Insar Radargrammetry : a Solution to the Phase Integer Ambiguity Problem for Single Interferograms

The interferometric phase in a SAR interferogram may only be represented in the range 0-360 degrees, leaving an unknown integer ambiguity representing the number of extra whole wavelengths travelled during the imaging at the second antenna. This makes it impossible to solve for the precise baseline components from the interferogram alone. In this paper, the InSAR geometry is re-examined using a radargrammetric approach that proposes the use of space triangulation to determine target position and height. From this approach, a solution to the phase integer ambiguity is proposed that requires only coarse, sparse ground control to enable the 3D location of all points within an interferogram to be determined. Furthermore, the solution implies that precise differential InSAR may be applied over all terrain types without the use of an accurate DTM. This solution allows further automation of the technique, enables fast responses to events in remote, unmapped areas and negates the requirement to build up a vast map archive to support a global InSAR mission. The results are illustrated using experimental data from the GB-SAR facility at the University of Sheffield.