InSAR coherence for automated lake ice extent mapping: TanDEM-X bistatic and pursuit monostatic results

Abstract

TanDEM-X bistatic and pursuit monostatic InSAR coherence offer different utility for lake ice extent mapping. Both facilitate ice-water discrimination largely independent of the SAR incidence angle but only pursuit monostatic coherence does so under all wind conditions. Relative to backscatter intensity—the basis for most existing mapping approaches—pursuit monostatic coherence offers enhanced utility. Our automated mapping approach combines basic interferometric processing, ice-water classification using a 0.3 coherence threshold and geospatial analysis to separate lakes from land. The approach is developed and demonstrated using TanDEM-X pursuit monostatic data acquired during freeze-up but should also be of use for the mapping of lake ice breakup. Early in the freeze-up season, the extent of lake ice is underestimated due to the commission of new ice—estimated age ≤ 5 days—in the water class. An evaluation of coherence for sample regions reveals three principal—surface cover and cooperative mode dependent—decorrelation sources: temporal change, additive noise and multiplicative noise. TanDEM-X operated in its pursuit monostatic mode for a limited time in support of scientific studies. The introduction of a system with a fully operational capacity to acquire near-simultaneous InSAR images would benefit operational users concerned with lake ice extent mapping and—we expect—many others that deal with water or other rapidly changing features.