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

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.