Shore-based GNSS For Tide Level Monitoring And Tide Coefficient Extraction

The rise of sea level caused by global warming has brought great challenges and threats to human survival and economic development in coastal areas,so it is very important to monitor it.Monitoring sea-level change not only plays an important role in the study of climate,but also helps to predict the social and economic consequences of sea-level rise.As an important factor of ocean tide change,it is necessary to extract tide coefficient and analyze tide model.With the development of GNSS research and application,GNSS-IR technology based on multi-path effect has become a new tide level monitoring method.However,at present,there are few researches on the extraction of tidal coefficients in coastal areas by using GNSS-IR technology in China.In order to further expand the application space of GNSS-IR technology in the field of ocean tides,this paper uses the DSPU station on the roof of the tide chamber in Shipu port,Shipu Town,Zhejiang Province,and the DSPU station on the roof of the tide chamber in huashengton state,USA The tide level data obtained from SC02 station of GNSS observation station on the Bank of harbor harbor are monitored and analyzed for tide level and tidal coefficient.The comparison experiment is carried out based on the results of harmonic analysis of measured tide level of tide gauge station.The accuracy of the global ocean tide models tpxo6.2,tpxo09 and dtu10 are evaluated.The main contents and innovations of this paper are as follows:1.On the basis of in-depth study of the basic principle of GNSS-IR technology used in tide level monitoring,the characteristics of GNSS signal-to-noise ratio are analyzed,and the daily and monthly average sea surface obtained by GNSS-IR with different frequencies(L1,L2)are tested.The second,third,fifth and EMD methods are used to extract the interference signal.The results show that different frequency of GPS signal can be applied to the real-time monitoring of tide level,L1 is slightly better than L2.The second order and EMD methods can extract the interference signal of SNR accurately.2.The results show that the retrieved tide level from GNSS-IR is in good agreement with the measured tide level of tide gauge station,the average deviation between the two stations is about 20 cm,and the correlation coefficient is better than 0.97;the retrieved tide level from GNSS-IR and the measured tide level of tide gauge station is better than 0.97 The coefficient is basically the same;the mean value of the difference between the results of SC02 station and the results of tide gauge station is 2.93 cm,the RMS of the difference is 3.57 cm,and the correlation coefficient is better than 0.98.It can be seen that the tide level obtained by long time series is more accurate.3.Combining GNSS-IR technology with traditional harmonic analysis package t-tide,this paper evaluates the accuracy of three tide models TPXO6.2,TPXO9 and DTU10.The results show that there is little difference between the amplitude and the late angle obtained from the inversion of tide level on the shore base of GNSS-IR and the amplitude and the late angle obtained from the corresponding tide station.The tide coefficient obtained from the inversion of tide level on the GNSS station is consistent with the tide coefficient calculated from the tide model It has a high accuracy in obtaining tidal coefficients,and can effectively supplement the offshore areas where the satellite altimetry accuracy is not high.In addition,t-tide and the improved s-tide harmonic analysis package are compared and analyzed,and the results show that they are equivalent.