Improved Ice Velocity Measurements with Sentinel-1 TOPS Interferometry

Jonas Kvist Andersen, A. Kusk, John Peter Merryman Boncori, Anne Munck Solgaard, C. S. Hvidberg, Aslak Grinsted

Publikation: KonferencebidragAbstract ved konferencepeer review

Abstrakt

The Copernicus Sentinel-1 Synthetic Aperture Radar (SAR) system, featuring a 6-day repeat pass period and the Interferometric Wide Swath (IW) acquisition mode, is currently the most commonly applied system for acquiring ice sheet and outlet glacier motion measurements. Such measurements are routinely generated using offset tracking techniques. These methods have the advantage of being applicable even on fast-flowing outlet glaciers, although in the ice-sheet interior significant temporal averaging is required to reduce the measurement errors and observe the underlying ice velocities. Furthermore, the achievable spatial resolution is, at best, several hundred meters. Conversely, differential SAR interferometry (DInSAR) generally achieves high accuracy and high spatial resolution (on the order of tens of meters), while not being applicable on very fast-flowing outlet glaciers. An obvious synergy thus lies in applying both offset tracking and interferometric techniques to the Sentinel-1 data archive, yielding velocity measurements of high accuracy and resolution in the interior parts of the Greenland ice sheet as well as an extensive coverage of outlet glaciers provided by offset tracking. While such a combination of SAR techniques has been exploited in the generation of Greenland/Antarctic ice velocity maps [1,2], Sentinel-1 interferometry is not currently applied for the generation of such products. This is mainly due to a feature of Sentinel-1’s main acquisition mode, namely Terrain Observation by Progressive Scans (TOPS), in which the azimuth antenna steering introduces a coupling between interferometric phase and azimuth registration [3]. This in turn complicates interferometric processing and requires a highly accurate azimuth coregistration procedure. To this end, Extended Spectral Diversity has been successfully utilized in scenes that are nearly stationary [4], however this is not straightforward for ice sheets, which are non-stationary. If not accounted for, the azimuth motion component of the ice sheet will cause interferometric phase gradients across each burst, resulting in phase discontinuities at burst boundaries. We present a Sentinel-1 interferometric processing chain, which reduces the azimuth coupling to the line-of-sight phase signal through a spatially adaptive coregistration refinement incorporating azimuth velocity measurements [5]. The latter are based on available multi-year ice velocity mosaics, optionally supplemented by Burst-Overlap Multi-Aperture Interferometry [5,6]. The DInSAR processing chain is demonstrated for a large drainage basin in Northeast Greenland, which includes the Northeast Greenland Ice Stream (NEGIS), and integrated with state-of-the-art offset tracking measurements. In the ice sheet interior the combined DInSAR and offset tracking ice velocity product provides a spatial resolution of 50 m x 50 m and 1-sigma accuracies of 0.18 m/y and 0.44 m/y in the x and y components respectively, compared to EastGRIP GPS measurements. References [1] I. Joughin, Ice-sheet velocity mapping: A combined interferometric and speckle-tracking approach, Annals of Glaciology 34 (2002) [2] J. Mouginot, E. Rignot, B. Scheuchl, and R. Millan, Comprehensive annual ice sheet velocity mapping using Landsat-8, Sentinel-1, and RADARSAT-2 data, Remote Sensing 9 (2017) [3] N. Yague-Martinez, P. Prats-Iraola, F. Rodriguez, R. Brcic, R. Shau, D. Geudtner, M. Eineder, and R. Bamler, Interferometric Processing of Sentinel-1 TOPS Data, IEEE Transactions on Geoscience and Remote Sensing 54 (2016) [4] R. Scheiber, M. Jager, P. Prats-Iraola, F. De Zan, and D. Geudtner, Speckle tracking and interferometric processing of TerraSAR-X TOPS data for mapping nonstationary scenarios, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 8 (2014) [5] Andersen, J. K., Kusk, A., Merryman Boncori, J. P., Hvidberg, C. S., Grinsted, A., Improved Ice Velocity Measure-ments with Sentinel-1 TOPS Interferometry, Remote Sensing 12(12), (2020) [6] Kusk, A., Andersen, J. K., Merryman Boncori, J. P., Burst Overlap Coregistration for Sentinel-1 TOPS DInSAR IceVelocity Measurements, in press, IEEE Geoscience and Remote Sensing Letters, (2021)
OriginalsprogEngelsk
StatusUdgivet - 2021

Programområde

  • Programområde 5: Natur og klima

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