| Wide -swath altimetry enables extensive, high -resolution, and continuous monitoring of global sea surface height, providing crucial data support for the study of ocean dynamic processes. However, the accuracy of these measurements is significantly affected by various error sources, among which ionospheric delay is a predominant one. Currently, the Surface Water and Ocean Topography (SWOT) mission relies on Global Ionospheric Maps (GIM) for ionospheric delay correction. However, the relatively low spatiotemporal resolution and accuracy of GIM limit its correction capability for the high-resolution SWOT mission. This study fuses data from coastal Global Navigation Satellite System (GNSS) stations, satellite altimetry, and Radio Occultation (RO) in coastal waters. On the basis of vertical height difference compensation and data bias alignment, an improved ionospheric delay correction method for wide -swath altimeters in coastal areas is established based on Helmert’s Variance Component Estimation (VCE). Compared with the single GIM model, which suffers from reduced interpolation accuracy in oceanic regions due to sparse stations, this method utilizes the complementary advantages of multi-source data to effectively fill the gap of high-precision ionospheric information in coastal waters. Evaluation results based on satellite measurements indicate that, compared with the traditional GIM method, the proposed approach reduces the Vertical Total Electron Content (VTEC) error by 1.65 TECU. Consequently, the mean absolute error of the ionospheric delay correction for the SWOT mission is reduced by 0.52 mm, and the root mean square error is decreased by 9.94%. Furthermore, the method exhibits higher stability across latitude zones and time series, significantly improving the data quality for coastal applications. This research validates the effectiveness of VCE in multi-source ionospheric data fusion and provides methodological support for improving the measurement accuracy of the SWOT mission in coastal areas. |
