The Glaciers Climate Change Initiative : Algorithms for creating glacier area , elevation change and velocity products

Glaciers and their changes are increasingly monitored from a wide range of satellite sensors. Due to the often remote location of glaciers in inaccessible and high-mountain terrain, satellite observations complement ground-based measurements very well. Furthermore, satellite data provide observations of glacier characteristics that are difficult to monitor from ground. In the Glaciers_cci project three of these well-observable characteristics are investigated in detail: glacier area, elevation changes (ELC) and surface velocity (VEL). We use optical sensors to automatically derive area, digital elevation models from two points in time and repeat altimetry for ELC, and optical and microwave imaging sensors for VEL. For the latter, the two sensor types again provide complimentary information in regard to their spatio-temporal coverage. While some products can be generated largely automatically (ELC from altimetry and VEL), the others require interaction by the analyst. Largely based on round robin experiments for each of the products, we suggest in this contribution the most suitable algorithms for product creation and describe them here along with remarks on their practical implementation. In many cases the details on the latter are even more important for creation of high-quality products than the basic algorithm itself.