ALBERT

Description: Orthomosaics for this project were created using Structure-from-Motion (SfM) algorithms from drone-derived imagery. The resultant orthomosaics have 2 cm resolution and are georeferenced to the GDA94 MGA zone 54 coordinate system. Positional accuracy is subject to errors from the on-board GPS and estimated between 5-10 m. GeoTiff data is available and can be requested. Please email the author (jleon@usc.edu.au) and provide a brief paragraph as to the intended use of the data. Images were acquired with a DJI Mavic Pro drone (〈 2 kg) at 50 m altitude using DJI Ground Station Pro mission planner. The drone was operated as part of a GBRMPA accredit institution (University of Queenland). The following were considered to improve image quality over water: - The camera was tilted 10 degrees off nadir - 90% forward / 60% side overlap was used - Flights were undertaken only when wind was 〈 15 knots - Sun azimuth was kept away from the flight direction to reduce glint - Flights were mostly undertaken before midday to reduce glint, although this was not always possible. Similarly, timing low tide levels was not always possible. Images were processed using Agisoft Photoscan 1.4.3 software using the following steps/parameters: - Alignment: Highest accuracy - Resultant sparse point cloud was cleaned selectively and manually. - Build Dense cloud: High quality, Aggressive depth filtering - Calibrate colours: source data - model, no white balance correction - Build Texture: Generic mapping mode - Build DEM: source dense cloud, resolution - 0.02 m/pix, projection - GDA94 MGA zone 54 - Build Orthomosaic: Surface - DEM, resolution - 0.02 m, projection - GDA94 MGA zone 54