Photogrammetry Workshop Results

Background

I held my first photogrammetry class between Friday, Jan 20th through Sunday, Jan 22nd.

This the first time I held the workshop and the results were very good given the conditions we had for the dive day on Saturday, Jan 21st. After a day of lecture and building a model on land, we dove the Yukon and the Ruby on Saturday for the student to build practice models.

Models / Results

Land Based Photography Practice Model

The first exercise in the class is to take pictures of an object on land and build a model from that.

The student picked a fire hydrant and took the pictures and we built a model. I showed him some extra tips around trimming excess areas, reducing the photo overlays, etc. Here is a link to his model on Sketchfab:

Underwater Practice Models

We have had absolutely horrible dive conditions along the coast of California since the end of December.

When the visibility is low, it makes photogrammetry harder for a couple reasons: (1) You need to get closer to the target object which means that you need more photos to cover a given area and (2) It is harder to track “where you are and where you have been” on the object.

To provide an idea of the visibility, when we got onto the Yukon, our target was the stern gun which was right below the tie-off. I pointed out the guns to the student and he looked at me with a “where is it?” look. I pointed to it a few times and gave a hand sign for a gun but he still couldn’t “see” it. I took him down to the barrels where it then became clear where we were. The visibility was literally 5 feet or so and it gets “worse” when using bright video lights because the diffract against particles in the water.

Here is a picture of the student on the Ruby E pilot house (and the visibility on the Ruby E was “better” than the Yukon):

Yukon Stern Guns

As mentioned, the first target was the stern guns on the Yukon. As opposed to the guns at the bow, these have “stunted” or cutoff/short barrels that point directly down. Anytime you try to build a model of something “pointy” it can cause a challenge. Below is a link to the model he built:

I noticed one of the access panels swinging wildly so I took a short video of it. The student was below me so the bubbles filter through the video but you can get an idea of what I mean.

I thought that this was “new” since I hadn’t noticed it before; however, the same panel is open on my earlier photographs and model. But, the panels above the one that is vertically hanging down are newly separated. Here are a couple photos from when I dove the wreck prior and also a screen capture of my model.

Be careful when diving wrecks — especially after recent big storms. You never know what has shaken loose and is just dangling and waiting to collapse.

Ruby E Pilot House

The Pilot House model came out really well given the bad visibility and conditions and that it was only the student’s second “in water” model attempt. He was starting to understand the process of moving around an object to get all the angles and mentioned that he had formed a mental map prior to the dive. We had also discussed the route and how he should cover the object.

Below is a link to his model of the Ruby E:

Summary / Conclusions

The goal of the class is NOT just to learn the photogrammetry software, Metashape. The goal is to learn the process and techniques of building underwater photogrammetry models. The software is definitely one component, but there is so much more in terms of lens selection, camera settings, etc. that go into a successful project. Based on the results, I’m confident that the student can continue to practice and build models on his own and that the material and methodology is appropriate for teaching additional students.

Below is a quote from the student about his experience and the results:

I have about 2 years of underwater photography experience. I felt the class was taught at the perfect level. Brett was great at focusing on what I needed to know now to successfully start making models. I’m really excited with what I was able to make after just one weekend of class!

Photogrammetry Workshop Student

I’m not sure if/when I will teach another class. If there is enough interest, I will possibly conduct a workshop in the summertime.