DEM generation of Sentinel-1 Data is showing negative elevation

DEM generation of Sentinel-1 Data is showing negative elevation
I generated interferogram in SNAP Software and did phase unwrapping in SNAPHU but the result is showing negative elevation.
DATA Details:Sentinel-1 IW SLC products over the 2014 eruption of the Fogo volcano in Cape Verde.
SENTINEL-1
Data 1 Data 2
Acquisition mode IW IW
Antenna pointing Right Right
Incidence near 99,999 99,999
Incidence far 99,999 99,999
Range spacing 2.33 2.33
Azimuth spacing 13.997 13.997
Product Time 28-NOV-2014 14:05:34.340674 28-NOV-2014 14:35:25.183413

Radar Frequency 5,405 MHz 9,650 MHz
Pass Ascending Ascending


Can you please list the steps you undertook to get this?

What SAR measures is the relative difference between two images, hence, you get relative heights.
To get absolute heights, you need to identify a location on your map with known elevation

Step 1. Opening a Pair of SLC Products ………………………
Step 2. S-1 TOPS Coregistration …………………………….
Step 3. Interferrogram Generation ………………………
Step 4. S-1 TOPS Deburst ……………………………………
Step 5. Topographic Phase Removal …………………
Step 6. Goldstein Phase Filtering ……………………
Step 7. Phase Unwrapping …………………….
1. SNAPHU Export …………………
2. SNAPHU Import …………………
Step 8. Phase to Elevation ……………………………

Topographic phase removal doesn’t make much sense to me here because this is what you try to measure. I personally would skip it.

@johngan That is true for the ‘Phase to height’ operator, but ‘Phase to elevation’ is doing this somehow.

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can you explain in detail on how to convert the relative height to absolute height ? or is there any tutorial or document to help in converting from relative to absolute height ? :slight_smile:

Hi,

In SNAP you can do, phase to elevation to get absolute heights
I do not know if that’s what you are looking for

Thank for the reply. :slight_smile: