## 5 Discussion
The SGDR data are no longer reliable in the area within 12 km offshore, and the correlation coefficient and RMS worsen dissimilarly. Although the reprocessing results are influenced by the waveform noise caused by coastal land, the reprocessing results still show good performance, and the mean values of the correlation coefficient and RMS are 0.89 and 45.1 cm, respectively. Figure 14: Height comparison of the ASSH between HY-2B pass 323 and pass 196 with tide gauge data. (\(x\)-axis is the number of cycle. The \(y\)-axis is the unified value of sea surface height. The left is the comparison within the range 10 km offshore for pass 323, the right is the comparison within the range from 10 km to the island for pass 196). Figure 16: Correlation coefficient (**top**) and RMS (**bottom**) of the ASSH data comparing with tide gauge data of Subic Bay Station for HY-2B pass 196; (\(x\)-axis is the along-track latitude of the nominal tracks. The shaded light grey indicates the land and the deep shadow represents coastal island). Figure 15: Correlation coefficient (**top**) and RMS (**bottom**) of the ASSH data comparing with tide gauge data of Subic Bay Station for HY-2B pass 323; (\(x\)-axis is the along-track latitude of the nominal tracks. The shaded light grey indicates the land). Figure 16 shows the correlation coefficient and RMS of the ASSH data against the tide gauge data in HY-2B pass 196. As shown in Figure 16, the quality of the reprocessing result is significantly improved compared to the SGDR data. The correlation coefficient of the reprocessing result has a steady and overall enhancement, and the mean values of the correlation coefficient and RMS are 0.90 and 29.3 cm in the range from 120.2\({}^{\circ}\)E to 120.125\({}^{\circ}\)E. In contrast, the mean values of the correlation coefficient and RMS of the SGDR data are 0.89 and 30.0 cm, respectively. This is attributed to the effective trailing edge processing of waveform retracking, which can not only address the distortion of the waveform but also weaken the influence of trailing edge noise. In the range of 12 km offshore, although the correlation coefficient and RMS of the reprocessing results are better than those of the SGDR data, they fluctuate due to the observation mode conversion of the altimeter, and the mean values of the correlation coefficient and RMS for the reprocessing data are 0.84 and 33.0 cm, respectively. Within the range 5 km offshore (120.125\({}^{\circ}\)E to 120.09\({}^{\circ}\)E), the data quality of the SGDR products worsens as the shoreline approaches, and the reprocessing results show high quality, with mean values of the correlation coefficient and RMS of 0.92 and 36.2 cm, respectively, which is similar to the open sea observations. This also illustrates that the waveform retracking provided in this study is good at dealing with the waveform influenced by some small coastal 'pollution', such as coastal islands. According to the above analysis, the reliability and accuracy of the HY-2B altimetry data processed by waveform retracking proposed in this study are better than those of the standard SGDR data in coastal areas. In the range beyond 20 km from the shoreline, the correlation coefficient and RMS of the reprocessing results are slightly better than those of the SGDR data, which indicates that the waveform retracking proposed in this study is also suited to open sea observations. Within 15 km offshore, the precision of SGDR data decreases seriously, while the reprocessing results are still fine advancing the application potential of HY-2B satellite altimetry data in coastal areas.