[bowmessage]

Fascinating!

In the header image, the interesting gray-bar informational panel placed on the wreck caught my eye. I wonder what it's for?

I assume it's to calibrate scale and color for the underwater photography equipment, but would be interested to learn more from someone who knows for certain.

[kbutler]

Yes, looks like ground control points for photogrammetry. https://www.pix4d.com/blog/diving-into-underwater-photogramm...

[mikestew]

And why does it have a U. S. National Parks Service logo on it?

[throwup238]

It's a photogrammetry scale card made for the National Park Service, probably the Submerged Resources Center which often assists with this kind of stuff.

The NPS has a few different ones for paleontology, underwater archaeology, etc.