Abstract ID: 28.7417 | Accepted as Poster | Poster | 2025-02-28 12:45 - 14:15 | Ágnes‐Heller‐Haus/Small Lecture Room

Satellite stereo photogrammetry is commonly used for quantifying glacier elevation changes and computing geodetic glacier mass balances, particularly at regional to global scales. Several satellite sensors enable stereo or tri-stereo imaging for DEM generation, including the Terra ASTER, SPOT 5 HRS, SPOT 6-7 NAOMI, Pléiades HiRI, and Pléiades Neo Imager. Each has advantages and limitations in terms of spatial resolution, temporal coverage, and data availability. Since 2000, ASTER has provided a 20-year global stereo archive. However, the coarse DEM resolution of ~30 m is not optimal for capturing changes in small alpine glaciers. SPOT 6-7 and Pléiades offer finer resolutions (1.5 m–0.3 m), but their usage is limited by shorter time series, higher costs, and limited stereo archives. The Pléiades Glacier Observatory provides publicly accessible 2 m DEMs for 140 glacierized areas with ~5-year revisit intervals, but its time series starts only in 2016.
This study aims to assess the capabilities and challenges of the SPOT 5 HRS archive for glacier elevation changes in the Alps. Operating from 2002 to 2015, SPOT 5 HRS offers global coverage with a resolution about 4.5 times finer than ASTER and a swath width of 120 km, enabling ~10 m resolution DEMs. Since 2021, CNES has made SPOT 5 imagery freely available through the SPOT World Heritage program. Although SPOT 5’s temporal coverage complements newer commercial stereo satellites and provides high-resolution elevation changes for the early 21st century, it remains underutilized for glaciological analysis. Challenges include its 8-bit radiometric resolution, the lack of Rational Polynomial Coefficients (RPC) camera models, which must be computed from the exact camera models, and rectangular pixels caused by the 10 m image resolution at nadir with 5 m along-track oversampling.
We analyzed the spatial and temporal coverage of the SPOT 5 HRS archive for Alpine glaciers, focusing on the availability of stereo pairs and seasonal acquisition patterns. Case studies on the Aletsch and Belvedere Glaciers benchmark SPOT 5 stereo reconstruction and DEM accuracy against ASTER. Glacier elevation changes over multiple decades are estimated using SPOT 5, SPOT 6-7, and Pléiades datasets and validated against ASTER-derived estimates.
Despite SPOT 5’s challenges, the archive offers a valuable resource for the glaciological community, as it fills a critical gap for long-term analyses of glacier elevation changes.