Validation of the Height Estimation from a Multibaseline Approach in Millimeterwave Interferometric SAR by Laser Data

摘要

Synthetic Aperture Radar (SAR) at millimeter-wavelengths offer a range of advantages over classical microwave frequencies. Among those are compact system design and short aperture lengths for a given cross-range resolution which, together with lower importance of image distortions, make this sensor especially appropriate for UAV-based reconnaissance applications. Interferometric SAR allows to sense the height of natural and man-made objects and may also be implemented at mm-wave frequencies. Due to the short wavelength the interferometric baselength to yield a certain height estimation is smaller by the ratio of wavelengths if compared with InSAR at microwave frequencies. Unfortunately the unambiguous height interval is reduced by the same amount. To solve this problem a hardware approach was developed, introducing a linear multiple antenna arrangement with increasing baselengths going from narrow to wide. The narrowest is assumed to be unambiguous in phase. With this coarse interferogram the algorithm starts and unwraps the interferogram with the next wider baseline. The result is a refined unambiguous interferogram, which is now used as new starting point for the algorithm. This process is repeated consecutively until the interferogram with highest precision is unwrapped. On the expense of this multi-channel-approach the algorithm is relatively simple and robust, and even the amount of processing time is reduced compared to other competing ones. To validate this approach a scene measured previously with the InSAR was scanned with an airborne laser-system to get elevation data as a reference. In this paper we show the results of tests on a reference scene, together with the laser data. The correlation between both data sets demonstrates the capability of the approach.