Deep3D were back in the wreck diving spiritual homeland of Scapa Flow last week, sleeping, eating and diving from the MV Valkyrie for 6 days of cold water fun. The majority of the wrecks of Scapa Flow date from the First World War and are very big subjects indeed. Previous experience teaches us that scanning large subjects can be exhausting and raises the risk of a bend. The Heart of Gold is intended to scan big subjects quickly, whilst maintaining quality. Since its first appearance the Heart of Gold has prompted a few questions from around the world. This post will fill in a few of the details.
What is the Heart of Gold?
Deep3D have developed the Heart of Gold to speed up the scanning process. Named after the probability drive powered spaceship featured in Douglas Adams’ The Hitchhikers Guide to the Galaxy, the whole idea of a scooter-lighting-rig-and-camera combo seemed improbable but it actually works.
The scooter is a Dive-Xtras Sierra (many thanks for the loan Lenny!) and the camera is a standard Subal housing. Lighting (not seen here) is an Orcalight Seawolf plus two Inon Z240 strobes. Mounting is via two Kent Tooling tank straps. The mount is homemade and comprises of sections of extruded aluminium sections, stainless steel fixings – basically anything I had to hand in the garage – plus some closed cell foam to get the rig as close to neutrally buoyant and balanced as possible.
Deploying and Driving
For small targets (more news on a recent small target coming soon) the scooter is not required and actually becomes a liability for things small enough to swim around and scan. But the Heart of Gold really does come into its own when the subject is beyond a comfortable swim. With something this big, jumping off the boat is not ideal, but being lowered down on the lift makes for a very comfortable entry. In the water and once on the target the lighting needs to be sorted, camera fired up and a few test shots taken to make sure the images are going to deliver the results. All of this takes a few minutes, but once set should be good for the entire dive.
The speed of scanning is highly variable, but typically will depend on:-
- How many frames can my camera shoot per second?
- How much overlap do I think I need?
- How bad/good is the visibility?
In Scapa last week the visibility was not great, but workable. However, care needs to be taken as the wrecks are highly irregular shapes. In low light on three occasions the Heart of Gold nearly ran into the aft gun turrets of SMS Coln. Not only do you need eyes looking ahead, but looking down to check the subject-to-camera distance is remaining constant.
Running a scanning scooter generates masses of images. My DSLR shoots RAW files and are 24Mb per frame and on a typical 60~70 min dive between 2000 & 3000 frames are shot. All need managing, so post dive they are imported into Lightroom for the all-important application and management of meta data. This step is easy to overlook, but when adding keywords and data to the images becomes priceless later.
With every image aligning, the 3D model looks great:
The Heart of Gold has its limitations, needs careful handling to get the best from it and can generate masses of junk data in no time if you get things wrong. But it does work and the results can be stunning. This orthophoto of the UB 116 is derived from 1602 separate images shot on a single dive: