Ice sheet elevation data are collected over Greenland with NASA's Airborne Topographic Mapper (ATM). The data are known as the Greenland Airborne Precision Elevation Survey (GRAPES).
The ATM is a laser altimeter flown on NASA aircraft. The Global Positioning System (GPS) of orbiting satellites is used to navigate the aircraft's autopilot in order to provide precise location information ... for repeat coverage.
The data are collected yearly starting in 1991. The GRAPES data currently available include results from the 1993 mission, with other data to be included soon. Flight trajectory data are available for all years beginning with 1993.
The data collected by ATM form baseline measurements of ice elevation of Greenland. The data will be used in conjunction with the future elevation measurements of the Geoscience Laser Altimeter System (GLAS) instrument onboard the ICESat satellite (to be launched in 2001). Changes in ice sheet elevation measurements provide a better understanding of glacial changes that may be due to global climate change.
For more information, see http://atm.wff.nasa.gov/
[This summary was derived from the pages of the Observational Science Branch at
NASA Wallops Flight Facility. The Observational Science Branch is a division
of NASA's Goddard Space Flight Center Laboratory for Hydrospheric Processes.]