Photogrammetry

Last year I tried something new with my UAS. Data mapping and 3D models. I used a software called Drone Deploy. It was amazing what can be done. However, I was skeptical about the accuracy. I was given a great opportunity to test it out.

A local business had a pile of sand that had already been surveyed (by ground crews) and a volume calculation was figured out.

Ground Survey

I wanted to compare with what I could figure out with this photogrammetry software. So, I flew the same pile. I took around 150 pictures and combining them with the GPS location and elevation of the UAS you can figure out heights of various points, thus creating a 3D model.

3D Map

With the 3D model, one can create an elevation map. This map shows the different elevations of each point created by photogrammety.

Elevation Map

Zooming in to the particular pile of sand in question, we can draw an area that is to be measured and calculate the volume.

Volume Calculation

In this project, we estimated the volume to be 131,883 cubic yards. It was higher than what the ground calculation estimated. So, we overlaid the ground survey over the aerial map and noticed the differences. 

Ground Survey overlay on Aerial Map

As you can see there are slight variations between the two maps. So, what does this mean? Well, I am pleased to announce that the numbers obtained from the aerial map were closest to the actual volume of the pile. This is the hard part, who really knows? Calculations can be made from scales on the loading belt, but those must be maintained for accuracy. In the end, this sand was loaded into rail cars and shipped out to customers. The pile was getting low, so I asked the client..."Well, who was closer?" It turns out that the aerial volume calculation was closer to the actual product shipped.

I don't get bragging rights, but it is good to know that the accuracy is there for volume calculation on a large scale. Ground surveying has been done for many, many years and their method is tried and true, there is no denying that, but I feel that there may be certain areas that were missed due to the height and shape of the pile. To send an employee up on the pile and put them at risk for injury, may not be worth the hassle.

Also, I was able to get flight and calculations done in less than 24 hours.

If anyone is interested in data mapping, contact us anytime.