Airborne laser and interferometric SAR for mapping heights of glaciers and sea-ice

Abstract

Airborne remote sensing provides a potentially efficient way to monitor and map the cryosphere of the earth, especially in selected areas for climate-related change studies or ground truth for space missions such as IceSat or CryoSat. In this paper we will describe a Twin-Otter based airborne gravity and laser altimetry/scanning system being developed at KMS, and its use for mapping the ice sheet margins of Greenland, as well as initial tests for mapping of sea-ice freeboard and thickness in the Arctic Ocean. The laser system is based on a Riegl laser scanner and Optech laser altimeters, with roll and pitch from a Honeywell INS or a Greenwood IMU. The performance of the system is evaluated against GPS runway surveys and known surface heights, showing fits at the few-din level in general. The system is also to be used for general detailed DEM determination and evaluation in more temporate climates. Sea-ice freeboard surveys have been performed as piggy-back activities on airborne gravity surveys of the Greenland continental shelf regions, with derived geoid information providing an enhanced mean sea surface for ice freeboard estimation. The changing thickness of the Arctic Ocean ice pack is the major driver for ESA's CryoSat mission, planned for launch in early 2004. Over land ice, the emphasis of surveys has been to provide reference DEMs for glaciological studies and evaluation of airborne SAR interferometry. Experiments in East Greenland show that airborne SAR interferometry, as implemented in the DTU-EMISAR system, has the potential to provide ice sheet DEM's at accuracies approaching the 1 m-level r.m.s. in different types of snow facies zones, but with significant radar penetration in the dry-snow zone on the higher levels of the ice sheet.