Summary
Heard Island is a volcanic island, which is 80% ice-covered, situated in the southern Indian Ocean. Measurement of the variation in the mass and length of Heard Islands glaciers over time provides valuable data related to climatic change in a region mostly devoid of such information. A combination of line maps and SPOT satellite multi-spectral images from various epochs is used to determine the glacier boundaries. Problems encountered in the interpretation of source material and preparation of the data sets are discussed. A method is devised to readjust the digital version of the historic line maps to a reference datum based on one of the images while preserving the geometric integrity of the geographic features. A combination of an Image Processing System and a Geographic Information System is used in the analysis of the boundaries and registration of the data sets. Comparison of the glacial boundaries indicates that significant retreat has occurred on Heard Island in the period 1980-1988, notably on the north and east coasts where the glaciers terminate in lagoons or on an outwash plain. Significantly, the retreat of some of those glaciers is comparable in magnitude to that reported by other workers for the interval 1947-1980. The image data establish the first reference baseleine for all glaciers of the major ice-covered area for use in systematic monitoring by satellite in the future.