SAR altimeter 3-D localization with combined Delay Doppler Image and spatio-temporal echo similarity

The Synthetic Aperture Radar (SAR) altimeter is an active sensor, which is widely used in satellite microwave remote sensing. It can be also used for geophysical localization by evaluating the similarity between the acquired terrain profile and the prior data. However, typical factors, such as the linear assumption of terrain, high variation of the ground elevation, and wide beam width will degrade the positioning accuracy of localization. In this paper, a 3-D localization method combining Delay-Doppler Image (DDI) and spatio-temporal echo similarity is proposed for the SAR altimeter. Firstly, the signal model of the SAR altimeter for DDI imaging is established. Then, the image-matching algorithm for the DDI is developed to achieve localization in the along-track and height directions. Additionally, spatio-temporal similarity is used to deal with cross-track positioning errors. The main advantage of the proposed method is the reliable 3-D localization, especially for extreme radar configurations, such as large undulations and wide beam width. Experimental results based on both simulated and real data validate the method, showing a significant improvement in localization accuracy.