Refraction and coordinate correction with the JONSWAP model for ICESat-2 bathymetry

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) provides a new measurement strategy thanks to an advanced topographic laser altimeter system that uses photon counting technology for highly accurate nearshore bathymetry and underwater topographic mapping. In this technique, however, the refraction of water leads to a displacement of the position of the photons on the seafloor, which reduces the accuracy of the measurement. To overcome this problem, a novel refraction correction approach constructed on the ray tracing and JONSWAP spectrum is proposed in this study for ICESat-2. In this method, the coordinate compensation of each seafloor photon was applied in the WGS84 coordinate system to improve the positioning precision of seafloor photons. Experimental results showed that the proposed refraction correction method could precisely reduce the displacement of each photon on the seafloor. For the displacement elimination and coordinate compensation, the highest accuracy of photon counting measurements for the seafloor profile could reach −0.29 m of bias and 0.42 m of root mean square error in our study area. Finally, the influence of the Earth’s curvature on the refraction correction was analyzed in detail, revealing that curvature displacement ranged in value between −5 and −6 power. Therefore, it was considered negligible in terms of its effects on underwater topography and nearshore bathymetry mapping.