Working without GCPs is a totally new chapter for earthworks, Wingtra’s senior product manager Julian Surber said when the company announced the new SURVEY61 payload. Well, the simple fact of the matter is that ground control points are one of the least efficient aspects of the entire process of utilizing a drone for surveying. It’s because of the fact that the time taken up simply setting up, measuring, and resetting the ground control points, which are required to be placed in a visually accessible area, could be hours before ever taking off into the sky. Naturally, when one considers an earthworks site, a highway, a landfill, or some type of construction, the issue with ground control points that are visually accessible becomes, in many ways, more than simply a function of efficiency; it becomes a safety issue, depending upon what type of earthworks, highway, landfill, or construction site one is speaking about.
The approach taken by Wingtra, however, is quite unique and one that, with a payload and an air vehicle, promises to change the paradigm entirely. The SURVEY61 payload, which will be utilized in conjunction with WingtraRAY VTOL Fixed Wing, is a PPK solution, which means that the image will be corrected while still in the air, rather than having to be corrected upon the ground with ground control points. The system will be able to obtain survey grade results down to 3 centimeters while capturing image data at less than 0.5 inch per pixel from 400 feet above ground. Naturally, while the earthworks, topography, and construction world is concerned with how fast a drone will be able to fly, the time required to get a job done, no matter how fast one is flying, remains, ultimately, the time that matters.
For the rest of the world, this shift away from GCPs is, as stated, being driven by the increasing capabilities and potential offered by RTK and PPK technology, especially as this technology is being developed and improved for aircraft use. The concept, as stated, is “a very simple concept.” The increased geotagging possibilities that can be had while still in the air mean that the number of actual ground survey points that can be required can be reduced, though, of course, this is to say they can be required in some form or another. As one professional overview of the actual potential for accuracy that is possible with drone technology itself states, Drone photogrammetry is capable of delivering sub-centimeter accuracy, depending on the environment and flight strategy. The results are still heavily dependent on the control strategy, processing, and verification.
In this regard, the results of the tests announced by Wingtra are perhaps slightly more interesting than the announcement itself, as the company goes on to explain in the announcement that, in fact, the most recent white paper investigated the results of 102 different flights, each and every one of which was conducted across one of five different locations, 95 percent of which were still within the sub-3-centimeter accuracy band via the use of checkpoints. The company goes on to explain, This was true notwithstanding a range of different software stacks, including Propeller, PIX4Dmatic, Agisoft, and Trimble TBC, as well as winter conditions, differing units of the aircraft and payload, as well as differing software stacks. As perhaps might be expected, the benefits are quite clear, and the company goes on to explain, For instance, while it can take four hours to survey a 50-acre site, it is possible to do so in as little as 40 minutes, while volumetric surveys can reduce possible errors by as much as 70 percent.
And then, of course, there is the regulatory level. According to Wingtra, The system is cleared by the FAA for flights over people with Category 3 parachute configuration and is eligible for collision avoidance and Blue List status for federally funded projects. So, the launch of the payload is more than an issue with the sensor. It is an indication of the way in which drone survey is moving from an image quality issue to a systems issue.
For those for whom “GCP-free” is still a too-vaguely-promised future, fewer GCPs, better airborne positioning, and checkpoint control is no longer a niche solution, but rather the standard solution for those who need to use survey data more often than they need to stake out the ground.