Determination of glacier velocities at a large spatial scale from optical satellite archives

In this paper we present a processing strategy to derive glaciers' velocity fields from a complete satellite archive. All possible pairs with a specified time span are formed, submitted to the same preprocessing and matched together to derive velocity fields. All the results are then selected on a pixel-by-pixel basis based on the confidence of the offset-tracking and merged together by computing the median in a spatio-temporal neighboorhood. The method is applied to 206 images covering the Karakoram region and a period of 3 years. This allows us to estimate a velocity for over 90% of the glaciers' area and to reduce the residuals from 9.9m/yr to 2.1m/yr.