Does Your UAV Survey Program Measure Up?
In our work with surveyors around the country, we see that there is a huge diversity in how various surveyors use drones. More important is the huge diversity in how much the surveyors benefit from their drone programs. With such new technology, it can be hard for any one surveyor to know whether their drone program is benefiting them as much as it could be. As we discussed in our last column, making sure that a drone is providing as much benefit as possible is crucial as surveyors nationwide face the critical need to do more work faster to keep up with demand.
We have validated exactly what a well-implemented drone program should be providing using a coast-to-coast base of surveyors and having conducted nearly 400 hours of field testing and training. That finding: final line-work with 0.1 ft. or better accuracy in 60-90 percent less field time and no more office time than before, using existing staff, causing no extra risk, and costing less than $10,000. Does that sound like a stretch? Let’s look at each benefit in turn.
Your program should cost less than $10,000
Including the drone, training, insurance, and all the support equipment you need, an entire drone program should cost no more than $10,000. An inexpensive and non-specialized drone (e.g., small multi-rotor with a 20 megapixel camera) is good enough for producing industry-best accuracy.
We regularly talk to surveyors who spent 20 to 30 times more than the small multi-rotors we set our clients up with, and produce no better survey results. Unfortunately, more expensive equipment is also usually more complex. Given that the main benefit of a drone is time-savings, the focus when shopping for a drone should be on what is most simple and reliable for field crews, rather than what has the most impressive tech specs.
More advanced drone technologies are not yet good investments. RTK and PPK GNSS integrations on drones are often unreliable, complex to use and process, very expensive, with the only benefit being reducing (but not eliminating) the amount of ground control targets needed. Laser-scanners for drones are also extremely expensive and complex, and currently deliver far lower accuracy than drone photogrammetry. Fixed-wing drones are similarly expensive and more complex to use (as well as being more sensitive to weather and prone to damage), and do not provide any real-world benefit due to line-of-sight regulations.
Your drone should get you to final 3D line-work
The right drone, software, and workflow enables surveyors to produce final 3D line-work on every project. A surprising number of surveyors are satisfied if their drone program gets them just an orthophoto, which they use as client-pleasers or to draw 2D planimetrics. Other surveyors produce full 3D models, often as point-clouds, but don’t have an effective way to create their line-work from it. They are happy to show the 3D model to clients or use it as a stand-in for field photos to identify objects.
Surveyors in both of these situations are not benefitting from the drone as much as they could be, in time or money. The right drone workflow makes it easy for a surveyor to produce complete final line-work, including a TIN surface with breaklines, contours, and features.
Your drone should reduce field time by 60-90 percent
An effective drone program should provide massive time-savings in the field, even on complex projects. After setting ground control targets, the field operation for a drone survey should require only about five minutes of set-up. More importantly, there should never be a need to revisit a job to redo a drone flight. If setup takes more than five minutes or revisits/re-flies ever happen, this is usually because of insufficient training or an ineffective flight checklist.
It is important to understand that a drone is just one tool in a surveyor’s toolbox. The drone will almost always be part of a mixed workflow, with parts of a project still collected with ground equipment. In these cases, the drone still provides time savings, even if only on portions of a project. And with the right post-processing workflow, it is straightforward to merge together data collected by drone with that collected on the ground.
Your drone should cost you no extra office-time
Getting to final line-work from drone data should take a CAD tech the same amount of time as for a job using standard GPS or total station equipment. This includes getting from raw photos to a 3D model, then to final client-ready line-work.
If in-office staff are spending significantly more time to produce final line-work, the problem is the workflow. Trying to pull a 3D model directly into CAD software and complete the line-work there is rarely the most efficient solution due to limitations in CAD software for managing these types of files. Similarly, trying to create line-work directly from a point-cloud is always extremely inefficient. With the right software and workflow, doing projects by drone should require no extra office staff time or resources.
Your drone should get you accuracy better than 0.1 ft.
An effective drone program reliably produces surveys with less than 0.1 ft. tested vertical error (and substantially better in horizontal). Many surveyors simply do a few easy spot-checks and, if none of them seem too far off, they are satisfied. Unfortunately this can result in misleading and inconsistent results, and does not provide confidence in the actual total error. Fortunately, ASPRS Positional Accuracy Standards provide a straightforward methodology for completing a verifiable accuracy test of the total “all-in” error of a drone survey. This approach eliminates any bias or inconsistency in how the error is measured.
When measuring this root-mean-square error, the results should reliably be, at worst, 0.1 ft. vertical. If a final survey comes out with worse accuracy, the issue is usually a combination of field operation (e.g., ground control target layout), drone setup (e.g., camera settings, autopilot settings, flight planning), and/or the data processing operation (e.g., insufficient QA/QC procedures). While our system has been independently tested to 0.05 ft. vertical accuracy on some projects, we find that across a broad diversity of projects, 0.1 ft. maximum vertical error is currently industry-best.
Your drone program should require no special staffing
By using drone equipment that is simple and reliable to use, there is no need to hire a special “drone pilot.” Any staff that are qualified and trusted to operate a company truck can be drone operators. With the right equipment, training, support, and flight checklist, even the most non-technical field surveyor can become an effective drone operator. The drone is simply another tool they pull out of the truck to use. [editor’s note: “Qualified,” in the case of commercial use of a drone, should include appropriate FAA unmanned aircraft pilot certification.]
Your drone program should cause no risk
Using a drone in your survey business should not require that you accept more risk. There should be practically zero chance that field crews are unable to complete a job due to equipment issues, thus costing the business money. There should be no liability risk to the company. Most importantly, no person on-site should be put in any more harm’s way due to drone operations. It is essential that every drone survey program emphasize reliable equipment, a failsafe checklist, high-quality drone-specific insurance, and – most importantly – professional training. Used well, a drone program should in fact reduce risk by taking field surveyors out of dangerous roadways and other unsafe environments.
Make sure your drone program is helping your business
In this critical moment in the survey industry, surveyors need to be shifting how they think about their businesses. With construction and development up in nearly all parts of the country, and the nationwide shortage of hireable surveyors, it is more important than ever that surveyors make sure they are squeezing every bit of value out of the tools they use. For surveyors, a drone can be an incredibly valuable time-saving tool, enabling them to do more projects faster and more profitably, without needing to hire more staff. Now is the time to make sure that your drone program is getting you everything it could be – before the huge 2018 construction season begins.