GAMIT step-by-step baseline calculation
In the recent elective courses, I will study gamit, and I will share my learning process with you. I hope it will be helpful to everyone.
System used: Ubuntu20.04 + GAMIT10.71
The data used in this internship is the observation data of 4 IGS stations (bjfs, lhaz, urum, ccj2) on April 5, 2018, with an annual accumulation of 095.
Note: The file naming format in this chapter is named after the actual data of this project, and it should be modified according to the actual situation during the actual calculation.
1. Data preparation
The data is downloaded from the IGS Data Center of Wuhan University, the address is as follows:
http://www.igs.gnsswhu.cn/index.php/home/data_product/igs.html
Create a project folder:
This article is work (it can also be named after the year, such as: 2018):
The file organization is as follows
· work/
—— 095/
—— brdc/
—— igs/
—— rinex/
—— tables/
The tables folder is a linked folder
The link command is as follows (the command is executed under the project folder work):
sh_setup -yr 2018 -doy 095
Put the downloaded data into the relevant folder. The brdc folder stores the broadcast ephemeris file (suffix: .18n), the igs folder stores the precision ephemeris file (suffix: .sp3), and the rinex folder stores the observation data file ( Suffix: .18o).
Two, parameter configuration
Table file update
The table file update is more complicated and error-prone, so it is recommended to find a more detailed table update tutorial for this step.
The following mainly talk about the broken link situation I encountered, and check the link situation by running the following command :
ls -al
If there is a red chain other than the red chain above, you need to find and relink it.
Specific method: by viewing the file address of the following link, viewing its file attributes for further tracking, and finally find the final file, if the final file pointed to does not exist, the file needs to be downloaded.
For the observation data on April 5, 2018 in this article, in particular, carefully check the following documents:
soltab.2018.J2000, luntab.2018.J2000, vmf1grd.2018 (related to map.grid), otl_FES2004.grid (related to otl.grid), atmdisp_cm.2018 (related to atml.grid) and nutabl.2018.
The table file can be downloaded at the following website
http://sopac.ucsd.edu/GAMIT.shtml
ftp://garner.ucsd.edu/archive/garner/gamit/tables
You can also update the table with the following command:
gftp <网址>
Parameter configuration
There are two files sestbl. and sittbl. in the tbles folder
Sittbl. file setting : sittbl. can constrain the site, and set a strong constraint on the known coordinates of high precision, which can be set to 5cm; to loosely constrain the coordinates of the point to be sought, this article sets it to 100m.
As follows:
The corresponding position in the sestbl. file can be modified as follows:
Use otl.list = Y ; Ocean tidal loading list file from OSO
Use otl.grid = N ; Ocean tidal loading grid file, GAMIT-format converted from OSO
This is the configuration of the ocean tide correction file required in the baseline calculation. There are more detailed parameter settings, please read the relevant documents carefully.
Because what is processed here is the observation data of the IGS station, according to the above modification, you can directly use otl.list.
Initial file generation
Generate station.info
Enter the tables folder and use the following command
sh_upd_stnfo -files ../rinex/*o
Generate a new station.info file with the following content:
Generate lfile.
The lfile. file contains the rough coordinates of the station, and the method of generation is as follows:
Execute in the rinex directory of the working directory:
grep POSITION *.18o > lfile.rnx
rx2apr lfile.rnx 2018 095
gapr_to_l lfile.rnx.apr lfile. '''' 2018 095
The contents of the lfile. file are as follows:
Then copy the lfile. file to the tables file.
Three, start to solve
First create a year-end-date folder (named 095 in this article), and link it with the igs, brdc, rinex, and tables folders
Enter the 095 folder and execute the following commands:
ln -s ../igs/*sp3 ./
ln -s ../brdc/*n ./
ln -s ../rinex/*o ./
ln -s ../tables/* ./
Let's start the distribution solution:
Note: All commands are executed in the 095 folder
1. Execute sh_makexp
The command is as follows:
sh_makexp -expt test -orbt igsf -yr 2018 -doy 095 -sess 99 -nav brdc0950.18n -sp3file igs19954.sp3 -jclock sp3 -apr lfile. -sinfo 30 0 0 2880
The normal end is as follows:
2. Generate G-file (track file):
The command is as follows:
sh_sp3fit -f igs19954.sp3 -o igsf -d 2018 095
After success, file check:
$ sh_check_sess -sess 095 -type gfile -file gigsf8.095
At this time, there may be an error saying that the gigsf file could not be found. Check the 095 folder and find that the name of the generated G-file is gigsg8.095. Change it to gigsf8.095. Check again and pass the check.
3. Generate J-file:
The command is as follows:
makej brdc0500.16n jigsf8.095
File check after success:
sh_check_sess -sess 095 -type jfile -file jigsf8.095
4. Generate X-file:
The command to generate a double-difference observation file is:
makex test.makex.batch
The successful screenshot is as follows:
5. Generate script:
Run the fixdrv command
fixdrv dwork8.095
Note: The following errors may appear at this time
Solution: Delete the GAMIT.fatal file in the 095 folder
A screenshot of the successful command is as follows:
6. Finally, perform data calculation
csh bwork8.bat
Wait for the data calculation to complete.
The screenshot of the successful solution is as follows:
Related results
After the solution is successful, there will be O-file, Q-file and H-file in the 095 folder, as well as the updated station coordinate lfilg. file.
Errors in the solution process can be viewed in the GAMIT.fatal file.
So far, the process runs smoothly, but the settings of the processing command parameters and the related file parameters and the meaning of such settings require further reading of relevant literature for learning.