Intro/Background
I’m currently finishing up the chapter in the book on the B-36 wreck off Mission Beach. It is quite a story and has taken more time than most of the other chapters to get it just right. It took a lot of additional research, reading and re-reading accident reports and newspaper articles to get every detail right. Similar to a few other chapters, I also decided to return to the site to see if I could create enhanced photogrammetry models for the book (and for on-line reference).
I had mixed results. My goal was two models: (1) the three engines lined up at the main debris site at 255 feet deep and (2) a combined model of the engine & propeller that are about a mile away.
Dive 1 : Main Debris Site
I dove this wreck once before and it is always one of those wrecks that is a bit uneasy to dive alone. It is always dark and the silt-out factor is very high. Also, the windlass on the Marissa was inoperable so I knew I would need to send up a lift bag on the downline to help float it. Normally, this isn’t a problem, but when visibility is 5-10 feet and I’m trying to take photos and manage a full-frame camera with video lights, etc. it can be a bit much for one person.
The dive went well but I did kick up some of the fine silt which hampered visibility. Lora’s downline was perfectly on-target on one of the engines. I started to photograph that engine and then went to find the other engines. They aren’t more than 10-15 feet away but it was so dark that I couldn’t see any other engine so I started in one direction taking photos for the model. After a short while, I realized that they must be in the other direction so I headed back and then passed the initial engine and took photos of the other two. The last one was tough since I hand’t run a line and I couldn’t see my strobe on the downline but I had taken a compass heading. I “dove by braille” and found my way back and ended the dive.
The resulting model isn’t great and I’m not happy with it but I wanted to get it published in case anybody else wants to see it.
Sketchfab Model Below:
Dive 2 : Engine & Propeller
On my initial dive on this site with Drew, I was still early on in my photogrammetry learning and made a basic model of the engine. My goal on this dive was to make a model that had both the engine and the large 19 foot diameter propeller in the model to illustrated the relationship between the two. It was slightly shallower than the main debris field so I had a little more natural light, but it was still dark with limited visibility. The downline was at the prop (you can see the grappling hook in the model below) so I started taking photos there. Photographing props for a model can be hard because the are skinny and sharp angles in one direction.
I then left to find the engine which was at (or beyond) the edge of visibility (it is about 50 feet away). I saw a shadow and some fish and started to swim there, taking photos as I went (this is the only way to get both objects in the same model without markers and expensive versions of the software). I went slightly off-course as you can see in the model but found my way there. I took the photos of the engine and then more photos as I navigated back to the propeller.
This model came out pretty good. It took a bit of post-processing on the photos to get the colors right and to cut out the mis-placed video light which created a bright spot in the photos, but I’m pretty happy with it.
Screen capture of the model and some notations:
Screen capture of the large 19 foot diameter prop (note how well Lora & Chris placed the downline):
Link to the on-line model below:
