Drone derived orthomosaic and digital surface model of Béchervaise Island (December 2024)

Orthomosaic and Digital Surface Model (DSM) generated from drone derived imagery collected on the 05th of December 2024 (20241205 091913 UTC) by Dr Gwil Price and Ben Viola.A DJI M300 RTK drone fitted with a DJI Zenmuse P1 camera with 35mm lens was used to collect mostly nadir photographs, at a height of ~ 80.6 AGL. The average ground resolution is 9.74 mm per pixelAgisoft Metashape Professional (build 2.1.2) was used to process 5,425 photographs into a single orthomosaic and DSM. All raster products have been shifted by 0.67m west and 1.0 m north to match the ITRF2000 coordinates listed for survey mark NMS54 in the AAD survey control databasehttps://transfer.data.aad.gov.au/aadc-applications/survey_control/AUSLIG_control_29Jul02/NatMap_stn_summaries_2/040142-00.jpg The Digital Surface Model is represented in two formats – an RGB (3 channel) representation for simplified viewing of terrain, and as a single channel (greyscale) file representing elevation. The single channel DSM has been corrected by subtracting 29.03 from the height value (originally in height above ellipsoid) to align the DSM with the orthometric height recorded for the survey mark (51.97m). The value of 29.03 was obtained from a nearby point on the boulder, to avoid the height anomaly associated with the mast.