discussion / Sensors  / 19 January 2017

Photogrammetry: mapping caves and other environments


I need some advice on photogrammetry. Is there anyone here that has used these methods and would be willing to provide some pointers?

Specifically, I am aiming to create a 3D model of a bat cave (50 m deep, 10-20 m wide). Any guidance appreciated, on standard methods, equipment, and software.

Many thanks


Hey Ollie!

This strikes me as something quite similar to what some of the folks in the drones world are trying to do with mapping forests, except basically inverted. @Tomswinfield shared an overview of what he's been working on in this case study: 'Can UAVs be Used to Measure Forest Quality', which may be a place to start to see if there are any similarities in what you're thinking. @Tomswinfield @Felipe-Spina  and I had a fascinating discussion this very morning about this approach, so perhaps one of you could offer Ollie some pointers? 



Hi Ollie, 

I've only used UAVs to map forest canopies but the principal is the same:

- Multirotor UAV with a camera pointed towards the surface to be mapped (aim to keep the angle relatively constant)

- Create a flight map that enables you to collect equally space images with >60% overlap with adjacent images (in all directions); this can be achieved easily with Mission Planner, particularly if you have a constant flight speed and the camera is triggered by an intervalometer. You could alternatively set images to be taken at particular way points. 

- Use Structure From Motion software (e.g. Pix4D / Photoscan) to build your 3D model as a point cloud or render to a mesh. 

- Job done.

Any more questions, just ask. 


Thanks for that Tom!

As a broadly knowledgeable beginner, reading your instructions makes me wonder if it might not be valuable to have a step by step guide that is a little more detailed than that on getting started (and I'm by no means suggesting you need to write it!). @ollie.wearn  , as someone just getting started, and @Felipe-Spina , as someone a little bit futher along but still experimenting and learning, what do you think? Would a simple 'how to get started using your drone to map in 3D' (with a hopefully snappier name) sort of guide be a useful thing to develop for others coming after you? Or does this sort of resource already exist? 

I should say - anyone else with thoughts or suggestions on Ollie's original question or my follow up here, please do chime in as well!