What’s the difference between scanning wrecks and caves? Part 1.

What’s the difference between scanning wrecks and caves? Part 1.

Similar, yet so different. Over the past few years, I have been involved in numerous underwater photogrammetry projects. These include my own projects and those where I served as a technical advisor. One thing I’ve learned is that they have surprisingly little in common.

I’ve decided to create a series of posts that cover the major differences, including:

  • The reasons we conduct the scanning survey
  • Hardware setups for wreck and mine scanning
  • Various methods of photo material acquisition
  • Different approaches to expedition planning
  • Ways to present the outcomes, including the optimal use of novel technologies like AR and VR

Today, let’s focus on the first point. Why do we even attempt to scan a specific object? A wreck, for instance? Wrecks are subject to natural degradation, so creating digital documentation is sensible when it comes to determining degradation rates and preserving cultural heritage. The actual reason we go there is simple - we know the wreck is there. We know it will degrade over time. 3D scanning techniques allow us to preserve it as it is today. It’s worth noting that the degradation can be due to both natural factors (corrosion, strong currents, etc.) and human activity. Theft, in other words. The SS Steuben, which took part in Operation Hannibal (the German evacuation from East Prussia in the face of the Red Army’s approach at the end of WW2), is a good, yet sad example. In pictures taken in 2004, we can see some beautiful artifacts like the steering wheel, compass, four telegraphs, and others. Today, they are all gone. We can only regret that at that time, performing a 3D scan was not yet possible. (Maybe it was, but only with specialized equipment that few could afford - nothing that would be available for enthusiasts). So, to summarize - when scanning a wreck, what we are doing is actually creating a snapshot of its current state.

A side note here - a similar approach can be applied to glacial caves that undergo radical changes in shape within just one year, making digital documentation crucial for understanding their processes.

Things are different when it comes to scanning mines or caves - both being extensive systems of underground corridors. With these kinds of endeavors, our motivation will be completely different. It’s safe to assume that these sites will not change or deteriorate drastically over time. This assumption holds true especially for caves, where changes in the shape of corridors occur over millions of years due to karst phenomena. When performing a scan, we should think mainly of cartography. A detailed 3D scan (a digital twin, in other words) can (after some digital processing) become a high-quality map. This was the case in two of my projects in Polish mines - Maria Concordia and Marie Agnes. Another thing to consider is the improvement of divers’ safety. It’s safe to assume that diving in an unknown place is a stress factor. Being in possession of a 3D scan of an overhead environment, we are free to create a fly-through animation that, when watched before the dive, can give a good understanding of what awaits us. This cartographical and educational approach also gives us plenty of opportunities to experiment with immersive technologies like AR and VR (which will be described in detail in one of the upcoming posts).

Whatever we decide to do with the scan and whatever our motivation for the scanning is, the first thing we need to think of is the hardware setup - differing drastically based on whether our object is a wreck or an overhead environment. You want to know the differences? Stay tuned for part 2!


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