A GIS Method of Calculating Snow Depth Using IFSAR Data and Differential Global Position System

Recent advances in remote sensing platforms, Differential Global Positioning Systems (DGPS) technology, and Geographic Information Systems (GIS) capabilities has led to multiple ways of creating high resolution Digital Elevation Models (DEM). In April 2005 near Barrow, Alaska, a DGPS survey was conducted along a snowdrift formed by a 2.2 km long snow fence. A snow machine was used to pull a sledge equipped with the DGPS, recording geographic location and elevation every 5 seconds. Surveys were conducted along five transects parallel to the snow fence; two along the upwind (eastern) side of the fence and three along the deeper downwind (western) drift. The path of the snow machine was along the drift crest, slope and edge. In addition to the DGPS survey of the snowdrift, Interferometric Synthetic Aperture Radar (IFSAR) data collected in July 2002 by InterMapr was used as a DEM of the ground surface. Within the GIS software package, the DGPS survey points were interpolated using a triangulated irregular network. This surface was rasterized to 5 m2 cells to match the IFSAR DEM. Using a raster calculator, the ground surface DEM was subtracted from the snowdrift DEM to yield a DEM of snow depth. Integrated over the length and width of the affected area, the drift covers an area of 186,900 m2 and contains a volume of 415,858 m3. The mean snow depth is 2.23 m as compared to 0.4 m at a control site located in a nearby region of the tundra unaffected by the snow fence. Empirical measurements were collected with a calibrated metal snow depth probe along transects perpendicular to the snow fence, and were used for an accuracy assessment. The results show agreement to about +/-20 cm. Some Arctic villages rely on snowdrifts as a source of drinking water. Using these techniques, the snow water equivalent can be calculated given a know snow density to estimate fresh water availability.