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Detall de la Tesi
| Sea Surface Determination Using GNSS Reflected Signals
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| Resum
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The Global Navigation Satellite Systems (GNSS) are large, stable and calibrated sets of spaceborne L-band microwave transmitters with very well characterized properties. They provide global and permanent coverage as required by the meteorological, oceanographical and climate scientist. All these features make the GNSS signal an appropriate candidate to be an excellent source of opportunity for bistatic monitoring of the Oceans' surface.
The dissertation 'Sea Surface Determination Using GNSS Reflected Signals' tackles the question of how the GNSS signal scattered off the ocean surface can be used to obtain geophysical information about the sea-air interface. The focus is put on the retrieval of the surface roughness and/or the wind.
The thesis defends a scatterometric approach where the distribution of the scattered power crosswise the illuminated area is used to infer the roughness of the surface. The distribution or mapping is achieved by parceling the sea area in cells whose scattered signal has different delay and frequency properties. This information is gathered in anobservable called waveform.
The structure of the thesis has been divided in three main parts: (a) the modeling of the scattered GNSS signal (GNSSr); (b) the feasibility study; and (c) the experimental validation.
The scatterometric GNSSr forward and backward models are presented. The former generates the waveform of the reflected signal as a function of the geometry of the scattering, instrumental parameters, as well as the roughness of the sea surface. The backward approach proposed at this level tries to infer the sea surface roughness characteristics of the illuminated area through the inversion of the waveform.
The expected performance of the scatterometric-GNSSr system is analyzed as a first order examination of its capabilities in terms of resolution and accuracy of the wind measurements. The aim of this part of the study is to determine how precisely can the wind be measured by the GPSr techniques proposed in the backward model, as wellas how can these observations cover the Oceans.
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