Difference between vertical and LOS displacement

[ctheodor]

Thanks a lot Dr Braun

[ctheodor]

@johngan May I ask how you created the interferograms’ stack?

[johngan]

Hi,

For stacking you need to do the following:

• Collect a time series SLC SENTINEL-1 images
• Perform InSAR analysis for each image pair
• Terrain correct each pair
• Create stack (Radar->co-registration->stack tools->create stack)

[zhuhaxixiong]

hello Johngan, I have finished all the steps in PS procedure,and get the PS displacement in stamps_visualizer ,the result shows like this:

what i doubt is the direction of the distance in the picture,it is a LOS distance or a vertical distance,if it is LOS distance,how can i convet it to a vertical distance.
all what i want to do is because i have get the LEVELLING data of my area ,so i want to compare the PS result to the levlling result

[zhuhaxixiong]

hi,FeiLiu, i also want to compare my ps result to levelling data,but dont know how to convert it to vertical displacement?
can you help me

[ABraun]

SNAP cannot do that, but it has been discussed several times in this forum:

Phase to Displacement Units?

It’s a change of vector basis from LOS-vectors (+the orthogonal 3rd basis vector) to a new 3D vector basis (easting. northing. up). The formulas get quite involved, see for example: https://www.researchgate.net/profile/Xiaoli_Ding2/publication/225604929_Inferring_three-dimensional_surface_displacement_field_by_combining_SAR_interferometric_phase_and_amplitude_information_of_ascending_and_descending_orbits/links/00b4952428c1a31364000000.pdf

Difference between vertical and LOS displacement

Strictly speaking, to get the optimum results in intereforometry, the satellite orbits should be the same. The limitation of this is that only one surface displacement vector can be resolved. So, many studies carried out using both ascending and descending orbits to isolate vertical from horizontal motion. have a look on these articles. You can collect a few images derived by both ascending and descending orbits and do the interferometric processing and see what you get. Your graph looks…

Difference between vertical and LOS displacement

This article is pertinent to the discussion at hand:

[muhammadasif1]

Mr. ABraun how can i change unit to mm. As you discussed above, kindly write from initial till end that how can i open a band math (unw_Phasewavelength in mm) / (-4PI* cos(red(incident_angle))) i have mentioned the band math but here i am not able to do any thinng.

[ABraun]

Its well described in this topic: Subsidence map in 3d view

You don’t need to change che unit, for example, instead of 3.1 [cm] you simply write 31 [mm]

[seismo]

Dear all,

How may I export ascii file including lat lon east north and up from unwrapped interfrogram in SNAP ?
Anybody has any idea?

Thanks is advance.

[pulido]

Hi, Mengdahl, do you can please say me what is the incidence angle over of the elipsoide?

[seismo]

How may I export ascii file including lat lon east north and up from unwrapped interfrogram in SNAP ?

Dear Andreas,

Just a question on the LOS export.
How may I export ascii file including lat lon east north and up from unwrapped interfrogram in SNAP(after importing unwrapped interfrogram from snaphu) ? I couldn’t find this subject in the forum and in the S1 manual.

Thank you.

[ABraun]

as far as I know, SNAP doesn’t support ASCII export, but you can use gdal, for example:

https://www.gdal.org/gdal_translate.html

But ASCII files can only contain one raster at a time, so you will have to repeat it for any information you need. Make sure you check lat/lon files and elevation in the interferogram step.

The geometric/dem bands might be lost after unwrapping but as it is the same geometry, you can use the rasters fom the inteferogram product:

Navigate to your directory:

gdal_translate -of GTiff .\elevation.img elevation_out.asc

You find similar answers here: https://gis.stackexchange.com/questions/59323/convert-geotiff-to-simple-xyz-elevation-file

You can also do this in QGIS, for example.

[seismo]

Thank you for your time and reply.

Is there any plugin in the SNAP to convert LOS displacement to three components (NS,EW,UP/DOWN)?

[ABraun]

I don’t think so.

[seismo]

Thank you!

Cheers

[mengdahl]

We could add it in the future from ascending/descending analysis.

[Duoc]

Dear @johngan,
The your results in LOS geometry is nice, I am new in PSInSAR technique.
Can you share for me and formun the proscessing that you run subsidence for the area of Ho Chi Minh in Viet Nam.
It is necessaryfor me and my thesis.

Thank you so much.

[ABraun]

please have a look here: About the STaMPS category

[Duoc]

Thank you @ABraun
I try do this tutorial but I have problem with Step 2 (like figure).
Do you have idea to reslove this problem?

Thank you in advance.

[ABraun]

I don’t know, sorry