Glacier Applications of Erts Images

Abstract

Abstract The ERTS satellite’s sun-synchronous orbit covers the entire Earth horn lat. 81° N. to 81° S. every 18 d at approximately 10.00 a.m. ground time. The scanners on board have continued to relay images to Earth from the launch on 23 July 1972 to the present (summer 1974). Images from four spectral bands (0.5-1.I μm), with ground resolution of about 100 m. cover an area 185 km on a side. The resulting images have proved to be very useful for collecting certain basic data from glaciers. Long-term surface velocities are readily determined by comparison of recent ERTS images with maps that have been produced from earlier data. Images have been used 10 measure velocities on the Malaspina Glacier over a 10 year period, surge displacements on the Lowell, Tenas Tikke. and Tweedsmuir Glaciers and Lednik Medvezhiy, and velocity at the margin of the Hubbard Glacier. Many surging glaciers are readily identifiable on (he images. Coverage from the satellite will allow surging glaciers to be identified world-wide which may help glaciologists to understand their peculiar geographical distribution. Images of large glaciers taken under conditions of low sun angle and complete snow cover show previously undetected subtle slope changes which can be interpreted as dynamic How features or reflections of subglacial topography. ERTS imagery is providing new glacier data for several reasons: very large areas are covered repetitively with sufficient consistency to show subtle tonal changes, conditions of maximum and minimum snow cover, subtle morphologic features at low sun angle, and changes in position of glaciers.