Estimating the Baseline Error of Wide-Swath Altimeters Using Nadir Altimeters via Numerical Simulation

The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction. These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources. Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies. A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters. Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89, while the correlation coefficient of the length error is 0.85. The sea surface height root mean square error (RMSE) can be reduced from 12.18 cm to 6.45 cm based on the two estimated results. The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation. The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97, which reduces the sea surface height RMSE to 2.88 cm. In addition, the stability of this method is indicated in simulation experiments, which introduce different degrees of sea state errors.