Aerial 3D Photogrammetry without a drone or UAV.

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How on earth could we produce a 3D model, where drones are not allowed?

When researching a route to a training establishment for a recent QGIS training course, we were intrigued to see a ‘pin’ on Google Maps for a something called ‘Arthur’s Stone’, which appeared to be a small neolithic burial chamber, overlooking the ‘Golden Valley’ in Herefordshire.
We immediately wondered just how this would look as a 3D model!

Investigating the site further, it became clear that it is in the care of English heritage, and their website is quite clear that they won’t allow drone operations on any of their sites except in very specific circumstances.
As it was to be a quick visit, we wondered if it would be possible to take ‘aerial photos‘ with one of our cameras on top of our 12 meter ‘camera pole’
There was only one way to find out!

An image of the pin for 'Arthur's Stone' on Google Maps
The 'pin' for 'Arthur's Stone' on Google maps

It took just over an hour to drive there, the last couple of miles being on a single track road, with very few passing places. We found enough space for around 3 cars, but at least there was a gap to park!
After waiting for the half a dozen or so of the people already there to depart, and a group of walkers to pass through, a couple of photographs to set the scene.

Arthur's Stone, a neolitic burial chamber
Arthur's Stone burial chamber.
Photograph of Arthur's Stone neolitic burial chamber
Arthur's stone burial chamber

A total of 30 photos were taken around the circumference of the fence surrounding the site, utilising our Sony A6300 DSLR. Then it was attached to out camera pole, and the process repeated with the camera on the camera pole, raised to around 10 meters above ground. Some 15 photos were taken from various points around the surrounding fence.

Back at base later, the photographs were loaded into 3DF Zephyr, photogrammetry software, as a test of it’s capabilities.

A range of the photos imported into the software

Good matches were only found for 46 of the photos, so only these were used by the modelling process, after a short while, the following sparse and dense point clouds were displayed.

The sparse point cloud generated
The dense point cloud generated -in need of tidying up!

It was fairly straightforward to select the points that we required for the dense point cloud within the software, we eventually settled on using the ellipse tool , seeing that the site within the fence was somewhat circular, then inverting it and removing all the points outside of the ellipse. The resultant mesh appeared to be surprisingly good considering the relatively small amount of photographs used!

The finished mesh

To finally display the 3D model, the mesh was imported into meshlab, and a short video made. This demonstrated a full 360 rotation of the site, followed by a 90 degree rotation from ground level to display the model from above.

This shows that even when it’s not possible to use a drone, for whatever reason, it is still possible for us to deliver results, using the right tools for the job.

If you’d like to discuss any image, video or data that you require, be that ground based or aerial, mapping or modelling, please do feel free to contact us.

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