COSMO Skymed data in stamps

[陈宇]

Hello everyone,

I am working with stamps SBAS using COSMO skymed data.

 does anyone know how to chose the sb_find parameters? like the maxi baseline and the maxi day?

the critical baseline for CSK is around 5450 m. the maxi baseline in my dataset is 1600m.

Thank you very much!

Yu CHEN

[David Bekaert]

Hi,

The sb_find parameters are best limited based such you do not have a fully decorrelated interferogram.

So for the perpendicular baseline, you should not make it larger than the critical baseline.

The critical temporal baseline is often depending on the region, but i guess you could try like a year or 1.5 years.

You can always drop interferograms along the way when you do the PS or SB point slection.

Cheers,

David

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[陈宇]

Hi David,

Thanks a lot for your reply. 

according your advice I guess I could count all pairs in since the maxi temporal baseline is one year in my case. I'll see if they were good during the SB processe. Thanks!

cheers

Yu

[spinorbit]

Hi Yu

COSMO-SkyMed has an average repeat time of 4 days (each satellite has a repeat cycle of 16 days). If you have a dense acquisition plan over your area I usually use 150-250 m as perpendicular baseline and 32 days as temporal baseline. this is valid when dealing with a dense time-series (ie. each satellite acquire over the area).

 If your dataset has been acquired with only one satellite I would generate all interferograms below 300-350 m of perpendicular baseline and 64 days of temporal baseline.

Ciao

Pietro

[陈宇]

Hi Pietro,

Thank you for your advice!

my dataset contains 20 acquisitions of one SWATH. the first 15 acquisitions have a time interval of 16 days. the last 5 qcquisitions too.  but the interval between the 15th and the 16th is 48 days. 

do you think it's suitable to use 350m and 64 days as baselines?

Thanks a lot 

cheers

Yu

[spinorbit]

I think it should be appropriate using those values within the 2 main sets.

Then try to link "manually" the 2 main sets choosing pairs with small baseline.

You can make a Bperp - Btemp plot an choose empirically some links within your interferogram network.

Ciao

Pietro

[陈宇]

Hi Pietro,

I'll try that, Thank you very much!

cheers

Yu

[陈宇]

Hi Pietro,

I would like to ask a quetion about ps_select.m

I use cosmo skeymed data for small baseline. there was 0 PS selected in whole image when i run stamps(3,3). the messages are below. I tried to raise the density_rand to 5, 10, and 20. but same problem happened. 

Have you had a problem like this?

GETPARM: slc_osf=1 

GETPARM: clap_alpha=1 

GETPARM: clap_beta=0.3 

GETPARM: clap_win=32 

GETPARM: select_method='DENSITY'

GETPARM: density_rand=2 

GETPARM: gamma_stdev_reject=0 

GETPARM: small_baseline_flag='y'

GETPARM: drop_ifg_index= 

PS_SELECT: Initial gamma threshold: 1.000 at D_A=0.02 to 1.000 at D_A=0.60

PS_SELECT: 0 PS selected initially

PS_SELECT: Reestimation gamma threshold: 1.000 at D_A=0.02 to 1.000 at D_A=0.60

PS_SELECT: 0 ps selected after re-estimation of coherence

PS_SELECT: Finished

Thank you very much

all the best

Yu CHEN

[spinorbit]

Hi Yu

Did you check if all your interferograms are well aligned ? (i.e.. check if the coregistration step failed somewhere ) .

Did you use fine coregistration parameters suited for the x-band? ( http://osmanoglu.org/sar/80-doris-fine-correlation-parameters ) 

Also try to check at the beginning of the DORIS crop step. When you include lat and lon check if cropped SLCs look consistent (i.e. you cropped the same area ). DORIS may have a bug cause sometimes it crops different areas.

If your test site is a rural area there could not be PS at all.

This is what came up in my mind. I do not use STamPS since a while so maybe the developer team may give a better response to this issue.

Good luck with your CSK processing ! 

Pietro

[陈宇]

Hi Pietro,

I really appreciate your reply. thank you

I just run the ps_select.m line by line in one patch. I noticed that the reason why the coh_thresh are always 1.000 in the result is that the value of "ok_ix" is empty, which means all the "percent_rand" are bigger than "max_percent_rand".  Is this the case you just said?

there was no error in the coregistration step, but I acctually I did not use the parameters for xband. I will check on that. 

my test site is a volcano. the coherence are good in fact, and the interferograms I got looks good too. every step was ended normally until this step. 

I will think your advice over. they are very valuable. Thank you very much!

cheers

Yu

[陈宇]

Hi David,

I would like to ask a quetion about ps_select.m

I use cosmo skeymed data for small baseline. there was 0 PS selected in whole image when i run stamps(3,3). the messages are below. I tried to raise the density_rand to 5, 10, and 20. but same problem happened. 

Have you had a problem like this?

GETPARM: slc_osf=1 

GETPARM: clap_alpha=1 

GETPARM: clap_beta=0.3 

GETPARM: clap_win=32 

GETPARM: select_method='DENSITY'

GETPARM: density_rand=2 

GETPARM: gamma_stdev_reject=0 

GETPARM: small_baseline_flag='y'

GETPARM: drop_ifg_index= 

PS_SELECT: Initial gamma threshold: 1.000 at D_A=0.02 to 1.000 at D_A=0.60

PS_SELECT: 0 PS selected initially

PS_SELECT: Reestimation gamma threshold: 1.000 at D_A=0.02 to 1.000 at D_A=0.60

PS_SELECT: 0 ps selected after re-estimation of coherence

PS_SELECT: Finished

I run the ps_select.m line by line in one patch. I noticed that the reason why the coh_thresh are always 1.000 in the result is that the value of "ok_ix" is empty, which means all the "percent_rand" are bigger than "max_percent_rand".  one thing not normal is that the "percent_rand" values are too big like hundreds , thousands, which make it impossible to get through this no matter what "max_percent_rand" value we set. 

do you know what is the reason for this kind of problem? 

Thank you very much

all the best

Yu CHEN