A Deformation Compensated Offset Tracking for the High-Velocity Glaciers at Greenland Ice Sheet

Offset tracking (OT) is a primary method for monitoring glacier motion in high-velocity regions, where displacement is typically estimated by template matching in the frequency domain. However, this method relies on the rigid-body shift assumption of the image template and neglects internal deformation within the template, which may reduce coherence and introduce errors in displacement estimation. Here, we propose a deformation compensation method to eliminate the effects of internal deformation within the template. First, a preset deformation field is formed based on a long-term average flow velocity field and the SAR observation geometry. Then the pre-event image is shifted pixel-wise according to the preset deformation field to establish a simulated post-event image. Afterwards, the residual deformation is obtained by performing the OT method between the simulated post-event image and the real post-event image. The final deformation field is the sum of the preset deformation field and the residual. We selected four glaciers in Greenland and applied the proposed method to Sentinel-1 SAR images. The obtained velocity fields were compared with published velocity products and those derived from the traditional OT method. In the top 10% high-velocity regions, compared with the traditional OT method, the proposed method achieves average improvements of 103.84% in spatial coverage and 1.96 in signal-to-noise ratio (SNR); compared with the published velocity products, the spatial coverage improvement averages 92.44%. The results demonstrate that the proposed deformation compensated OT method effectively reduces monitoring failures in high-velocity glacier regions and significantly improves the coverage of velocity fields, especially in high-velocity areas. This research can be further applied to both polar and alpine regions for glacier dynamic studies.