Quicklook deformation analysis
We at EarthDaily Analytics (formerly Descartes Labs) have built a number of tools over the last few years to work with Sentinel-1 data quickly and efficiently. The "Quicklook analysis" tool in "Iris" can be used to quickly generate InSAR time-series over small AOIs interest. The quicklook analysis is very useful in understanding the spatial distribution of reliable scatterers over an AOI and also helps identify key deforming features quickly, when possible. Our quicklook analysis, builds on our Global InSAR layer which includes all interferograms with a temporal baseline less than 24 days.
Launching a quicklook analysis¤
Here, we select an AOI over Wink, TX and a time period of interest (1 year) along with some processing parameters like output posting and a couple of thresholds for analysis. When we hit the "Submit" button, this launches a processing job within the "Compute" service on our platform which the user can continue tracking. This "Compute" job pulls data from our platform, processes it according to the selected parameters and writes results back to our "Storage" service as a parquet file. The exact processing time for each analysis depends on the requested output posting, size of the AOI, the number of epochs in the selected time span and density of reliable scatterers in the AOI. Once you submit a job - go grab a coffee or continue working through your AOIs / visualize results of other analyses. Typically, the job like the one in the video above takes 15-20 minutes. If we were to choose an output posting of 40m for this example, it would be done in less than 5 minutes.
Visualizing the results¤
The results of our analysis will be available along with other "Quicklook" analyses as shown in the video above. The user is able to interactively load the results and visualize / analyze them. The results in the form of a parquet file can also be downloaded from our "Storage" service and visualized directly in QGIS with appropriate time series viewer plugins.
Quicklook vs GDS analysis¤
We note that the "Quicklook" processing pipeline is different from our more rigorous full resolution "GDS" pipeline that generates uncertainty estimates as well, even though they share a lot of common modules including the unwrappers. The main differences are summarized in the table below:
| Feature | Quicklook | GDS |
|---|---|---|
| Inputs | Multilooked interferograms with Btemp \< 25 days | Geocoded SLCs |
| Time series inversion | Daisy chain | Phase linking using the correlation matrix |
| Uncertainty estimates | No | Yes |
| Pixel selection criterion | Temporal coherence | Temporal coherence and uncertainty estimates |
| Pixel relocation | No | Yes. Can visualize original raster grid or relocated points |
| Sensitivity | Suitable for large signals or rates > 1 cm/yr over coherent areas | Rigorous analysis on par with state-of-the-art techniques |
The "Quicklook" results should be treated as preliminary results that can assist in evaluating AOIs and are not to be considered on par in terms of quality with the results from the more rigorous full resolution processing pipeline that starts with geocoded SLCs.
Gallery of Quicklook results¤
Click on the link above to access the quicklook gallery. This collection of results is by no means complete, i.e. it only represents a fraction of number of the analyses we have performed for testing, but hopefully is sufficient to demonstrate that we are able to reliably identify and highlight known deformation signals in a few minutes using our "Quicklook" system.