Glacier mapping of the Illecillewaet icefield, British Columbia, Canada, using Landsat TM and digital elevation data

Glacier inventory is important to provide estimates of freshwater storage and as an indicator of climate variability. The methodology for glacier inventory in Canada has been based on manual interpretation of aerial photographs. Digital methods using Landsat Thematic Mapper (TM) satellite imagery and terrain models offer improved efficiency and repeatability, while retaining sufficient accuracy and precision. Supervised maximium likelihood classification trials using different input bands were assessed for accuracy of mapping glacier extent and discriminating glacier zones at Illecillewaet Icefield, Glacier National Park, British Columbia. Results were compared with visual image interpretation, with the best results obtained using the combination of principal components two, three and four of the masked glacier area, the ratio TM-4/TM-5, and the Normalized Difference Snow Index (NDSI). This method avoids problems with sensor saturation, shadowed areas, and discriminates debris mantled ice and ice-marginal water bodies. Combining the thematic map with a high-resolution digital elevation model allows derivation of glacier inventory attributes.