Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > 2009 Posters
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A New, High-Resolution Digital Elevation Model of West Antarctica Combining MODIS Imagery, ICESat, and Radar Altimetry

Terry M. Haran and Ted A. Scambos

An image enhancement approach is used to develop a new digital elevation map of West Antarctica, combining multiple MODIS images and both radar altimetry and ICESat laser altimetry Digital Elevation Model (DEM) data. The method combines the wide image coverage of MODIS, and its high radiometric sensitivity (which equates to high sunward slope sensitivity), with the high precision and accuracy of ICESat and radar altimetry DEMs.

We calibrate brightness-to-slope relationships ('photofunctions') for a series of MODIS images of the central West Antarctic. Calibration is based on a comparison with a smoothed DEM (smoothing scale, 15km) derived from merging ICESat and radar altimetry data (Bamber, personal communication). Using the photofunctions, we then created, first, a detailed, high-resolution slope map of the ice sheet surface from the image data (regressing slope information from up to 25 images for each 600 by 600 km region), and then integrated this absolute slope map to yield complete DEMs for the region.

A set of cloud-cleared MODIS band 1 data from both the Aqua and Terra platforms acquired during the 2003-2004 austral summer, used in generating the Mosaic of Antarctica, MOA, surface morphology image map, were used for the image enhancement. Past analyses of the slope-brightness relationship for MODIS have shown ice surface slope precisions of ± 0.00015. ICESat spot elevations have nominal precisions of ~5 cm under ideal conditions, although thin-cloud effects and mislocation errors can magnify these. Only cloud-free areas of MODIS scenes that also meet specific slope, grain-size, solar zenith, brightness, latitude, and elevation criteria are used for image enhancement.