海南岛沿岸海域水体漫衰减系数光谱分析及LiDAR测深能力估算

Analysis of Diffuse Attenuation Coefficient Spectra of Coastal Waters of Hainan Island and Performance Estimation of Airborne LiDAR Bathymetry

机载激光雷达测深是近年来蓬勃发展的主动式水深测量方法,能够快速精准地获取近岸水深和水下地形,特别是对于浅海、岛礁等船只无法达到的区域具有显著优势。而机载激光雷达系统的测深能力主要受到水体浑浊度的影响。激光测深实验中对实验区域的水体浑浊度研究将有助于实验方案的设计。以中国海南岛沿岸海域为例,研究了该海域水体浑浊度和机载激光雷达测深系统CZMIL(coastal zone mapping and imaging LiDAR)测深能力之间的关系,建立了运用水体漫衰减系数估算机载激光雷达测深系统测深能力的算法。首先分析并确定了实验区域的漫衰减系数K_d(490)反演算法;其次,运用该区域实测光学数据建立了漫衰减系数K_d(490)和K_d(532)之间的数值关系;接着总结了K_d(532)和CZMIL系统最大测深值之间的关系;最后运用MODIS数据合成了海南岛沿岸海域在CZMIL系统海道测量模式下的测深能力空间分布图,重点分析了海口和陵水附近海域的最大可测水深分布情况。为海南岛沿岸海域开展激光测深实验提供了参考和依据。

Airborne LiDAR bathymetry is an active bathymetry method developed in recent years,which can quickly and efficiently obtain the water depth and underwater topography,especially plays an important role in surveying on shallow water and islandreefs where ships are not accessible.In general,the maximum detectable water depth of airborne LiDAR bathymetry systemis mainly affected by the turbidityof water.Therefore,a detailed study of water turbidity of the experimental regionin advance will contribute to design the experimental scheme.In this paper,taking the coastal waters of Hainan Island in South China as an example,we studied the relationship between turbidity of water and the bathymetry performance ofan airborne LiDAR bathymetry system named CZMIL(coastal zone mapping and imaging LiDAR),and presented an algorithm that can estimate the spatial distributionof maximum CZMIL detectable water depth in the coastal waters of Hainan Islandby using the values of diffuse attenuation coefficient of sea water.Firstly,we studied the K d(490)inversion algorithm in the experimental water region.Secondly,the relationship between the diffuse attenuation coefficient K d(490)and K d(532)was established by using the measured optical profiledata in this region.Then,the relationship between the diffuse attenuation coefficient K d(532)and the maximum CZMIL detectable depth was summarized.Finally,the spatial distribution of K d(532)and maximum CZMIL detectable depth in the coastal waters of Hainan Island were retrieved by using MODIS data.What’s more,the distribution of maximum CZMIL detectable depth in the coastal waters of Haikou City and Lingshui City are analyzed emphatically.The results provide a reference for the LiDAR bathymetric operation in the coastal waters of Hainan Island.