By 2021 more than 440,000 commercial drones are expected to fill the nation’s skies, 10 times the number out there today. For many applications, the technology captures equally accurate data faster and less expensively than traditional surveying methods, but one negative news report could derail a public agency’s drone program. Before yours begins investigating applications, there’s much to consider.
Addressing the public’s privacy and safety concerns is paramount. Your agency must learn the rules of the airways, which means related federal, state, and local legislation; and acquire the expertise to operate drone systems, which often include software. If you outsource flights, you still must understand how to manage the technology safely and without incident.
The Federal Aviation Administration (FAA) didn’t officially address non-military unmanned aircraft until five years ago. The Federal Modernization and Reform Act of 2012 established the Section 333 exemption, a case-by-case method by which public agencies can obtain a certificate of authorization (COA) to operate drones in the national airspace system (NAS). In August 2016, the agency removed a major obstacle to widespread adoption by adding Part 107 to Section 333. Instead of getting a traditional pilot's license, people who operate drones for commercial purposes must score at least 70% on a remote-pilot certification test. Free classes are available through FAA.org and test centers are located throughout the country. Roughly 90% of students pass on the first attempt.
You've got two types of drones to choose from.
Here's how to decide which one's right for your needs.
- Quadcopter Helicopter lifted and propelled by four rotors
- Applications Inspecting hard-to-reach assets (bridges, dams, water towers, aboveground pipelines) and confined spaces (pump stations, culverts); volumetric analysis (asphalt and concrete for road work, earthmoving, etc.)
- Flight time per battery charge 25 minutes
- Distance per battery charge 150 acres to 250 acres
- Speed About 25 mph
- Pros Easy to use, very accurate (within 1 centimeter), images extremely clear, needs about 1 foot of space to take off and land
- Cons Slower
- Fixed Wing Aircraft with wings instead of rotors
- Applications Anytime range is more important than accuracy (landslides, flooding, disaster relief, search missions to find signs of people in large areas)
- Flight time per battery charge 40 minutes
- Distance per battery charge 1000 acres to 2000 acres
- Speed About 40 mph
- Pros Faster, longer battery life and range per flight
- Cons Less accurate (within 6 inches), images/measurements can blur when unit turns, longer runway-style takeoff and landing
Cameras and sensors can be mounted to each type. However, their weight compromises battery life and range. Often, users can extract multiple data types from a single flight via post-processing analytics. This eliminates doing separate flights to gather data from different measurement tools. Most public works agencies use a quadcopter because they’re more concerned about accuracy than range. Source: Identified Technologies
Waivers are still required to fly at night, within five miles of an airport, over people who aren’t part of the flight operation (including operator and observer), or beyond line of sight, but government agencies now have a choice: They can apply for a COA or follow the rules developed for business, which is Part 107.
Click here to learn what waivers are required to operate around airports and why.
“We anticipate doing both,” says Cassandra Issacson, aviation director for Minnesota DOT (MnDOT), which plans to buy two multirotor drones this year. In addition to bridge inspections, the agency’s compared how drone photogrammetry compares to vehicle-based LiDAR and used drone images to update the public on projects. “For many missions, Part 107 is sufficient. But if any part of the mission doesn’t easily comply, put on the brakes and consider if you need a COA or special waiver. Whatever the technology, the foundation is the same: The pilot is responsible for mission safety. It’s very easy to get in trouble, especially if you don’t have a background in aviation. It’s not enough to look on a website.”
Drone developers are exploring the viability of technologies driving (no pun intended) autonomous vehicles. Regulations will evolve if collision-avoidance systems, geofencing, and autonomous operation minimize or eliminate public safety and security concerns. Earlier this year, FAA formed a committee to create standards for remotely identifying and tracking drones during operation. “This is one of law enforcement’s top concerns,” says FAA Administrator Michael Huerta. “We hope the recommendations we receive will pave the way for expanded operations over people and beyond line of sight.”
Until then, says Oregon DOT Geometronics Manager/Surveys Chief Joseph Thomas, “flying over traffic is an unknown and a pretty huge risk.”
The agency got a COA in 2005 and has used a Leica Geosystems Aibot X6 Hexacopter to survey gravel pits, landslides, and a highway project. It’s working with Oregon State University to measure the impact of drones on drivers; results are expected to be released in January 2018. “Until we see what that study shows, we’re not going to be in a big hurry to fly near traffic,” Thomas says.
Despite these caveats, public agencies are using drones to survey more safely and efficiently. In March 2016 the American Association State Highway Transportation Officials (AASHTO) found that 17 state DOTs had researched or were using drones.
