The SS Yongala sank in 1911 during a cyclone near Cape Bowling Green in the central Great Barrier Reef. The wreck is about 100 m long lying on a flat seafloor in 26 m of water. The Yongala is one of the world’s top dive destinations as the wreck provides a complex habitat for prolific marine life.
Agisoft PhotoScan software to create an orthmosaic of the complete wreck. Julia Sumerling, a renowned underwater photographer, captured the photos during May 2015.We have been experimenting with underwater photogrammetry over the wreck, stitching together multiple overlapping photos using
Photogrammetry, or Structure from motion, is a range imaging technique for estimating 3D structures from 2D image sequences. The PhotoScan software first aligns the photos with sparse matching points, then creates a dense point cloud from the aligned photos.
Ground control points from multibeam sonar were used to map prominent points on the wreck into their correct geographic postition. A mesh was then created over the dense point cloud, leading to a digital elevation model with 1 cm resolution and an orthmosaic with 5 mm resolution.
Outputs also included a Wavefront obj file of the mesh and texture, and brought into Blender 3D computer graphics software for generating a 3D model of the wreck. The Blend4Web add-on in Blender was used to export a WebGL html file of the wreck for viewing the wreck in 3D through a browser.
A 5 cm resolution Google Earth kmz file of the wreck and WebGL html file can be downloaded below.