利用SG平滑滤波优化GNSS-R潮位反演

利用全球导航卫星系统反射(GNSS-R)信号进行潮位反演时,需要对多路径频率进行估计.常规反演方法仅对主频率估计,因此存在数据利用率低、反演结果时间分辨率不足的问题.为解决该问题,本文利用Savitzky-Golay(SG)平滑滤波优化GNSS-R潮位反演.首先,利用Lomb-Scargle周期图(LSP)法提取信号功率的前4个频率f₁~f₄,并反演它们对应的潮位值;然后,利用SG平滑滤波方法提取最佳反演结果;最后,以法国BRST站和MAYG站30 d的数据验证算法的有效性.通过与LSP法和窗口LSP(WINLSP)法进行对比,结果表明:相比LSP法,滤波后BRST站和MAYG站的日均反演值数量分别提升34.3%和19.6%,反演值的最大时间间隔分别减少43.2%和29.4%,RMSE值变化不大;相比WINLSP法,滤波后BRST站和MAYG站的日均反演值数量分别提升24.2%和45.9%,反演值最大时间间隔分别减少25.4%和28.6%,RMSE值均减少了7 cm.总体而言,该方法能够在保证精度的前提下提高反演结果的数量,同时提高了数据的利用率和潮位反演的时间分辨率.

Optimize GNSS-R tide level inversion via Savitzky-Golay smoothing filtering

Multipath frequencies need to be estimated for tide level inversion from Global Navigation Satellite System Reflectometry (GNSS-R) signals.However,conventional inversion methods only estimate principal frequency,which results in low data utilization and insufficient temporal resolution of the inversion results.Here,we use the Savitzky-Golay (SG) smoothing filtering to optimize the GNSS-R tide level inversion.First,the Lomb-Scargle Periodogram (LSP) is used to extract the first four frequencies (f₁-f₄) of signal power,which are then inverted for their corresponding tide level values.Then the SG smoothing filtering is used to extract the best inversion results.Finally,the 30-day data from BRST and MAYG stations in France are used to verify the effectiveness of the approach.The results show that,compared with LSP method,the proposed approach increases the number of daily average inversion values by 34.3% and 19.6%,and reduces the maximum time interval of inversion values by 43.2% and 29.4%,for BRST station and MAYG station,respectively;compared with window LSP (WINLSP) method,the proposed approach increases the number of daily average inversion values of BRST station and MAYG station by 24.2% and 45.9%,decreases the maximum time interval of inversion values by 25.4% and 28.6%,respectively,and reduces the RMSE by 7 cm for both stations.It can be concluded that this method increases the number of inversion results,raises the data utilization and improves the temporal resolution of tide level inversion besides adequate accuracy.