Technical Studies


The Establishment of Digital Bathymetric Model of Dongsha Atoll with Bathymetric Lidar

The primary study area of this project is Dongsha Atoll. The second study area is Penghu. The major objective of this study is to map near coastal and shallow water area with airborne bathymetric lidar. After extensive investigation and negotiation, NCTU signed contract with Geomatics Data Solutions and Pelydryn in May 2010. The aircraft selected is an SA-226T and the scanning instrument is an AHAB HawkEyeⅡ. This project has successfully collected 415 square kilometer laser scanning data in Penghu at the density of 3.5m x 3.5m. There are 124 bathymetric flight strips and 118 topographic flight strips. In total, there are 75,804,547 measurements. The surveyed area in Dongsha Atoll includes about 450 square kilometers with 3.5m x 3.5m density, and 20 square kilometers with 2m x 2m density. The number of 3.5m x 3.5m density flight strips is 229. Among them, 18 have topographic measurements. The number of all measurements is 45,022,204. There are 26 strips and 1,790,361 measurements for the 2m x 2m density. The coordinate system used for surveying is TWD97 and the height system is ellipsoidal height. Both the interior and exterior validation schemes are applied for the accuracy analysis. For the interior validation, the overlap from cross flights and the sidelap from the parallel flights are used. Single beam sonar survey is conducted after the airborne bathymetric lidar mission. 14.5 square kilometers were surveyed in Dongsa area and 12.3 square kilometers for the Penghu area. Also conducted in this project include the collection of existing charts, establishing a control surveying network in Dongsha island, and a continuous logging tidal station. Tidal analysis with 1096 days observation for Penghu and 494.37 days observation for Dongsha were performed. Two counts of invention, eight academic articles, and one poster paper were published. The data collected in this project and the digital bathymetric model generated, could provide vital information for both the governmental development plan and academic researches. Meanwhile, the strategy of implementing future projects to fully make use airborne bathymetric lidar technology may be developed based on the experiences learnt.