LIGHT DETECTION AND RANGING (LIDAR) DATA PROCESSING AND CLASSIFICATION FOR BATHYMETRIC DEM GENERATION OF PHILIPPINE SHALLOW WATERS

摘要

Benthic mapping plays an important role in effective monitoring and management of underwater resources, especially for a country with many coastal communities and rich aquatic resources such as the Philippines. While conventional bathymetric survey techniques, such as echo sounding, have been widely used to aid in such mapping endeavor, emerging remote sensing technologies which provide a more non-impact approach to bathymetric survey allow the acquisition of more accurate data without causing greater risk of disturbing the underwater resource. Light detection and ranging (LiDAR) technology, which has been used in the Philippines for the past years by the DREAM Program primarily for topographic survey for hazard mapping, is also now being utilized to acquire bathymetric data for shallow waters. This development has extended the application of LiDAR in the country beyond the bounds of its land area by providing data to be used in benthic mapping and aquatic resource extraction. However, unlike in topographic LiDAR data, bathymetric LiDAR cannot be readily used to generate a reliable digital elevation model (DEM) of the underwater surface due to the erroneous elevation of the water bottom point cloud, which is caused by different physical factors brought about mainly by the quality of water. This makes bathymetric LiDAR point cloud rectification and classification an integral process in the generation of vertically accurate bathymetric DEM. Using the survey data collected over Guiuan, Eastern Samar, this paper shows how the DREAM Program processes bathymetric LiDAR data to generate the true water bottom DEM of shallow waters in Philippine coastlines to aid in benthic habitat mapping efforts in the country.