Retrieval of Nearshore Bathymetry around Ganquan Island from LiDAR Waveform and QuickBird Image

Abstract

Optical remote sensing is an effective means of water depth measurement, but the current approach of mainstream bathymetric retrieval requires a large amount of onsite measurement data. Such data are hard to obtain from places where underwater terrains are complicated and unsteady, and from sea areas affected by issues with rights and conflicts of interest. In recent years, the emergence of airborne light detection and ranging (LiDAR) provided a new technical means for field bathymetric survey. In this study, water depth inversion was carried out around an island far from the mainland by using remote sensing images and real LiDAR waveform data. Multi-Gaussian function fitting was proposed to extract water depth data from waveform data, and bathymetric values were used as control and validation data of the active and passive combination of water depth inversion. Results show that the relative error was 5.6% for the bathymetric retrieval from LiDAR waveform data, and the accuracy meets the requirements of ocean bathymetry. The average relative error of water depth inversion based on active and passive remote sensing was less than 9%. The method used in this study can also reduce the use of LiDAR data and the cost, thus providing a new idea for future coastal engineering application and construction.

Ocean Remote Sensing Techniques and Applications: A Review (Part II)

“…The shipborne methods, such as echo sounding, are relatively efficient for underwater studies [274]. However, these methods are also limited over large remote ocean areas mainly due to the high cost [297,298]. Additionally, the Field surveys are time-consuming, expensive and have accessibility issues [277,296].…”

“…The shipborne methods, such as echo sounding, are relatively efficient for underwater studies [274]. However, these methods are also limited over large remote ocean areas mainly due to the high cost [297,298]. Additionally, the applicability of this technique is negatively affected by technological restraints and environmental conditions in coastal regions [299].…”

“…Optical multi-spectral satellite-derived bathymetry is based on the statistical relationships between the in situ measurement of water depth and image pixel values. The blue spectrum (0.45-0.52 µm) can be used for optically sensing bathymetry because of its high penetration capabilities [297,298] (see Figure 12). During the past decades, a vast number of algorithms varying from empirical (e.g., band rations, logarithmic-transformed models, and ML models) to physics-based models have been developed for bathymetric mapping using optical satellite imagery [302,304,310].…”

Challenges and Opportunities in Lidar Remote Sensing

“…Morsy et al, (2017) demonstrated that the combination of building height and spectral information achieved a clearly higher accuracy than elevation data alone in mapping urban land cover. Retrieval of bathymetry using a single spectral channel is a wellestablished lidar application but opportunities for innovations remain significant, such as the integration of mono-spectral lidar with passive multi-spectral images to map coastal water (Zhang et al, 2019). Imaging, multi-spectral lidars combine differential water absorption with range measurements to map coastal waters and the land/water boundary very accurately (Morsy et al, 2018)…”