Bug: TC and TF do not work in Graph Builder with external DEM (beta 08)

Microwave Toolbox Problem Reports
1

I am able to use both terrain flattening and terrain correction by calling these operators from the menu system, however I am unable to get them to operate in graph builder mode.

I am using a custom DEM (as I am at a high latitude not covered by SRTM). When I chose the built in DEMs that cover this region, the operation works fine.

But, if using my custom DEM (that works fine outside of graph mode), I get the notice org.esa.snap.core.gpf.graph.GraphException and I am unable to run the operation.

I have tried this in both Mac and Windows using SNAP beta 2.0 08.

2

apologies if this should have been posted elsewhere.

I’ll also report that the graph works fine running via gpt in the command line.

3

I also got this exception when tyring to run SAR Simulation Terrain Correction using our own DEM from the menu.

However Range Doppler Terrain Correction runs just fine as a wizard from the menu using our own external DEM. I got a raster what is orthocorrected and resampled to 15 m and has UTM as a reference system. (Besides it creates an output which is shifted by 1-3 pixels compared to optical satellite imagery like SPOT (10m) or pansharpened Landsat 8 (15 m). The optical images are in the same spatial reference system (UTM) and very well registrated intrinsically. I added the geoid undulation to the DEM in order to get Elliposidal Height instead of Elevation. The shift is still present.)

If I try to construct a Graph as follows:

  1. Read
  2. Apply Orbit
  3. Calibration
  4. TOPSAR-Deburst
  5. SAR Simulatin
  6. GCP-Selection
  7. SARSim
  8. Write

or

  1. Read
  2. Apply Orbit
  3. Calibration
  4. TOPSAR-Deburst
  5. Range Doppler Terrain Correction
  6. Write

I got the same Exception error : org.esa.snap.core.gpf.graph.GraphException

I use SNAP 2.0-beta-08 on Windows 7.

4

Hello. I’ve got the same error :org.esa.snap.core.gpf.graph.GraphException when I try to use the Range Doppler Terrain Correction on a graph (no problem when I do it from the menu system). I use a custom DEM and I use SNAP beta2.0.08 on Ubuntu 14.0.LTS.
Did you find the solution?

5

Is there a reason why you apparently use SLC-products even though you don’t appear to use the phase for anything (phase is unusable after Terrain Correction)?

7

Nope, I was going to try on Debian but after your post I suppose it doesnt matter…
Have you got any shift on the orthocorrected image?

8

Basically we plan to orthocorrect Polarimetric descriptors which is derived from SLC-product using other software like Polsarpro. I just regard as easier and quicker to calibrate SLC to get a dataset for testing that can be orthocorrected.

9

Hello,

I get the same error when using custom DEM with Terrain.Correction tool. Graph builder says ‘org.esa.snap.core.gpf.graph.GraphException’.

@forman ?

Kind regards,

Guillaume