Repeat track SAR interferometry

Repeat track interferometry can detect millimetre scale surface displacements on a wide area basis. This, in combination with elevation mapping capabilities, is important in many geoscience studies. Glacier dynamics studies, for example, has previously to a large extend relied on point measurements of ice motion and elevation.
In 1996 a first version full processing chain including pre-processing of radar and navigation data, SAR focusing, baseline estimation, interferometric phase inversion, and geocoding has been established. A unified approach for aircraft and satellite data was adopted.
For the Storstrømmen Glacier, North East Greenland, the full vector flow field and the elevations was derived, by using ascending and descending ERS imagery in combination with a surface parallel flow assumption.
The airborne EMISAR L-band repeat track interferometry data acquired on two consecutive days in august 1995 have been processed and the data looks promising for extraction of velocities; not yet demonstrated with any airborne system. The uncertainties on the time varying spatial baselines have been reduced from the meter level to some centimetres. However, a method for estimating the spatial baseline over rough terrain still needs to be established.
In 1997 the processing chain for ERS-1/2 was further refined, so that operator intervention is required only for reading raw data from tapes, and for composition and execution of a script with scene identifications. The benchmark for generating an interferogram from to raw ERS-1/2 scenes is 26 min. Airborne repeat track SAR data were acquired over the Nioghalvfjerdsfjorden glacier, Northeast Greenland for the land ice studies. (Related projects - see: www.dcrs.dtu.dk).