Photogrammetry reveals Ōkahu Bay kūtai beds in stunning detail

Ōkahu Bay Photogrammetry
Ōkahu Bay Photogrammetry

You could be forgiven for thinking that the kūtai / green-lipped mussels have been hard at work clearing the murky waters of Ōkahu Bay.  Unfortunately, we would need square kilometers of kūtai beds to get the water this clear!  These images were stitched together from lots of smaller, close-up photos to form a composite image using photogrammetry.

In this case, two of the kūtai beds – S1 (shell base) and M1 (mud / sediment base) have been photographed by a diver, swimming in a spiral around a fixed stake in the middle of each bed.   Visibility at the time was only around 30-40cm (the diver could not see his hand stretched out in front of him) but you wouldn’t believe it when you look at the results. The images took incredible diving as well as technical skills to create. We will use them to learn more about how to restore our degraded seafloor.

Can you spot where the diver left his compass in the S1 bed? How many kūtai eating 11-armed starfish can you find? Not many eh? That’s great news!

Photogrammetry: Seascape/New Zealand Geographic with support from LiveOcean Foundation

Visit the Ōkahu Bay project page