ICE-SHEET MOTION AND TOPOGRAPHY FROM RADAR INTERFEROMETRY

Both topography and motion information are present in repeat pass ERS- 1 interferograms over ice sheets, We demonstrate that the topography i s separable from the surface displacement field when a sequence of rad ar images are available, If the velocity field is constant over the ti me span of observation, the topography can be derived from differentia l interferograms formed from sequential observations, With this measur ement, a pure displacement field can then be obtained by removal of th e topographic contribution to the interferometric phase at each pixel, Further, we discuss how the vertical and horizontal components of dis placement affect the interferometrically-derived motion field, We illu strate our approach with four successive (3-day repeat) ERS-1 images o f a flow feature in northeastern Greenland.