Historic shipwreck study in Dongsha Atoll with bathymetric LiDAR

Dongsha Atoll is a coral reef located in the South China Sea. The surrounding area is characterized by dangerous shoals. Historic shipwrecks mark past human activities. Due to the shallow water and risky navigational conditions in the area, a sonar survey with platforms on the water surface was not feasible. Airborne bathymetric LiDAR, which utilizes green laser for measurement, however, is a proven convenient method for studying shipwrecks around the atoll, particularly in shallow-water areas. At a point density of about 3.5m by 3.5m, four shipwrecks were identified. The bathymetric measurements allow not only the length of the shipwreck to be estimated, but also its height above the sea floor. The full waveform record of the laser reflection also provided information to separate the wreckage from its surroundings. This provides an excellent working environment for marine archaeological analysis, as not only the location, but also the depth and geomorphological information can be assessed in an integrated setting.