Guest Column: Drone Dos and Don’ts
In the months since the FAA’s new commercial drone regulations came out, more and more surveyors are discovering how much value a drone can create in their businesses. A drone is a powerful tool for a surveyor. Surveyors are using drones to efficiently collect aerial maps on every job and create topographic maps more efficiently than ever before. It would be difficult to overstate the opportunity that drone technology presents. However, a drone is still just one tool in a surveyor’s toolbox; it is the right tool for some jobs and the wrong tool for others. Using a drone profitably requires understanding what a drone can do well and what it can’t, and thus what types of tasks a drone is well- or ill-suited for.
What a Drone Does Well
Creating Planning and Topographic Maps
The process of mapping by drone consists of the drone collecting overlapping aerial imagery and then using photogrammetry software to stitch it into an orthophoto and digital surface model. Most affordable survey drones are capable of producing maps accurate to 0.1 foot. This means that drone-made maps are good enough for creating topographic and planning maps.
Taking Photos and Creating a Record
As a flying camera, a drone is capable of efficiently taking a huge number of photos from a perspective that was previously unfeasible for most jobs. This means that it is now easy to collect a complete aerial record of any job or site, with minimal effort and cost. This also means that features of a jobsite that previously went unrecorded can now be easily mapped and measured, such as the tops of buildings, or features that were inaccessible because of terrain.
Flying in a Standard Pattern and Clear Airspace
A drone is very effective at completing simple, and boring, grid-pattern work. Rather than a surveyor having to spend hours walking a large grid, a drone can fly overhead and complete a tighter grid significantly faster. A drone effectively eliminates the tradeoff between linework resolution and the time a surveyor spends at a site. As long as the site is in standard airspace, the flight can be easily completed using the drone’s autopilot, meaning the surveyor needs only to set ground control before the flight and then monitor the drone as it flies.
Flying Over Hazards
The risks surveyors regularly face are irrelevant to a drone. Active roadways, working construction sites and perilous terrain are all easily avoided by a drone. The surveyor can position himself in a safe location and let the drone fly high above any hazard.
Covering Large Amounts of Land
Many entry-level commercial drones can cover up to 100 acres on one battery, and even more after an easy battery swap. The ability to fly over obstacles means there are few limiting factors other than battery life to covering more acreage by drone. Many higher-end drones can even cover a couple thousand acres in one flight, with only legal restrictions preventing this sort of use right now.
What a Drone Does Poorly
Extremely High Accuracy
Currently affordable drone technology cannot reliably produce maps to the 0.01-foot accuracy required for many engineering design projects. This means that drones are best for projects where extremely high accuracy is not required, such as topographic mapping, ALTA surveys or creating an orthophoto to back drawings.
Seeing Through Ground Cover
On a standard survey job, an autopilot-enabled drone will only capture imagery from straight above and at very slight oblique angles. While the drone does take photos with enough overlap to be able to model the terrain three-dimensionally, it is not enough to reliably see beneath overhanging features such as foliage or eaves. This means that a drone will not help a surveyor map the exact footprint of a building, nor the circumference of a tree trunk where it enters the ground.
While automated obstacle avoidance is rapidly improving, it is not yet capable enough to be relied on. Flying between trees, through buildings, around powerlines or even below bridges requires a very skilled pilot. If a site has a feature or obstacle that cannot be flown over, then it is not a safe job for a drone today.
Covering Massive Areas of Land
Drone technology can reliably cover plots of land even up to several thousand acres. However, above about 10,000 acres, drones will be less efficient than manned aircraft for the immediate future.
“Knowing” the Land
High-resolution imagery and 3D models cannot replace what an experienced surveyor is likely to learn by walking the land. Small signals, such as where ground is wet or a small trickle of water is moving, will tell an experienced surveyor what is happening on or beneath the land, and is unlikely to be recognized in drone maps.
The Wrong Jobs For a Drone
The limitations of drone technology mean there are specific types of jobs that drones will not be the right tool for in the near future. Drones are not well suited for jobs with a significant amount of ground cover. For example, when trying to create a topographic map of a heavily forested area, a drone will only capture the tops of the trees, not the ground below. Similarly, a drone will not work well when trying to map areas that have dense buildings, since the drone will not be able to reliably see the footprints of the buildings, particularly if they are close together.
A drone is also not going to be the best tool for a jobsite that is highly complex or irregular. For example, if a site has been built and rebuilt on a number of times, it may have small detail features that a surveyor is most likely to see by walking the land, and might be missed by drone. Small sections of underground pipes poking through the ground, or patterns in the dirt that show how water has moved, are clues that a surveyor can use to help build a complete and accurate map of land, and that would likely go unnoticed in a drone map.
