Feature: Yearning to Fly
Professional Surveyor Magazine - July 2012
View Video clip here
UAV/UAS hit prime time.
By Gavin Schrock, PLS
“Can’t keep my eyes from the circling sky,
Tongue-tied and twisted,
Just an earthbound misfit, I.”
—David Gilmour, Pink Floyd
Trying to find a good vantage point from which to view and survey as much of a site as possible has likely had every field surveyor, at one time or another, wishing for a tripod a few feet taller—or a few hundred feet taller. I remember as a kid seeing the comic book hero Green Hornet’s sidekick Kato launch a little flying scanner from the trunk of the Black Beauty; only a decade later I was slogging through arctic tundra musing about how soon such a thing would be a standard part of a surveyors’ toolkit. Surveyors have long joked about a “flying total station” or at least something to fill a niche between conventional terrestrial surveying and full-blown aerial photogrammetry. Now it seems that tools of this kind are readily available.
The initials UAV (unmanned aerial vehicle) have implanted themselves firmly into the public lexicon with the maturation, wide adoption, and success of such technologies for military usage in recent conflicts. The idea is nothing new: Aerial observation has been around for centuries and various forms of aerial photography and photogrammetry for more than a century. Also not new is the notion of surveyors and mappers extending their reach into the sky: cameras on kites, remote-control (RC) aircraft, balloons, and more recently the advent of both home-built and sophisticated commercially produced “turn-key” UAV systems.
Shelving for the moment the wider discussions about drones, security, privacy, and other types of UAV, let’s look at the state of these turn-key systems for surveying by focusing on one that has gotten quite a bit of attention in surveying circles of late. Let’s also look at why we might consider using the initials UAS (Unmanned Aerial Systems) to describe these new tools—and seriously consider including them in surveyors’ tool kits.
UAV or UAS?
There are literally hundreds of commercially built and even do-it-yourself UAV kits and plans available, particularly in the lightweight categories. We see stories published weekly on innovative field applications of UAVs for surveying, mapping, mining, resource management, and precision agriculture; these range from the lightweight catapult or hand-launched RC-guided planes and helicopters to larger systems used by law enforcement and public safety. There are many choices to serve specific niches. I did not intend this to be a product review, but instead an examination of the subject by looking at an option that is now readily available—and there will certainly be more options to come. A standard step someone would take in evaluating a new tool is to solicit a user testimonial, i.e., to ask someone who bought one. In this case, I asked someone who didn’t just buy a UAV but bought an entire UAV company. More specifically a UAS company.
The news of Trimble’s acquisition of the Belgian UAS company Gatewing could have been viewed as just another acquisition—except that this is essentially the first time UAS has become part of the surveying product line of one of the major surveying and mapping systems providers. This fact gained a lot of attention in the general press and in industry-related publications. Anders Rhodin, general manager of the Trimble Survey business, spoke with a lot of excitement about the latest acquisition. “This is not a cool airplane,” he pointed out early in a recent interview with Professional Surveyor Magazine, adding, “This is a system designed specifically for surveying that just happens to fly.”
Rhodin has been in the business of surveying and development of surveying systems for more than 30 years. With a background in electronics engineering, he came to Trimble through the Spectra Precision acquisition; at Spectra Precision he had been directly involved in the development of the Geodimeter 140, 400, and 500 and was lead engineer on the 600. He explained that the process of adding UAS to the toolkit had been on his mind and those of many others in the company for quite a long time before conducting the formal evaluation and research process the past three years. “We concentrated on first evaluating the lightweight systems” he explained, meaning those lightweight systems (i.e., the 2kg Gatewing X100) that would first gain approval for wider use within the bounds of the civil aviation rules of various countries, with approval of the larger (55lb) systems on the near horizon.
He added, “We had to consider component weight and what types of cameras [and sensors] could be carried with such limitations.” One approach taken by companies in building their UAS was to build or acquire a plane, then to see what they could pack on it. The approach taken by Gatewing was to design a system specifically for surveying and then to design the vehicle to fully leverage that system.
Rhodin and Gatewing are adamant in pointing out that they characterize the X100 as a “camera integrated into a system” that is “carried by the aerial vehicle,” together forming a UAS. The standard camera is the Ricoh GR Digital IV that fits into a payload bay on the plane and can be swapped out with an infrared camera for applications like precision agriculture crop-health analyses. The control and command systems are also easily swapped out; in fact the “body” of the plane is designed to be semi-disposable. Components are easily and rapidly fitted into an inexpensive replacement body. (Bodies that may have been damaged or have reached the design limit of landings, typically around 50, must be replaced.) That’s not to say the “plane” part is unsophisticated (sure, there are some rigid foam parts in the design to meet weight and aerodynamics specifications); on the contrary, it’s not anything like a hobbyist’s radio-controlled craft. To perform as a stable camera platform, with limited flight duration, following well defined flight paths, and to compensate for wind drift, the in-flight control is not left up to the user.
You Do Not Fly the UAS
“There are things the [X100] does that could not be controlled by the user on the ground,” says Rhodin. Although the flight pattern is pre-determined in the flight planning software, you can add georegistered images and Keyhole Markup Language (KML) files to aid in planning. (KML is an open standard file format for geographic browsers that specifies features by latitude, longitude, and altitude.) The X100 launches from a catapult included in the kit, flies on rechargeable batteries for 30 to 45 minutes, and takes about 900 photos at a height (typical for most applications) of 150 meters above a subject area of about 1.5 km² along overlapping flight lines. The user only “flies” the craft to the extent that the user must ensure there are no obstructions along the flight path from the launch site, across the subject area, and to the landing site if it’s different from the launch site. Rhodin pointed out that you can take a GPS rover and simply log a different landing site if needed.
