Different result between ascending and descending

[NabilAttar]

Greeting Mr. Yumorishita

I have done to process frame 171A_09587_041313 and 120D_09443_131313 in 105.16/105.36/-5.53/-5.31 geo clip area, but it produces different velocity. In ascending we see that there is an area with up lift and subsidence. But in descending we see there're no area with subsidence, almost all areas experienced uplift. Is my processing wrong? Why does it happen?

Thank you.....

[yumorishita]

Maybe the time period is different?

[NabilAttar]

Maybe the time period is different?

Yes sir, ascending in 2015 - 2023. Descending 2017 - 2023. does it have any effect?

[yumorishita]

I think so. Also, you should check the network and gaps.

[NabilAttar]

I think so. Also, you should check the network and gaps.

in the normal case, should they both have the same velocity? Thank you

[yumorishita]

They are never same because the LOS geometry is different, but they should be similar if there is no horizontal component.

[NabilAttar]

greeting Mr. Yumorishita

this is network between ascending (up) and descending (down). i think that descending is bad because infrenquently IFG, Do you have any suggestions regarding processing results that are not similar? thank you

[yumorishita]

I suggest using the common time period (Aug 2019 - May 2022).

[NabilAttar]

I have tried time period (Aug 2019 - May 2022) in descending. However, there is still only uplift in the surrounding area. Maybe it's already from the IFG data

[NabilAttar]

excuse me sir, sorry for out of topic. I have done ascending and descending processing. but I think the results of descending are quite bad. i have use LiCSBAS_decompose but i think the result of UD is bad caused descending frame. Is it possible to get a UD velocity value just by using ascending? I only need UD and not EW. thank you sir

[ditafaith]

Hi @NabilAttar
If you want to use only 1 orbit, and ensure that horizontal movement very small contribution, then you may extract time series at certain point and divided by cosinus incidence angle. If you want to get an image, may be you can operate gdal_calc for ascending.tiff file.

[NabilAttar]

Hi @NabilAttar If you want to use only 1 orbit, and ensure that horizontal movement very small contribution, then you may extract time series at certain point and divided by cosinus incidence angle. If you want to get an image, may be you can operate gdal_calc for ascending.tiff file.

thank you sir, is gdal_calc same like raster calculator in QGIS? so, formula for get velocity upward/vertical direction tiff is only [velocity LOS.tiff / cos(incidence angle] ?? thank you

[NabilAttar]

Hi @NabilAttar
If you want to use only 1 orbit, and ensure that horizontal movement very small contribution, then you may extract time series at certain point and divided by cosinus incidence angle. If you want to get an image, may be you can operate gdal_calc for ascending.tiff file.

excuse me sir, is my statement correct? Thank you

[yumorishita]

I think your statement is correct.

[NabilAttar]

Thank you sir

[NabilAttar]

greeting Mr. Yumorishita

I want to ask about ascending and descending baselines which I have uploaded. In ascending use dummy unit (look in left side picture), and descending use Bperp unit (baseline perpendicular). why the results are different? in your paper the network result in Bperp unit, what is dummy? thank you

[yumorishita]

If baselines file does not contain the values for all dates, the dummy baseline is used because the correct figure cannot be drawn from the incomplete data. Please check the log in step02 to find what date is lacking in baselines.

LiCSBAS/LiCSBAS_lib/LiCSBAS_io_lib.py

Line 165 in 5db6516

print('ERROR: bperp for {} not found!'.format(imd), file=sys.stderr)

LiCSBAS/bin/LiCSBAS02_ml_prep.py

Line 371 in 5db6516

print(' baselines file found, but not complete. Make dummy', flush=True)

[NabilAttar]

excuse sir, here is "not baseline found" do you have any suggestions? is it a good idea if i delete 20170814 in GEOC and start batch licsbas from step 02? thank you

[NabilAttar]

in metadata network png on GEOC, baseline 20170814 is avaible

[yumorishita]

What is the frame ID?

is it a good idea if i delete 20170814 in GEOC and start batch licsbas from step 02?

Yes, you will get the correct network figure with non-dummy y-axis.

[NabilAttar]

frame ID is 171A_09587_041313

i have tried by deleting 20170814 in GEOC and delete GEOCml1. but another IFG without baseline is found. do you have any suggestions? thank you

[yumorishita]

This is the baseline file used for the network figure:
https://gws-access.jasmin.ac.uk/public/nceo_geohazards/LiCSAR_products/171/171A_09587_041313/metadata/baselines

I found some dates have no data in the 3rd column, e.g.,

20190512 20170802 -65.0 -648
20190512 20170814  -636
20190512 20170826 -52.0 -624

You can manually edit the file and fill the 3rd column, or ask COMET to fix this issue.

[NabilAttar]

how to determine the value of the 3rd column? are there any provisions for fill the 3rd column?

[ditafaith]

how to determine the value of the 3rd column? are there any provisions for fill the 3rd column?

You might try to download the images and check it manually using SNAP software. Also, you can check it through Alaska Satellite Portal. It seems you are working on subsidence in Lampung.

[NabilAttar]

how to determine the value of the 3rd column? are there any provisions for fill the 3rd column?

You might try to download the images and check it manually using SNAP software. Also, you can check it through Alaska Satellite Portal. It seems you are working on subsidence in Lampung.

yes sir, i have research about this area. also i have visited alaska and check baseline manually. I equated it with baseline data from licsar, the perpendicular baseline difference from the missing third column is only about 3 meters. Thank you for the advice