Using repeat pass, overlapping images, this processing block calculates cumulative ground displacement as well as deformation velocity.
The CATALYST Ground Displacement processing block makes use of repeat pass Sentinel-1 SLC images to calculate cumulative displacement using sequential InSAR processing techniques (A-B, B-C, C-D, etc) based on the number of images requested.
Output products generated include cumulative displacement and velocity measurements (relative to first image in the stack). A quality measure is also generated (average coherence) as well as reference backscatter image. All results are orthorectified, and measured in relative units, in the line of sight of the sensor).
This block can be used with the following workflow:
- Sentinel-1 L1 SLC (SAFE) -> Ground Displacement
For running this workflow, the image IDs of matching Sentinel-1 InSAR image pairs need to be specified in the data block (see below) and the AOI needs to be defined as a JSON in the processing block.
Catalyst recommends choosing an arid, or semi-arid area for this type of processing. It is important to perform a data search prior to execution, and carefully selecting images that overlap the chosen location(s).
Processing will be completed on individual pairs of overlapping images. Users can combine S1A and S1B (where available), however the requested AOI should be inside the overlap area. If the AOI overlaps along track, two separate sets of products will be generated for each set of InSAR pairs.
How to identify InSAR pairs using the preferred search tool (such as Scihub):
- Draw AOI
- Select “Sentinel-1” as the mission, and “SLC” as the product type.
- To narrow the search, choose the preferred look direction (Ascending or Descending), and explore the image that best fits the AOI.
- Using the “relative orbit” number (found under Product), refine your search further with dates of interest and your AOI.
- Record the Scene IDs to be used in the processing block.
Input Parameter Description
- Sentinel-1 Scene IDs (ascii string)
- Area of interest (geojson)
- Processing mode
- https://geojson.io/ or other similar OGC compliant GeoJSON AOI generators can be used for the GeoJSON
Output Parameter Description
Using the AOI properties, the clipped results will be generated in GeoTIFF format (output) with a raster channel representing each pair.
- Cumulative displacement: 32R, Unit - millimeters
Velocity: 32R, Unit - millimeters per year
Coherence: 32R, Unit - range from 0 (low coherence) to 1 (high coherence)
The minimum number of pixels in either direction must be at least 2000.
Acceptable example: 2000 pixels x 2000 lines (SLC Sentinel-1 images) = ~7 km x 27 km
Unacceptable example:1500 pixels x 2000 lines (SLC Sentinel-1 images) = ~5.5 km x 27 km
A minimum of 2 images must be used, and the total price will be calculated as follows:
“"n"” images in stack * km2 * credits per km2
1 time slice: 2 images * 200 km2 * 5 = 2* 200 * 5 = 2000 credits (20 Euros)
10 time slices: 11 images * 200 km2 * 5 = 11 * 200 * 5 = 11,000 credits (110 Euros)
The number of displacement measurements (time slices) will always be equal to “"n"” images -1
See applications of ground deformation maps on the partner website.
Block Access & Demo
To access the block and get a personal demo, please contact [email protected].