for DOY 309, 314, 322
    For example: 
       % teqc -tr d -week 2004:309 +nav PAS13090.nav ../RAW/PAS1309?.dat > PAS13090.04o
   % teqc +qc -week 2004:309 -O.int 30 PAS13090.04o > PAS13090.qc

Some Important Datafiles and results:

    Once a day has been run numerous files are created. The list is too great to be included here, so please refer to the GAMIT manual for detailed information. A useful list of types of files is in appendix 1.

    Of these files, two of the most useful files include:
    • O-file: full position output file
    • H-file: full set of covarience matrices

    Please look through these files for 1 to 2 days to get a better handle on what type of information is in there. Example file names are osmb1a.319 and hsmb1a.04319.

  • We can additionally look at plots of daily positions relative to other sites (baselines) to determine if there are any problems with individual runs for a particular year. The following program does not work correctly across year boundaries. 
    # this created a bunch of files starting with psgamit*
% sh_gamit_baseline -o 3??/osmb1a.* -frame 1 -anot 5
% gs psgamit* # view output using 'gs'.  Use quit to get out
  • One page of sample output is here.
  • Running in this way will create numerous files (59 in 2004) and not all are necessary. Instead, we can run baselines for all stations relative to just one continuous station. This can be done by either creating a file with all the necessary baselines (I haven't tried this yet) or by running individual files using a script. An example of two pairs of baselins is run is below (show 2 baseline sets per page).
  • I will leave it to you to create baselines for all stations relative to a continuous site. PIE1 may be a good choice since it is near by, but not within the magma body. Note that you need to pair baselines with the station that appears first alphabetically first. Hence, if you pick station PIE1, some of your baselines will be ????_PIE1 while other will be PIE1_???? 
    % sh_gamit_baseline -o 3??/osmb1a.* -b CLIF_PIE1  PIE1_VVRS -frame 1 -anot 5  -a CLIF_VVRS # Note the order

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