The inertial and GPS components of the UAS are simply for navigation purposes, to aid in correcting for cross winds, and to provide a rough initial position for each photo. Another feature contributing to the stability of the platform is the high speed of flight: as high as 160km/hr. While there is a live communications link (in the 2.5 GHz range), the UAS does not include direct line-of-sight flight control or point-of-view camera flight control; these would add unnecessary weight. So, those hours spent on the point-of-view flight simulators on your home game console may not contribute to your success with this UAS.
The flight is monitored via an included Trimble Yuma tablet; if communication is lost, the UAS will simply proceed to the landing site. Even if the UAS goes down out of the line of sight, the radio acts as a beacon with a range of around 30km for recovery operations. Plan well and, barring unforeseen circumstances (or perhaps an excitable raptor or amorous goose), all will go well. When the UAS reaches the landing site, it will go into a landing pattern and work its way down to a gentle landing. While the UAS can land on any flat and unobstructed surface, it does a belly landing (wheels or skids would have added too much weight), so a soft grassy surface is preferable to hard pavement or gravel.
Processing and Aerial Photogrammetry
The boom in softcopy photogrammetry in the past two decades gives the user many options for developing an end product. The data must first be processed through the orthomosaic software that comes with the full kit to export images for use in other software, or you can use Gatewing’s online cloud-processing service solutions.
While ground control is not necessary for some applications, and images are registered to each other by common pixel-recognition processing, the addition of ground control enables further registration steps for higher precisions—aerial triangulation, bundle block adjustment, etc., for orthophoto mosaic or stereo-based terrain model generation, and more. Depending on the types of applications, the list of innovative data management and processing options for this and other UAS will continue to grow.
Yes, one of the first questions that comes to mind when considering UAS is how they stack up against current methods and tools. “This does not replace aerial photogrammetry,” says Rhodin, citing the features of traditional aerial flights with manned aircraft: higher altitudes, more sophisticated cameras, higher resolutions, and improved resultant horizontal and vertical accuracies. The UAS flies optimally at 150 meters above the subject area. Assuming that the accuracy of a single pixel were to match that of properly coordinated ground targets, this could only be as good as 5cm, which is not accurate enough to directly compete with traditional aerial photogrammetry.
And while weight consideration may discount the inclusion of, say, airborne lidar payloads on this 2kg class of UAS, there are folks already working on the inclusion of other sensors. Even with the relatively low precisions, there are certain situations where a tool such as this can be of tremendous utility, especially with its rapid sortie turnaround and its ability to fly under the clouds (no waiting for a clear day). This type of UAS could fill some very specific niches in surveying and other industries, offering a cost-saving alternative to certain combinations of terrestrial methods.
Rules and Regulations
Rules, regulations, and laws for where, how, and who may use UAS vary all over the world. Some countries require a pilot’s license to fly one, and others have little or no restrictions. In the United States, as these UAS fall into essentially the same weight classification as hobbyists’ RC craft, there are few restrictions if you are flying for academia or just for fun. For commercial purposes, however, there are restrictions. While the recent FAA Modernization Act of February 2012 opens the door to commercial and other civilian/public safety uses of UAV/UAS, full clarification of the rules is not expected until May of 2014. The rules for the 55lb class of vehicle (carrying the potential for higher-precision instrumentation and sensor payloads) are scheduled for October of 2016.
In the interim, there are many places in the United States and other parts of the world where, if properly permitted in advance, these types of UAS can be used for a great many innovative applications. Early adopters of UAS for surveying and mapping have brought these little UAS into play for such uses as volume calculations for open-pit mines, crop health flights for precision farming, resource mapping (both conventional and infrared), site inspections, flood and landslide monitoring, and preliminary topographic surveys for site/route selection and preliminary engineering.
In the case of mining and farming applications, in less-densely populated areas with fewer airspace restrictions, users can perform multiple flights cheaply, frequently, with little overhead and minimal planning, which means more data, more frequently.
Is There Room in Our Toolboxes?
The cost of a full kit of a UAS of this type is comparable to that of a high-end imaging total station, with replacement bodies for this particular model about a tenth of that. A full kit for the Gatewing X100 comes in several hard cases, the control and communications units, camera, Yuma controller, launcher, orthomosaicing software, batteries, and accessories. Training takes three days and includes both office and live field days (I will be covering one of these “flight schools” in a subsequent article; see my video about it on the magazine’s website). It is very likely that other manufacturers will follow suit in the near future, and, as the FAA clarifies the rules and regulations, we may someday see a UAS in the toolkit of surveying firms both large and small.
The eager young techies I’ve talked to who develop UAV/UAS have set out not necessarily with the intention of replacing any current tools or methods, but rather to provide a few more tools that, where and when appropriately used, can save a lot of time and money. Certainly, the conversations about UAV/UAS will not be without controversy, but it would be hard to deny that the future of our industry will be unaffected by these innovative little birds and their larger cousins to come. The crew at Gatewing set out to design a UAS specifically to solve some specific surveying challenges. Anders Rhodin and his team at Trimble noted the strengths and limitations of the products, and, as Rhodin related, “This is not a complete surveying tool, [but rather] we see this as another tool in the surveyor’s toolbox.”
Gavin Schrock, PLS is a surveyor, technology writer, and operator of an RTN. He’s also on our editorial board.
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