Geology & Environmental Science Colloquium: Dr. Shashank Bhushan | University of Maryland Earth System Science Interdisciplinary Center and NASA Goddard Space Flight Center's Biospheric Sciences Laboratory

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Decimeter-accuracy Surface Topography from Commercial Satellite Stereo Imagery: Method Advancements and Earth Science Applications

Presented by Dr. Shashank Bhushan | Assistant Research Scientist at the University of Maryland Earth System Science Interdisciplinary Center and NASA Goddard Space Flight Center's Biospheric Sciences Laboratory

Talk Abstract:

Very high-resolution (VHR) satellite topography derived from commercial electro-optical line-scan imagery enables detection of subtle Earth surface changes at high spatio-temporal resolution. In this talk, I discuss the development of satellite photogrammetry workflows to measure seasonal glacier dynamics in Nepal Himalaya and volcanic flows in Mauna Loa, Hawaii, demonstrating both the scientific promise and practical limitations of current methods. I show how unmodeled satellite attitude variations (jitter) introduce systematic small-scale elevation artifacts (>50 cm) that preclude small-magnitude topographic change detection, and present new correction algorithms that resolve these errors. The workflow utilizes automatic ground control from globally available reference elevation measurements derived from sparse profiling lidar (NASA's ICESat-2) and/or low-resolution radar-derived Digital Elevation Model composites (Copernicus GLO-30) to iteratively refine sensor model pose during line-scan image collection. The DEMs obtained from updated sensor models achieve decimeter elevation accuracy (<15 cm) over low-relief sites, with considerable vertical accuracy improvements also observed over high-relief sites. In essence, this workflow combines the large-area, high-resolution mapping capabilities of satellite photogrammetry (2 m) with globally available low-resolution but high vertical accuracy ground control. Together, these advances will enable new studies of glacier mass balance, vegetation structure, shallow water bathymetry, and other geomorphic processes at unprecedented precision.

Biography:

Dr. Shashank Bhushan is an Assistant Research Scientist at the University of Maryland Earth System Science Interdisciplinary Center and NASA Goddard Space Flight Center's Biospheric Sciences Laboratory. His research centers on satellite photogrammetry and lidar algorithm development, multi-modal data harmonization, and geolocation correction—techniques he uses to observe glacier mass balance and dynamics, vegetation structure, and shallow water bathymetry from space.

Shashank's journey in remote sensing began with mountain glaciology research during his undergraduate studies. In graduate school, he developed photogrammetry workflows to derive accurate geodetic products from commercial satellite imagery (Planet Labs, Vantor) and leveraged these observations to understand surface and climatic processes controlling debris-covered glacier mass balance in High-Mountain Asia. At NASA Goddard, his work contributes to NASA's Cryospheric Sciences and Biospheric Sciences programs, the Decadal Survey Incubation Surface Topography and Vegetation targeted observable, the Harmonized Landsat Sentinel-2 Project, and the Sustainable Land Imaging Commercialization project.