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Validation of Maritime Spectral Features

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posted on 2023-08-04, 15:59 authored by Matthew J. Hubler

In 1991 Hasselmann and Hasselmann developed a general technique to build synthetic aperture radar (SAR) spectra from scans of the ocean surface; however these techniques were verified on older equipment. The algorithms process a SAR spectrum from an ocean spectrum, an inversion from SAR spectrum to ocean spectrum, and determine the threshold of the azimuthal cutoff. Originally designed for platforms that have since fulfilled their missions, the question remains as to whether the algorithms are valid with newer systems such as TerraSAR-X operated by German Aerospace Centre (DLR). One of the larger differences that may skew data analysis by these algorithms is that TerraSAR-X has much finer resolution, pixels being on the scale of 5-10 meters, while older satellites returned images with pixel scaling on the order of kilometers. The finer pixel scaling allows for more detail to be recovered and analyzed, specifically the individual waves on the ocean surface become visible. To that end, algorithms developed for older satellites will be employed on data collected from TerraSAR-X and compared to ground truth data in order to assess the validity of existing algorithms. During the course of the validation, several sets of code, written in Matlab, will be employed and discussed, each providing a different approach, more focused results. In aggregate a clearer picture will emerge describing the accuracy that older algorithms have with newer machinery. The imagery data, being satellite borne, comes with individual collection geometry that needs to be addressed in the processing as well, currently through parsing the accompanying metadata. Since the initial purpose of TerraSAR-X involved imaging over landmasses, the codes must be able to interface with other programs in our research group to contribute broadly to our scientific mission. The determination that these algorithms indeed work with newer systems and the validation of an azimuthal cutoff demonstrate that little fine tuning of older algorithms is needed. While the Hasselmann algorithms become cumbersome to use, a new approach to the algorithms yield useful quantifiable measurements. Thus combination of these new algorithms, buoy ground truth data, and more recent SAR technology deliver an immensely powerful analytical tool. The eventual result of these algorithms would apply to meteorology, commercial shipping, disaster planning and recovery, ecology, and a vast assortment of other fields that would seek the wind patterns in open ocean scenes.





Degree awarded: M.A. Mathematics and Statistics. American University


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