| In recent years,the disaster caused by the tsunami has caused enormous economic losses and casualties to countries in the world's coastal areas.With the global warming,the melting of polar glaciers has caused sea level to rise.The rise of sea level will intensify the intensity of storm surges and increase the frequency,which will seriously endanger the lives and property of people in coastal areas of China.Therefore,simple and efficient sea level monitoring is particularly important.The use of global navigation satellite system reflection(GNSS-R)for real-time monitoring is one of the more advanced methods.GNSS-R is a technique that uses the variation of waveform,amplitude,phase and frequency of the reflected signals of global satellite navigation system(GNSS)satellites to invert the physical properties of the reflective surface.GNSS-R technology has attracted the attention of scholars at home and abroad because of its unique coverage,wide signal source and relatively low cost.It is widely used in sea surface altimetry research.At present,in the domestic and international GNSS-R sea surface altimetry research,the main methods of code height measurement,phase altimetry and signal-to-noise rate(SNR)observation are used.This article briefly introduces the code height and carrier phase altimetry.The code height is a C/A code using satellite signals.The model is relatively simple,and the device needs to be relatively simple.However,due to the limitation of the length of the C/A code itself,the accuracy of the code measurement is relatively low.The phase altimetry is relatively high in data requirements,which is why the measurement accuracy is relatively high.The GNSS-R single-antenna SNR measurement has become a research hotspot in the field of GNSS-R altimetry due to its simple setup and the need for special custommade reflector antennas and receivers.Aiming at the problem that the current method of inversion of sea surface height using SNR data is relatively simple and has certain limitations,the method of wavelet analysis is proposed to perform shore-based GNSS single-antenna tidal height inversion.Based on the intrinsic connection between the altimetry method based on carrier and SNR observation,the team conducted experiments in Dayangshan,Zhejiang,China,for longterm satellite signal monitoring,and analyzed the SNR data of the processed GNSS-R signals by wavelet transform to get the vertical height of the antenna to the sea surface.At the same time,the wavelet de-noising process is performed on the signal of the noisecontaining source collected in the complex environment.The experimental results show that the altimetry method based on the single-antenna GNSS-R signal SNR can effectively reverse the tidal height,and the high-precision measurement can reach the decimeter level.The main research contents of this paper are as follows:1.A brief introduction to satellite signal capture and tracking.As well as the current major GNSS altimetry methods,high code measurement,phase altimetry,and SNR altimetry.In this paper,we focus on the SNR altimetry.This paper will introduce the SNR signal of GNSS-R for wavelet transform to invert the tidal height of the sea surface.2.The principle of wavelet transform,the importance of wavelet transform parameters and the wavelet parameters used in this paper are analyzed.At the same time,wavelet de-noising is added to improve the accuracy of wavelet transform inversion of sea surface tidal height.3.The experimental team used similar satellite data to carry out LSP analysis to invert the sea level experience,and the accuracy is relatively high to achieve decimeter level accuracy.Before using the wavelet transform to invert the tidal height and long-term monitoring of the sea surface,the reliability of the wavelet transform inversion tidal height is analyzed.The results show that the wavelet transform has high reliability and feasibility.4.After verifying the reliability of the wavelet transform to invert the tidal height,a long-term sea surface height monitoring was carried out in Dayangshan,Zhejiang.During the experiment,the wind speed data of the corresponding sea area was collected to analyze the weather environment receiving the satellite data,and the long-term monitoring of the sea surface height was realized. |
