Remote Sensing of Glacier Fluctuations Using Landsat Data: Lessons Learned


John L. Dwyer
Hughes STX Corp.1, EROS Data Center, Sioux Falls, SD 57198


Ten Landsat multispectral scanner (MSS) and thematic mapper (TM) images acquired between 1978 and 1991 were analyzed to map the positions of more than 75 ice fronts for tidewater and land-terminating glaciers in East Greenland. The images had different internal geometric characteristics due to variations among the individual satellite orbital geometrics and the types of processing applied by the satellite ground receiving stations. The images were coregistered to a single Landsat TM reference scene with a 30 meter by 30 meter pixel resolution, and error budgets associated with image registration were formulated. Scenes were individually contrast enhanced as false-color composites and integrated into a geographic information system (GIS). Softcopy digitizing tools within the GIS were used to compile maps of glacier basins and time-step overlays of ice front positions from which planimetric areal changes to glacier extents were calculated. The changes to glacier extent were then quantified to include uncertainties attributable to misregistration errors. Automated image cross-correlation techniques were applied to two Landsat TM images acquired in July and September of 1989 to derive surface velocity estimates for nine large glaciers in the study area.

The delineation and quantification of changes to land-terminating glacier extents were significantly compromised by the inability to consistently identify the boundary of ice fronts mantled with debris The spatial resolution of the images further precluded interpretation of surface morphological variations in the glacier terminus areas that might otherwise have aided inferences of the ice front positions. The lack of sufficient radiometric calibration data specific to the satellite sensors and ground processing systems also precluded attempts to spectrally discriminate changes in surface reflectance at the ice-moraine contacts. The contrast between highly reflective ice-snow and dark sediment often contributed to "memory effects" in the spectral response at the satellite sensors such that the discrimination of surface reflectance variations were "blurred". Increases in the extent of ice-snow cover were more readily discernible than states of regression or stagnation.

1. Work performed under U.S. Geological Survey contract 1434-92-C-40004 [an error occurred while processing this directive]