Landscape Photogrammetry

Following on from my previous drone/photogrammetry activities I decided to have another go but with a few improvements to the technique:

  • Using the 2.7K video rather than 1080p HD
  • Using more images – in the end this had little effect so I kept to roughly the same number as before to keep processing times manageable
  • Experimenting with the Alicevision Meshroom settings – I based my experiments on this blog post by Peter Falkingham but again I found that the default settings were actually fine so I stuck with those.

Quarry Face

This is is part of the Foel Fraith Limeworking complex on the Brecon Beacons, Wales which I’ve written about before [ 1, 2 ]. The quarry face is about 40m wide and the model was created using 150 images extracted from six passes along the face of the quarry at different heights ( right ).

I’ve tried in the past to create a model of this quarry face using my dSLR but I couldn’t get enough vantage points to be able to create a mesh without big gaps. This time it worked much better and only needed a little cleaning up around the edges.

Quarry Buildings

The next target was some ruined quarry buildings from another part of the complex. In this case I used the “Circle Quick Shot” option on the drone at four different heights ( right ). Ideally I would have liked to go lower but the terrain rose sharply at one point ( out of shot ) and the drone has no collision avoidance so I erred on the side of caution 🙂

Meshroom had no problems with reconstructing the scene but I felt that it lacked enough interest and detail so I didn’t upload it to Sketchfab. Below is one of the original images and a screenshot of the actual model.

The model has been created with no problems but to me it lacks detail. I’m not quite sure why this is but I’m probably pushing it even with the 2.7K video. It’s possible that I could tweak the Meshroom settings but that would probably increase the processing time. A jumble of very similar rocks is also probably not the easiest subject to model either!

Winding House

The third target was the remains of a winding house associated with a cable hauled tramway. Unfortunately this suffered from the same problem as the buildings above in that the model was created with no problems but it lacked enough detail to be of real interest.

Conclusion

They say practice makes perfect and I’m getting there slowly! Capturing the images now only takes about 10 minutes for each subject and I can be reasonably confident that I can successfully create a 3D model when I get home. The Alicevision Meshroom software seems to be pretty good and stable and the UI is an improvement over openMVG/openMVS.

The lack of detail on the two buildings is a little disappointing but it’s possible that just using the Circle Quick Shot is not the best approach here. Maybe I should also try some linear passes like the quarry face – that way I could get lower and closer to the object that I’m scanning. Other than the Quick Shots mode the Mavic Mini doesn’t have any options for automating the flight path so any different approach needs to be simple. My video gaming skills are nowhere near good enough to fly complex patterns manually!

One other avenue of investigation is that the drone doesn’t have to be in flight to take video. In effect I have a very nice hand held, gimbal stabilised camera which I can use to supplement any aerial shots, for example for close ups or where flying could be tricky. There are plenty more ideas to try.

1 thought on “Landscape Photogrammetry

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