SNAP processing SAR images for denoising

This post is about workflow of SAR data process in SNAP before denoising.

SNAP

Processing of SAR data

1. Load SAR data in SNAP

2. Apply orbit file: Radar -> Apply Orbit Files

   This step makes no impact to origin SAR files, but modify the metadata.xml file.

3. Calibrate: Radar -> Radiometric -> Calibrate

   In Tab2 change saving output to ‘Save as complex output’ instead of ‘output sigma0 band’
   

4. Deburst: Radar -> Sentinel-1 TOPS -> S-1 TOPS Deburst

5. Generate C2 Metrix: Radar -> Polarimetric -> Polarimetric Matrix Generation

   In tab2 choose C2 metrix, and this step should be done after deburst.
   

6. Multilooking: Radar -> Multilooking

7. Terrain Correction: Radar -> Geometric -> Terrain Correction -> Range-Doppler Terrain Correction

   Make sure to deselect option ‘Mask out areas without elevation’ when dealing with ocean area.

8. Write

Process with SNAP gpt tool

1. Config environmet variable in system PATH

2. Type command gpt Apply-Orbit-File -h in cmd

3. Type command C:\Users\mengy>gpt Apply-Orbit-File -Ssource="D:\DATA\Sentinel\Xuzhou\Unzip\S1A_IW_SLC__1SDV_20160805T101148_20160805T101215_012464_01379E_AF42\S1A_IW_SLC__1SDV_20160805T101148_20160805T101215_012464_01379E_AF42.SAFE" -t "C:\Users\mengy\Documents\DATA\Sentinel\test\S1A_IW_SLC__1SDV_20160805T101148_20160805T101215_012464_01379E_AF42_orb_test.dim" in cmd

Process with SNAP gpt graph tool

1. Read -> $input1

2. write -> output
   C:\Users\mengy\Documents\DATA\Sentinel\test\S1A_IW_SLC__1SDV_20160805T101148_20160805T101215_012464_01379E_AF42_Orb_Cal_Deb_mrg_ML_TC.tif

Process with QGIS

1. Clip output file S1_xuzhou_20160805.tif with xuzhou_centre.shp

   target CRS: EPSG:4326 - WGS 84
   assign a specified nodata value to output band to 0.00 (otherwise output a rectangle)

2. Export output to computer disk

   save as S1_xuzhou_20160805_clip.tif