Ice velocity determined using conventional and multiple-aperture InSAR

We combine conventional Interferometric Synthetic Aperture Radar (InSAR) and Multiple Aperture InSAR (MAI) to determine the ice surface velocity on the Langjokull and Hofsjokull ice caps in Iceland in 1994. This approach allows the velocity of the 20 principal ice cap outlet glaciers to be fully resolved. We show that MAI leads to displacement estimates of finer resolution (15 versus 150 m) and superior precision (5 versus 15 cm) to those afforded by the alternative technique of speckle tracking. Using SAR data acquired in ascending and descending orbits, we show that ice flows within 15° of the direction of maximum surface slope across 66% of the ice caps. It is therefore possible to determine ice displacement over the majority of the ice caps using a single SAR image pair, thereby reducing errors associated with temporal fluctuations in ice flow.