Improved DInSAR time series using high-resolution optical DEMs

Differential interferometric synthetic aperture radar (DInSAR) can measure surface deformation at the centimeter level and, as a result, has been used to investigate a wide variety of natural hazards since the 1990s. In general, short spatial and temporal baselines are selected to reduce decorrelation and the effect of incorrect removal of the topographic component in differential interferograms. The nearly global coverage of the Shuttle Radar Topography Mission (SRTM) digital elevation models (DEMs) significantly simplified and improved the modelling and removal of topography for differential interferometric applications. However, while SRTM DEMs are freely available at 30 m resolution world-wide and 10 m resolution in the US, they do not cover the Arctic and Antarctic, and DEMs can be produced today at much finer resolutions, with varying availability and cost. The TanDEM-X mission has produced a worldwide DEM at 12 m, although it is not generally free of cost. Light Detection and Ranging (LiDAR) DEMs can provide better than 1m resolution but are expensive to produce over limited extents. Finally, DEMs from optical data are produced from Digital Globe satellite images over larger regions at resolutions of less than 1 m, subject to various restrictions. DEM resolution is one of only a few defining parameters that directly affects the coherence quality of a DInSAR image. Higher resolutions can improve the recovery of the differential phase by reducing the geometric decorrelation, such that the number of recovered pixels significantly increases with higher resolutions, particularly in steep topography. In this work we quantify that improvement for varying slopes, land use types and resolutions, from 1 to 30 m, and investigate its effect on DInSAR results for a variety of environmental processes and regions.