Accurate Refraction Correction—Assisted Bathymetric Inversion Using ICESat-2 and Multispectral Data

Changda Liu,Wenjun Meng,Xinghua Zhou,Qiuhua Tang,Jie Li,Wenxue Xu,Jiawei Qi

doi:10.3390/rs13214355

Abstract

Shallow-water depth information is essential for ship navigation and fishery farming. However, the accurate acquisition of shallow-water depth has been a challenge for marine mapping. Combining Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) bathymetry data with multispectral data, satellite-derived bathymetry is a promising solution through which to obtain bathymetric information quickly and accurately. This study proposes a photon refraction correction method considering sea-surface undulations to address errors in the underwater photons obtained by the ICESat-2. First, the instantaneous sea surface and beam emission angle are integrated to determine the sea-surface incidence angle. Next, the distance of photon propagation in water is determined using sea-surface undulation and Snell’s law. Finally, position correction is performed through geometric relationships. The corrected photons were combined with the multispectral data for bathymetric inversion, and a bathymetric map of the Yongle Atoll area was obtained. A bathymetric chart was created using the corrected photons and the multispectral data in the Yongle Atoll. Comparing the results of different refraction correction methods with the data measured shows that the refraction correction method proposed in this paper can effectively correct bathymetry errors: the root mean square error is 1.48 m and the R2 is 0.86.

Highlights

Shallow waters around nearshore environments and islands are closely related to biological survival and human economic activities
The maximum depth obtained by the ICESat-2 was about 18.5 m, the mean value of sea-surface fluctuation was 0.18 m, and the mean value of sea-surface slope was 8.2◦
We developed a refraction correction method taking into account seasurface undulation to produce accurate bathymetric photons and mapped the bathymetry pattern of the Yongle Atoll by coupling high-precision photons from ICESat-2 and highresolution Sentinel satellite imagery

Summary

Introduction

Shallow waters around nearshore environments and islands are closely related to biological survival and human economic activities. Detailed bathymetric data are the basic geographic information necessary to utilize the resources in these areas [1,2]. It is necessary to acquire the data on a large scale and with high precision. Obtaining bathymetry in these regions for marine mapping is difficult. Multibeam and side-scan sonar systems feature poor reachability and narrow bandwidth because of shallow-water depths [3]. Water depth does not limit the airborne LiDAR bathymetry system [4,5], but its equipment is expensive, and its market penetration rate is low. Because of its sensor accuracy, the depths obtained by optical remotesensing bathymetry inversion are limited [1,6,7]

Methods

Results

Conclusion