Is Your Drone Data Survey-Grade?
In October 2017, the American Society for Photogrammetry and Remote Sensing (ASPRS) offered for the first time the final test for becoming a Certified Mapping Scientist-UAS. As the preeminent standards-setting and certifying organization for photogrammetry since 1934, the ASPRS has been at the forefront of determining how drones can be used to produce survey-grade-accuracy data. As founder and CEO of Aerotas, I sat for the test and was awarded ASPRS Certified Mapping Scientist - UAS certificate #002.
Many surveyors and engineers are still very skeptical of drone data. That’s understandable, considering how many surveyors I have talked to who were burned by getting inaccurate data on a drone survey project. Even more unfortunate is seeing the drone pilots out there claiming to have the skills to provide survey or mapping services without having the know-how to back it up. Sometimes, it’s just a matter of people getting ahead of themselves. I run into many drone operators who are excellent pilots with impeccable safety records, but that simply isn’t the same thing as being a photogrammetric scientist who can accurately collect and process survey-grade data.
It takes a lot of skill to get survey-grade accuracy using a drone. There are dozens of small sources of error that can impact accuracy, so standard operating procedures are necessary for collecting data in the field consistently, repeatedly and accurately.
However, ensuring accuracy also requires using ASPRS standards for measuring and verifying the accuracy of the final data. That’s one reason why I wanted to be one of the first people to get certified when ASPRS launched the UAS certification last year.
The certification covers a much broader set of topics than many would expect. It requires deep knowledge of both field and office work, from project setup and aerial ground control target layout, through data processing, to post-processing accuracy measurement and validation. The test requires an understanding of everything from how drones work, to the basics of photogrammetry, all the way down to the fundamental physics and math that supports it. I had to draw on my experience from every part of my professional career to be able to pass it.
The expertise this certification represents is essential for our clients to know they can trust the data we produce. The ASPRS certification is an even bigger deal for the surveying industry as a whole, though.
Going through the process of achieving this certification requires becoming extremely proficient with more than just drone photogrammetry. The exposure to a much broader set of photogrammetry, remote sensing, LiDAR, and even radar technology has helped me understand how aerial surveying can best be done, regardless of the technology and how it evolves.
The ASPRS certification requires the academic rigor that surveyors and engineers need to actually trust drone photogrammetry data. The members of the ASPRS put decades of research and experience together in order to be able to prove how photogrammetric data can be validated and trusted.
What’s also great is that the ASRPS standards are technologically agnostic. Whether data is captured with a camera on a stick, a drone, an aircraft, or even a satellite, those standards apply and an ASPRS certified professional will know how to mitigate error and validate accuracy. After all, the customer doesn’t care whether there was a person in the cockpit or not; they care if their survey was accurate. This has allowed the ASPRS to smoothly make the transition from manned-aircraft to drone-based photogrammetry.
The ASPRS has an eye on the future as well, since these same standards will apply to validating the accuracy of drone-based LiDAR data when it becomes viable for more surveyors to use.
The industry will ultimately get to a point where involving an ASPRS certified mapping scientist or technologist is a required part of any land surveying or civil engineering job that involves drone data. Anyone can say they know how to do aerial mapping, but someone with an ASPRS certification can actually prove it. Just like no one would see a doctor that isn’t licensed to practice medicine, they wouldn’t (or shouldn’t) use a photogrammetrist who does not have an ASPRS certification.
The Why Behind the Learning
Being able to prove an understanding of the science and practice behind drone surveying will likely soon become a requirement of most firms, and the ASPRS certification will be the best way for someone to prove it.
Unfortunately, we have seen first-hand why certification should be required. We have had to step in after an uncertified drone operator has produced bad data. Often, the issues begin in the field, with improper mission planning and improper use of aerial ground control targets.
We have seen “maps” produced with just a single flight-line of oblique photos and two or three ground control points on a project where the client expects an accurate topographic survey. As one might expect, the final data did not pass any of our accuracy tests or QA/QC checks and it had to be thrown out. In circumstances like this, the only solution is to re-fly the project with correct methodology and re-process the data.
However, often the main problems are in how the data is processed and the accuracy is verified. We have seen pilots collect data properly, but not have the deep understanding of photogrammetry required to preempt the many subtle sources of error.
One notable example came from a linear mission project that was flown over a 2,000-foot stretch of road. The surveyor set five aerial ground control targets in a straight line down the center of the road. In processing the data, all the automated checks that the photogrammetry software produces appeared fine, so the surveyor delivered the data.
What they did not catch was that, when ground control is in a direct line, the resulting model can twist around the line and lead to extreme inaccuracies – which the software’s internal checks are incapable of detecting. Catching this, and knowing how to prevent it in the future, takes the expertise that the ASPRS certification confers.
Surveyors are ultimately responsible for ensuring that the surveys they deliver are accurate to the specifications of the project and protect the public welfare. To do that, they need to have confidence that the data they are working with was collected and processed correctly. The only way to have this confidence is by knowing that at every step along the way, the personnel involved can prove their proficiency. When it comes to photogrammetric processing of drone data, the ASPRS certification is the best way to prove that.