Coherence workflow

Available with Image Analyst license.

Single look complex (SLC) synthetic aperture radar (SAR) image pairs must be processed before coherence can be generated. Coherence measures the phase similarity between two acquisitions, which provides insight into surface stability and change. The coherence workflow requires that the reference and secondary SLCs are aligned to a common geometry before the coherence can be computed. Orthorectifying the SAR dataset allows for mapping and analysis.

Coherence for Sentinel-1

The Synthetic Aperture Radar toolset contains tools you can use to generate coherence rasters from Sentinel-1 SLC pairs.

Step	Tool	Description
1	Download Orbit File	Downloads the updated orbit files for Sentinel-1 synthetic aperture radar (SAR) data.
2	Apply Orbit Correction	Updates the orbital information in the Sentinel-1 synthetic aperture radar (SAR) data using a more accurate orbit state vector (OSV) file.
3	Apply Coregistration	Resamples the secondary single look complex (SLC) data to the reference SLC grid using a digital elevation model (DEM) and orbit state vector metadata.
4	Compute Coherence	Computes the similarity between the reference and secondary input complex radar data.
5	Deburst	Merges the multiple bursts from the input Sentinel-1 Single Look Complex (SLC) synthetic aperture radar (SAR) data and outputs a single, seamless subswath raster. This step is only needed for IW and EW modes that are acquired using the Terrain Observation by Progressive Scan (TOPS) imaging technique.
6	Apply Geometric Terrain Correction	Orthorectifies the input synthetic aperture radar (SAR) data using a range-Doppler backgeocoding algorithm.

Processing considerations

Supported S1 SLC modes are Interferometric Wide Swath (IW), Extra Wide Swath (EW), and Stripmap (SM). The Deburst tool is only needed for IW and EW modes that are acquired using the Terrain Observation by Progressive Scan (TOPS) imaging technique. For S1 SLC Stripmap (SM), omit the Deburst tool from the workflow.

When you download and apply the orbit files, consider the type of orbit state vectors (OSVs) you'll use. The following types of OSVs are available for the Sentinel-1 product:

• Predicted—Provided with the Sentinel-1 Level 1 ground range detected (GRD) and SLC auxiliary products.
• Restituted—Available through the European Space Agency (ESA) within three hours of image acquisition.
• Precise—Available through ESA within three weeks of image acquisition.

It is recommended that you update the OSVs to restituted or precise once they are available.

Coherence for other sensors

The Synthetic Aperture Radar toolset contains tools you can use to generate coherence rasters from Capella SICD, ICEYE SICD, RADARSAT-2 SLC, or RADARSAT Constellation Mission (RCM) SLC.

Step	Tool	Description
1	Apply Coregistration	Resamples the secondary single look complex (SLC) data to the reference SLC grid using a digital elevation model (DEM) and orbit state vector metadata.
2	Compute Coherence	Computes the similarity between the reference and secondary input complex radar data.
3	Apply Geometric Terrain Correction	Orthorectifies the input synthetic aperture radar (SAR) data using a range-Doppler backgeocoding algorithm.