Sentinel-1 Analysis Ready Data - A Convenient and Easy to Use System Producing Common-coordinate Timeseries

We have developed and make available a set of Sentienl-1 processing code and algorithms for routine generation of InSAR timeseries that are in analysis-ready (ARD) form: products in common coordinates rather than radar range-Doppler reference, with all phase compensation terms from variable viewing geometry and topography applied. Since the data are in ARD formats, end users require little to no radar processing expertise to be able to productively and easily incorporate InSAR analysis into their applications and research.

We use Sentinel-1 TOPS data to provide worldwide coverage and much temporal availability. Adapting it for other sensors requires the addition of the SAR focusing code capable of supporting other sensors. Since Sentinel-1 provides such a comprehensive set of data at no cost to users, we have limited our implementation to that source for now.

Our approach is a backprojection algorithm to focus TOPS mode wide swath acquisitions directly to locations specified by a digital elevation model. The code defaults to use the Copernicus DEM for registering all products, but another DEM may be provided as needed. The single look complex images are automatically compensated for all propagation phases, including elevation, so that they align exactly and interferograms can be formed by simple cross multiplication. After phase unwrapping using the Snaphu algorithm, we select 100's to 1000's of reference pixels per scene to minimize atmospheric influence on the final timeseries, and we further reduce the tropospheric phases by regression against elevation. The final step is applying the SBAS algorithm to generate timeseries.

We find the package easy to use and reasonably fast compared to other approaches. Because we use the backprojection algorithm rather than range-Doppler, it is not necessary to oversample the azimuth phase history and its consequent precision alignment needs. If systems contain GPU elements, these are used for faster computations. The combination of a simple interface plus data products in friendly coordinates are a good demonstration of the possibilities of designing in analysis-ready capabilities in a radar processing system. We hope to get significant feedback and improvements from the wider community that can help improve our ability to provide useful observations for many applications.