Improving Water Level Retrieval Accuracy of GNSS-IR Based on Ionospheric Refraction Correction Optimization Method

The global navigation satellite system-interferometry reflectometry (GNSS-IR) has been considered commonly to be reliable for retrieving water level. However, the GNSS signal undergoes refraction phenomenon when it passes through the ionosphere. Refraction phenomenon makes the elevation angle deviates from the true value and reduces retrieval accuracy. Therefore, we constructed ionospheric refraction correction optimization method (IRCOM) to correct the angle error caused by ionospheric refraction. The correction formula takes the original elevation angle as an input and corrects the elevation angle by electron density. In order to prove the validity of IRCOM, we conducted experiments with raw data from six stations. The retrieval results show that the average root mean square error (RMSE) reaches 14.67 cm and the average Pearson’s correlation coefficient (PCC) reaches 88.19%. Meanwhile, the RMSE of IRCOM retrieval results is 4.91% lower than GNSS-IR on average, and the PCC of IRCOM retrieval results is 12.13% higher than GNSS-IR on average. The experimental results show that IRCOM can accurately retrieve water level with improved accuracy compared to GNSS-IR.