Multi-Scale Sea Surface Velocity Extraction And Verification From Along-Track Interferometric SAR

Along-track interferometry Synthetic Aperture Radar technology, which is simply called ATI-SAR, was first proposed by America’s Goldstein and Zebker in 1987. The technology has been continuously verified and developed in the following 30 years; and ATI-SAR measurements of the currents have gradually from theory to mature.Technology development of inversion of current field by ATI-SAR is introduced in detail, and significant research progress at home and abroad is presented. Work patterns of ATI-SAR, principles of measuring sea surface current field and so on are also analyzed. And further data selection rules of ATI-SAR established. Then sea surface current field was extracted, separated and verification from the TanDEM-X/TerraSAR-X binary ATI-SAR data using ATI-SAR technology. The main research work done is as following:1. Establish data selection rules. The implementation of ATI-SAR has a variety of modes, such as traditional spaceborne, double receiving antenna, aperture switching and so on. For different working mode for ATI-SAR, there are different requirements for data selection of the current measurement. Therefore, the selection rules of ATI-SAR current measurement data are established. There are two factors considered, that is the length of along-track baseline and temporal decorrelation. The selected data is TanDEM-X/TerraSAR-X formation flying data in the traditional spaceborne mode. The ideal along-track effective baseline distance of the current measurement by ATI-SAR ranges from 14m to 35m, the ideal time delay of two images ranges from 2 ms to 5 ms.2. Extract one dimensional sea surface velocity. Make use of TanDEM-X/ TerraSAR-X binary ATI-SAR data, which is the most promising data during the measurement of current by spaceborne ATI-SAR. Data processing of current extraction using this data is mainly in Germany Aerospace Center (DLR) and the University of Miami. Data processing of extracting the one dimensional sea surface velocity is implemented. The currents near Orkney Islands north of Scotland are successfully extracted, and the obtained one dimensional sea surface velocity range from-0.32m/s to 1.94m/s. The research results show that the ATI-SAR data processing can effectively extract one dimensional sea surface velocity.3. Separate and verify the current velocity. The extracted current velocity using ATI-SAR technology is actually a variety of different scales’velocity superposition sum. In order to accurately extract each component of the current velocity, it is necessary to separate the extracted current velocity. The main work of verifying the accuracy of the extraction and separation of the current velocity is as following. Firstly, the line of slight current velocity, which called Doppler velocity obtained by ATI-SAR technology, and the results obtained by Doppler centroid analysis technology have been compared; the results show that both are well consistent. And then, using SAR image spectrum, combined with the relationship between wave propagation and the water quality point movement, calculated the velocity component of the study area generated by ocean waves, and verified the accuracy of the current velocity caused by ocean waves in the separation of ocean surface current velocity. Finally, the current extraction algorithm is applied to another pair of binary ATI-SAR data, located at the southwest near the island of Islay, and the obtained one dimensional sea surface velocity range from-1.38m/s to Om/s, further verified the reliability of the extraction algorithm.