ICESat Elevations in Antarctica Along the 2007–09 Norway–USA Traverse: Validation With Ground-Based GPS

The 2007-09 Norway-USA Traverse of East Antarctica collected dual-frequency Global Positioning System (GPS) data at 5-s intervals on two of the traverse vehicles. The traverse covered 2400 km from the coast to the vicinity of the Amundsen-Scott South Pole Station in 2007-08, and a 2600 km route from the South Pole to the coast in 2008-09. Side traverses were also conducted in 2008-09, for a total of over 10 000 km of GPS data between the two vehicles. We use precise point positioning to post-process our single receiver kinematic GPS data. Analysis of data obtained while the vehicles were stationary shows individual solutions are accurate to ca. 1 cm horizontally and 3 cm vertically. We compare our GPS elevations with those determined by the National Aeronautics and Space Administration´s Ice, Cloud, and Land Elevation Satellite (ICESat), a space-based altimeter designed to measure ice elevation. ICESat accuracy is evaluated by cross-over analysis; mean differences calculated between dh/dt-corrected ICESat data and GPS-derived surface elevations for two vehicles and two traverse seasons range from -12 to -2 cm, within ICESat´s stated goal of ±15 cm, while 1-σ values of the same data imply that ICESat´s precision is ca. 15.8 cm.