Research On The Method Of Sea Surface State Inversion Based On Navigation Satellite Reflection Signal

Global Navigation Satellite System(GNSS)can not only provide geolocation and time information,the signals reflected from the earth surface have potential use for various applications including remote sensing of oceans,land,and ice.GNSS-R is a new technique with advantages of full-time,all-weather,high spatial and temporal resolution,low cost,etc.Based on the introduction of the signal structure and related characteristics of GPS and Beidou system,the correlation function of GNSS satellite direct and reflected signals,the Delay-Doppler Map(DDM)generating process are studied.In order to build the theoretical scattering model of GNSS-R sea surface wind field inversion,the related mathematical models are described first,such as wave spectrum model and electromagnetic scattering model,which lays a theoretical foundation for sea state inversion based on navigation satellite reflection signals.The reflected signal of the GNSS has a delay compared to its direct signal,which can be reflected in the chip delay of the pseudo-random code(PRN).In this thesis,altimetry in GNSS-R is carried out by analyzing the chip delay of PRN,and the code altimetry theory model is verified and analyzed with the measured airborne data.Two methods to inverse sea surface wind speed by GNSS-R have been discussed: wind speed inversion method based on measured delay waveform and theoretical delay waveform matching,and wind speed inversion method based on empirical model.The theoretical model and method to inverse sea surface wind speed based on waveform matching have been expatiated systemically in advance,and to analyze the feasibility of wind speed inversion method by waveform matching,the effects of different wind speed,wind direction,satellite elevation angle and receiver height on the delay waveform are simulated.The effectiveness of this method is verified by combining the measured spaceborne data.The BP neural network with strong data fitting ability is introduced into sea surface wind speed inversion to reduce the error when inversion of wind speed in empirical model,and the inversion error is reduced finally.