Improved surface and bedrock DEMs have been produced for the Belcher Glacier using data from different sources, including in situ measurements, airborne soundings, and satellite images. Surface elevation is based on 2007 (late summer) SPOT5 HRS images.
Bed elevation values are derived from surface-based ground penetrating radar soundings conducted during the 2007 and 2008 summer field seasons. Airborne radar surveys in 2000 and 2005 by the Scott Polar Research Institute and the Center for Remote Sensing of Ice Sheets, respectively, provide ice thickness data. By subtracting ice thickness from surface elevation using the surface DEM, bedrock elevation values are derived. Additional bedrock elevation data for the seafloor in front of the terminus of Belcher Glacier were obtained from a bathymetric survey in 2006 by workers from Memorial University of Newfoundland and the University of New Brunswick working off the CCGS Amundsen.
A 40-m grid is used as a map base. Bed elevation values were found for each point on the grid by applying a kernel that weighted values of surrounding points by distance. After finding a suitable semivariogram model, statistical interpolation (kriging) was performed to fill in the rest of the grid points to produce the bedrock DEM. As a check, a 1999 Landsat panchromatic image was used to force bedrock elevation to equal surface elevation within the boundaries of rock outcrops and thus ensure that ice thickness is zero throughout.
