Digital Elevation Models Revisited

The Model

Digital Elevation Models (DEM) are one of the outputs photogrammetry delivers. They are (almost) free, as long as you have GPS data (Latitude, longitude and depth) for known points then orientating and generating a view of the undulations of the scan is straightforward.

The SS Gwladmena was scanned back in August 2016. At the time was the largest & deepest subject tackled by Deep3D, requiring two dives and nearly a kilometre of swimming to capture the entire wreck. The results were worth the effort with the massive 4.2Gb ortho photo now available as an art print, and the 3D model allows the non-divers to get a feel of what its like to visit the wreck :-

The subject proved popular with the two models (the rather rushed version built on the boat, and a second more refined version derived later) being viewed around 2000 times.


Whilst it was not possible to gather GPS data in August, Kevin Heath of Sula Diving and Sandra Henry of UHI Archaeology Institute paid the Shetland Islands a visit with sidescan sonar recently and surveyed the wreck with grant support from the Nautical Archaeology Society and Historic Environment Scotland.

The resulting GPS points were added to the model, allowing us to get a simplified, clear view of how the wreck sits today.

DEM of SS Gwladmena. Image © Simon Brown.

The 3D model is great for interpretation, but the DEM simplifies the view and gives us a really clear understanding of the heights of the wreck. Which after being wire dragged after the First World War is not much. Irrespective of the clearance work, a really great dive.