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.
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:
Read
Apply Orbit
Calibration
TOPSAR-Deburst
SAR Simulatin
GCP-Selection
SARSim
Write
or
Read
Apply Orbit
Calibration
TOPSAR-Deburst
Range Doppler Terrain Correction
Write
I got the same Exception error : org.esa.snap.core.gpf.graph.GraphException
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?
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)?
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.