Atmospheric Correction for InSAR

[Shadi1]

Should I request GACOS’s ztd maps in binary grid format instead of Geotiff format so that they can be implemented into matlab together with the unwrapped phase?

I am having problems on how to apply the GACOS atmospheric correction with StaMPS. The unwrapped interferograms are produced in formats only readable by matlab and they only contain PS pixels and not exactly “Raw Interferograms” as what (Yu, C., Li, Z., & Penna, N. T. (2020)) have described in their model. So if there’s a tutorial that can guide into step by step for such a purpose, would be an outstanding initiative

[Shadi1]

Have you used the GACOS utility before? I have downloaded the ztd maps in binary grid format for each date of the sentinel 1 acquisitions and have downloaded the matlab codes to use them but I still can’t figure out how to apply them

[Shadi1]

@Tereza_S

I wonder if you know of any reason why the linear correction would introduce this however. I have not been able to find anything in literature.

Maybe because of aps_config.sh that is dependent on get_modis.py script.
See this Tropospheric correction for PSInSAR time series - Earthdata Forum

[yzxtll]

@ABraun :thanks for your patient answer until now ,could you tell me how can I know stamps(8,8) running correctly

It seems correct about step 8!,but when I run ps_plot(‘v-dao’),failed

[ABraun]

I haven’t used TRAIN with StaMPS so far, sorry. Some general remarks are given here.

[Shadi1]

How are you able to remove the Atmospheric Artifacts from the LOS displacement map? which software have you been using instead of TRAIN, if you wouldn’t mind sharing?

[ifa43]

Hi everyone, I am gonna sharing my recent finding with TRAIN using GACOS data. I found command “Not enough GACOS data to compute interferometric delays…”, while I’ve been trying to download GACOS data. Regarding this command, please give me some idea so I can continue the process. Thank you

[DeliciousQ]

Hi, I met the same situation as yours, and now I have solved this question.
It is because when downloading the GACOS data it should be in binary grid output format instead of geotiff.
Hope it can help.

[suat]

Hi @ DeliciousQ, @ifa43
I tried to run gacos corection but i took this error. How to set lamda and heading in parms_aps? I cant see any parms about this options in setparam_aps lists.

Best

aps_weather_model(‘gacos’,1,3)
Step 1: Order and Download GACOS data files
You need to download GACOS data from the website, use GACOS_download_info.txt for relevant information
Step 2: Compute the GACOS tropospheric (zenith) delay for individual dates
GACOS delays as downloaded are already Zenith delays, do not need to do anything here
Set lambda manual in parms_aps!
Set heading manual in parms_aps!
Set lambda manual in parms_aps!
Set heading manual in parms_aps!
Set lambda manual in parms_aps!
Set heading manual in parms_aps!
Set lambda manual in parms_aps!
Set heading manual in parms_aps!
Index exceeds matrix dimensions.
Error in aps_gacos_files (line 58)
time = str2num(UTC_sat(1:2)) + str2num(UTC_sat(4:5))/60;
Error in aps_weather_model (line 116)
aps_gacos_files(-1);

[DeliciousQ]

Hi, I had the same problem and solved it by importing the missing parameter from parms.mat.

load('parms.mat')
save('parms_aps.mat','heading', 'lambda','-append')

Also, don’t forget to set the ‘gacos_datapath’ and ‘UTC_sat’.

Parameters can be checked using

getparm_aps

[suat]

Thank you for quick replay. I load heading, lambda and gacos path . But i wonder what is your advice UTC_sat param value and what is refer it?

[DeliciousQ]

It is the same with the time of interest when downloading GACOS data.

It refers to SAR imaging time. For example, sentinel-1 data imaging time is already in the file name.

In my case I set ‘UTC_sat’ as ‘21:49’.
I haven’t use other data and not sure about other data format.

Hope it can help.

[suat]

Its done. I applied gacos correction for my PS points. Thank you for assist.

Suat
Best

[DD-ZHAO]

Hello, eaveryone, before I did the atmospheric correction with gacos, I appended the parameters heading and lambda to parms_aps.mat and manually set heading to the heading angle of the image I was using and lambda to 0.0555. Once the settings were done, the atmospheric correction was done using aps_weather_model(’ gacos’,1,3) to complete the atmospheric correction. Before starting the step6 of phase unwraping, set the parameters setparm(‘tropo’,‘a_gacos’) and setparm(‘subtr_tropo’,‘y’), and execute the command stamps(6,7), and the phase unwraping is successfully completed, but the following error occurs in the step7.

What can I do to solve this problem, thank you very much for your help!