Projects that require extremely high levels of accuracy, such as construction engineering design, cannot currently be done with drones only. The error level in current drone mapping is reliably limited to 0.1 feet in most circumstances, so using traditional high-accuracy methods are still best. Some technologies to produce higher accuracy, such as aerial LiDAR, are being developed but are not yet commercially viable.
Any site that is likely to have conflicted or complicated airspace is not a good place for a drone. If there are features such as very tall trees or high power lines, or the likelihood of unexpected low-flying aircraft like emergency vehicles or crop-dusters, then a drone is not a viable tool for the job. As obstacle avoidance and airspace-management technology improves, these types of jobs will become more viable.
The Right Jobs For a Drone
Despite the limitations, the capability of drone technology means there are a lot of jobs that drones can do very well today. A topographic or planning-stage mapping job for a site where the ground is easily visible from the sky is an ideal job for a drone. Mapping a site that is predominantly hardscape, dirt, or low ground cover by drone will be easy, efficient, and reliably produce excellent results. Completing those jobs by drone will take substantially less time than by conventional survey methods. On a standard 10-acre site, setting ground control points, operating the drone and completing post-processing usually takes one surveyor a total of six hours, rather than the full 16 hours it would take for a two-man crew. While learning how to operate a drone reliably does require training and operational know-how, good mission planning and autopilot software makes operating the drone simple.
Drones can also help surveyors expand their businesses. The 3D modeling capabilities of drones mean that it is easy to calculate volumes from drone maps. This means that a surveyor already working on a construction site can easily measure stockpiles or cut and fill volumes, providing these as additional services to the construction client. Surveyors can also use this volume-calculation capability to provide stockpile-measuring services to quarries. Additionally, the 3D modeling capabilities make measuring grades simple, meaning that a surveyor can provide daily grade measurements on construction sites or at mines. While working a construction site, a surveyor can also offer their client a construction monitoring service, via efficient updates of construction progress through daily aerial orthophotos and 3D models of the site.
Over the Horizon: The Next Era of Drone Capabilities
All of the capabilities discussed so far are feasible today, via affordable drone technology. However, as the drone industry continues to develop, there are a number of additional capabilities that are likely to become viable in the next few years.
Many surveyors are eager to start using drone-mounted LiDAR. Today, drone LiDAR is too expensive to be viable for most surveyors, with single systems costing as much as $500,000. However, the technology is advancing rapidly. When mature enough to be affordable for surveyors, LiDAR will provide significant benefits. The ability of LiDAR to shoot through foliage will eliminate ground cover as a limitation to surveying by drone, meaning surveyors will be able to reliably map completely unimproved and forested land.
Computer vision and smart obstacle avoidance technology are also rapidly improving. The coming years should present the first feasible drones that can autopilot around trees, buildings, power lines and even other aircraft. Additionally, it is likely that indoor-autopilot drones will start to become viable, allowing surveyors to use drones to map the insides of buildings or construction sites.
Finally, coming years should see the mapping accuracy of drones continue to improve. As camera, autopilot and data processing technology improves, it is realistic to expect that drones capable of design-grade accuracy will start becoming feasible for surveyors to own and operate.
To Succeed With Drone Surveying, Start Easy
Owning and operating a drone profitably and reliably requires more than just knowing what it can do. Selecting and integrating the right drone with the right mission planning, autopilot, operations, training and data processing is essential, as is making sure the operation is fully legal. This article lays out several capabilities and types of jobs that a drone can complete, but starting a drone program that can reliably accomplish these jobs can be complicated.
In Aerotas’ experience, the surveyors who are most successful at building profitable and efficient drone programs are those that start simply. Running an effective drone program requires becoming proficient with several different components, so the best approach is to start with the easiest approach that will prove viability and then grow with proficiency. Once a surveyor has successfully proven out the ability to generate valuable mapping deliverables by drone, then he is ideally positioned to leverage drones to grow his business in countless ways.
Drone technology is already providing value to the surveying industry, and the technology is only going to improve in the future. However, it is important to understand that drones cannot do everything for a surveyor; they will not replace a land surveyor on the ground any time soon. Though a drone can provide a huge amount of value for many surveyors, it is ultimately just one tool in a surveyor’s toolbox. In order to use a drone effectively, it is crucial to know which jobs it is the right tool for.