Satellite Glaciology - Satellite and remote sensing methods

Landsat images in the visible and near infra-red wavelengths clearly depict many of the large- and small-scale features of the surface. The intensity of the reflected radiation varies with the aspect and magnitude of the surface slope to reveal the surface topography. The multi-channel nature of the Landsat data are exploited to distinguish between different surface types through their different spectral signatures, e.g. bare ice, glaze, snow, etc.

Additional information on surface type can be gained at a coarser scale from other satellite-borne sensors such as the ESMR, SMMR, etc. Textural enhancement of the Landsat images reveals the surface micro-relief. Features in the enhanced images are compared to ground-truth data from the traverse surveys to produce a classification of the surface types across the images and to determine the magnitude of the surface topography and micro-relief observed.

The images can then be used to monitor changes over time. Landsat imagery of the Antarctic ice sheet and glaciers exhibit features that move with the ice and others that are fixed in space. Two images covering the same area but acquired at different times are compared to obtain the displacement of features.

Where the time lapse is large, the displacement of obvious features can be scaled from photographic prints. When the two images are co-registered finer features and displacements can be resolved to give greater detail. Remote sensing techniques can be used to investigate the dynamics and surface characteristics of the Antarctic ice sheet and its outlet glaciers.

This paper describes a methodology developed to map glacial movement velocities from LANDSAT MSS data, together with an assessment of the accuracy achieved. The velocities are derived by using digital image processing to register two temporally separated LANDSAT images of the Denman glacier and Shackleton Ice Shelf region. A derived image map is compared with existing maps of the region to substantiate the measured velocities.

The velocity estimates from this study were found to correspond closely with ground-based measurements in the study area.