Survey more safely
Safety was the reason for using a drone to map cracks in the walls of an iron ore mine over which MnDOT is building a new road and bridge, a project called the Highway 53 Relocation. Before buying land, the agency wanted to know if rock along the alignment’s non-bridge portions was stable enough to accommodate mining operations.
Because of the large area to be analyzed, drilling additional borings to recover and log rock core was cost-prohibitive. In addition, given their near-vertical nature, climbing down the 200-foot open pit mine walls was dangerous and would take hundreds of hours.
“The drone was safer and measured a much larger area of the nearby slopes in a few days,” says MnDOT Assistant Engineering Geologist Andrew Shinnefield. “With the increased data density from the photogrammetry, we had more confidence in the rock properties used to evaluate the slopes’ stability.”
His team hired Itasca Consulting Group (ICG) and Itasca Consulting Canada (ICCI) for the project. Based on mapping needs and photogrammetric principles, Itasca devised autonomous flight plans ahead of the fieldwork.
The firms then retained Picture Factory Inc. of Hudson, Wis., which has a Section 333 exemption to provide aerial imagery for film, video, television, and live broadcast and employs Part 107-certified pilots, to survey the walls. The company used its Cinecopter S1200 +, a modified DJI Spreading Wings S1000+ equipped with a Nikon D5300 digital single-lens reflex (DSLR) camera that captured 3,000 photos over 11,000 feet and a GoPro video camera that provided a live feed to the remote pilot and observer.
Itasca partnered with 3GSM to process images using ShapeMetrix3D, software developed specifically for rock mass characterization and volumetric measurements. Ultimately, more than 3,100 joints were mapped in 3D.
MnDOT’s aviation department provided safety procedures, but scheduling was challenging. Picture Factory had to receive a COA from FAA, and Picture Factory and Itasca had to find a mutually acceptable date that also had good weather.
About a year later, MnDOT Project Director Patrick Huston began using the images to walk the public through the project virtually at outreach events. “The images paint a more comprehensive picture with context,” says Huston. He uses drone photos at monthly update meetings and on the project’s website.
In-house drone operation
Having hired consultants to deploy drones over the last two years, MnDOT plans to buy two this year: one for Office of Land Management surveyors and one for bridge inspections.
Criteria for selection are safety, mapping requirements, and price. For the small-footprint areas the agency plans to assess, Assistant Surveying Director Peter Jenkins believes a multirotor drone best fits the agency’s needs and budget. The survey group’s drone must be capable of vertical photography (lens facing straight down) and autonomous operation via preprogrammed flight plan. The other drone must be able to look up at the underside of bridges, take video, hover, and alter perspective until the proper image is captured, operations that require human control using a joystick.
Including software, safety features, training, parts replacement program, and warranty, Land Management’s drone is expected to cost $30,000 to $50,000. However, ownership provides immediate access in an emergency, such as a landslide. Other applications include investigating illegal dumping at landfills and evaluating how much material in gravel pits is available for road construction, two tasks the agency could not afford to do before.
The survey group expects two employees to become Part 107-certified and use the drone two or three times a month. If demand expands, MnDOT would have to add staff or consider a drone service company for certain projects.
Results: photos vs. lasers
One reason the agency didn’t buy a drone sooner was data quality. “We were skeptical about accuracy because the platform is a bit unstable,” says Jenkins.
Photogrammetry uses photos to measure distance. LiDAR does the same thing by illuminating the target with a pulsed laser light and measuring the reflected pulses with a sensor. Last year, MnDOT compared the two by closing a trunk highway’s intersection for nine minutes while Jeff Walsh, owner of Peregrine Inc. in Chaska, Minn., assessed the asphalt via multirotor drone in a zero-dollar partnership. MnDOT had previously assessed the pavement via vehicle-based LiDAR, but the technology’s too heavy for drones (total drone weight cannot exceed 55 pounds).
“We were pleased with the results,” says Jenkins. “There weren’t large variances. We’ve seen so many advances in micro technology that have improved the accuracy of the data as well as software advances. We’re very comfortable using drones to supplement our normal work.”
Jenkins doesn’t see drone photogrammetry replacing vehicle-based LiDAR for longer stretches of road. Photogrammetry also can’t be used to survey softer, grassy areas, or under tree canopy.
He can, however, see a time when contractors fly drones over jobsites daily to determine how much material was removed or pavement placed and submit invoices weekly.
“As long as the contractor shows a drone is a more cost-effective way to complete work and the safety plan is agreeable to the public agency, I don’t know why a DOT wouldn’t consider it,” Jenkins says.