How a Colo. PD reconstructs the scene with UAVs
The “bread and butter” use for the technology is crime scene and accident scene reconstruction
By Becky Lewis
Tech Beat Magazine
Another big one out on the Interstate. Couple of tractor-trailers, a half-dozen cars. Every hour the road is closed to survey the scene costs the local economy thousands of dollars.
But today, the loss won’t be as great. Today, the highway will reopen in just about an hour. Today, investigators won’t have to take an excessive amount of time out of concern that they have missed a key photograph or measurements, because their “eye in the sky” is documenting the scene quickly, thoroughly and in far less time than they could on the ground.
When the sheriff’s office in Mesa County, Colo., became one of the first law enforcement agencies in the country to receive a Federal Aviation Administration (FAA) Certificate of Authorization (COA) to implement wide-area use of small unmanned aircraft (sUAS), UAS Program Director Ben Miller says he thought the aircraft would become primarily a search-and-rescue tool. (Mesa County is the fourth largest county in Colorado geographically, and has a population of 147,083.) Instead, it seems to be turning out that the “bread and butter” use for the technology is crime scene and accident scene reconstruction.
“We had the idea that we would be doing everything you see police helicopters do in the movies,” Miller says. “We quickly realized there are limitations because of size and weight, and we began to realize that the real key mission is not finding lost hikers and chasing bad guys, it’s day-to-day aerial survey capability.
“In Colorado, it costs the economy $35,000 an hour to close I-70. If an agency spends $25,000 to $30,000 for an sUAS, and it cuts the time the highway is closed from three hours to one, it’s paid for itself during the first mission,” he says.
Mesa County flies two sUAS, a two-pound Draganflyer X4-ES unmanned helicopter and a larger fixed-wing craft called the Falcon UAV. The sheriff’s office received its first experimental COA and began a pilot program with the Draganflyer in 2008, then received the expanded COA to fly almost anywhere in the county in 2009. The agency added use of the Falcon in 2012; both craft were donated by their respective manufacturers to the pilot project, although Mesa County pays for parts and service. Miller describes their aerial survey capability as similar to the process used by Google Earth or other public-sector products, but with a significantly greater accuracy. The sUAS fly at a specified height above the ground and take a series of extensively overlapping photographs, presently programmed manually, but with the potential for robotic control in the near future. Modeling software identifies “like” points from the pixels in the photos, and the overlap allows a triangulation algorithm to produce detailed 3D models proven to be accurate within 3 centimeters.
Mesa County received a donation of software that would normally cost $3,500 to obtain that accuracy, although Miller expects that in the future, sUAS manufacturers will bundle it in with their devices.
“It’s easy to believe in hardware, but although software provides a product, you don’t see the process it uses to create that product,” Miller says. “We were very skeptical at first about its accuracy, because typically software has bugs. With this, we haven’t seen any bugs. We feed it photos and it produces a model, and we feel comfortable taking its accuracy to the witness stand.”
And because the photographs remain on file, if an investigator wants to “revisit” the scene and take a different measurement later in the process, the crime scene remains always open. This provides another level of reassurance that it’s okay to release the actual physical scene.
“The time savings compared to doing it manually are tremendous,” Miller says. “Also, we’re not using modeling software that uses a template of, for example, a Ford truck, then extrapolates from there. You have a photograph that shows the actual vehicle involved in the incident, and everything in the surrounding area is there, every tree, every rock. The distances are accurate and everything is in its precise position. The increase in available data is significant.”
Miller makes that statement based on six years of experience with using sUAS, during which Mesa County has used the aircraft in various search-and-rescue and tactical missions, in addition to using them for crime scene reconstruction.
“We initially were thinking more about the ‘fun’ stuff,” he says. “Most agencies want to talk about using sUAS for tactical missions, but our opinion now is that what we originally thought was the most obvious use is really the least frequent mission. Aerial mapping is really going to turn out to be number one.”
For more information on Mesa County’s use of sUAS, contact Ben Miller at (970) 244-3955, or by email at email@example.com. For information on the National Institute of Justice Law Enforcement Aviation Technology Program, which identifies and evaluates the use of safe and lower cost aviation assets by smaller, predominately rural, law enforcement agencies across the United States, contact Program Manager Mike O’Shea at (202) 305-7954 or by email at firstname.lastname@example.org.