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Forest Surveys UAV Mapping Orthomosaic DSM DTM Drone Photogrammetry



3rd September 2019


To provide our client with imagery of a quarry on their land, along with a calculation of its volume.


Forest Surveys UAV Mapping Orthomosaic DSM DTM Drone Photogrammetry
Forest Surveys UAV Mapping Orthomosaic DSM DTM Drone Photogrammetry


The week of the 2nd September was an exceptionally busy one for us. With plans on the 4th, 5th and 6th to attend the Confor Woodland Show at Longleat House, and an exceptionally favourable forecast, we secured two lots of work in the region. On Tuesday the 3rd, we were in Somerset, capturing imagery of a vast, ancient quarry for our client.

This mission provided something of a unique challenge. Our client had informed us that the quarry was 300ft deep. According to CAA regulations, it is illegal to fly a UAV out over a decline in the landscape that would put the UAV at risk of being more than 400ft above the ground. Upon seeing the quarry, however, our team was a little sceptical of this estimation, and our pilot performed a manual flight from the quarry's lip down into its depths.

Monitoring the UAV's flight from above was an experience rarely encountered by our pilot, and he took additional safety precautions for doing so. Flying to the bottom of the quarry, the UAV controller's flight display confirmed the quarry depth as just under 200ft, meaning we were able to safely conduct the primary flight to capture the required imagery at the optimum altitude of 200ft for the mission. We supplemented this with a couple of lower altitude circular missions and a final manual flight into the depths of the quarry to acquire imagery from more 'oblique' perspectives (oblique meaning level, contrasted with the 'nadir', or top-down perspective).

We processed all 252 images into one high-res model, upon which we were able to conduct a volumetric measurement to determine the volume of the quarry, with an error value of <1%.


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