The prime objective of NASA's Arctic Ice Mapping project is to provide accurate ice sheet elevation data for the purpose of change detection. The airborne laser altimetry system ATM, developed by NASA, was successfully used in three missions in Greenland. This paper provides some background information about the ATM system and describes the tests that have been carried out to derive digital elevation models and to extract ice features from the raw data. After transforming the raw data into local coordinate systems, a simple thinning scheme is applied to reduce the redundancy. The digital elevation models are derived either from the original or from the thinned data sets by planar interpolation. Six parallel strips in different areas were bridged together and the resulting elevation model was used to map ice sheet features, such as undulations and lakes.
A lidar system is described that measures laser pulse time-offlight and the distortion of the pulse waveform for reflection from Earth surface terrain features. This instrument system is mounted on a highaltitude aircraft platform and operated in a repetitively pulsed mode for measurements of surface elevation profiles. The laser transmitter makes
use of recently developed short-pulse diode-pumped solid-state laser technology. Aircraft position in three dimensions is measured to submeter accuracy by use of differential Global Positioning System receivers. Instrument construction and performance are detailed.