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Direct Geopositioning for Drones
Loki is AirGon’s third generation Global Navigation Satellite System (GNSS), Post-Process Kinematic (PPK) direct geopositioning system for drones. Unlike other direct geopositioning systems on the market today, Loki supports, in “plug and play” fashion, the ubiquitous Phantom 4 Pro and Inspire 2 drones from DJI. Loki turns these low-cost prosumer drones into high accuracy, professional mapping platforms. Of course, Loki also supports high-end drones equipped with digital cameras from Sony, Nikon and others.
What is Direct Geopositioning?
Direct Geopositioning is a technique in which high accuracy positioning equipment is flown on a drone to determine camera position estimates for the downstream processing software (PhotoScan, Pix4D, DroneDeploy etc.) that creates point clouds and ortho images. Direct geopositioning dramatically improves the horizontal and vertical accuracy of drone mapping projects, regardless of the project control strategy.
Direct geopositioning has a very rapid return on investment due to the hours of site labor that will be saved by reducing (or eliminating) the ground survey necessary to place control points. Direct geopositioning can also enable drone surveys where they were previously not possible due to the inaccessibility of areas for control placement (mine pits, islands, etc.). In short, everyone who does routine mapping using a camera-equipped drone will save money and improve results by using a direct geopositioning system.
We have teamed with Septentrio N. V. of Belgium to incorporate their state-of-the-art AsteRx-m2 multifrequency, multi-constellation differential carrier phase GNSS engine into Loki. The AsteRx-m2 is the most advanced small unmanned aerial systems GNSS receiver on the market today. Some of the more salient specifications include:
AirGon has implemented the AsteRx-m2 using third generation AirGon computational systems in a Post-Process Kinematic configuration. With a whopping 448 hardware channels and GPS/GLONASS enabled, Loki will track every satellite in the sky!
While the GNSS Engine is the heart of a direct geopositioning system, a lot of supporting electronics must be designed to realize an integrated, functioning solution. We have updated our second generation AirGon Sensor Package (ASP-2) with the new AsteRx-m2 GNSS engine and completely reworked our system board, camera event detection subsystem (we have a patent pending on this area of technology) and antenna interfaces. We have also made the system self-contained by adding a battery power subsystem. Finally, the entire system has been put on a pretty severe weight diet, enabling it to be easily carried by small drones such as the Phantom 4 Pro.
The network (“absolute”) accuracy that you can obtain with an aerial mapping system using PPK GNSS depends on a large number of factors such as the accuracy of the reference system, the camera calibration and so forth. That said, results can be quite good for typical site mapping. A recent test (“Wiregrass – 14 July 2017”) of Loki on an Inspire 2 with a calibrated X4S camera resulted in a planimetric ASPRS accuracy class of 4.0 cm and a vertical accuracy class of 6.5 cm - good enough for nearly any high accuracy mapping task!
What's in the Box
The Loki system (core and accessory kit) contains all of the hardware and software needed to implement direct geopositioning on a DJI Phantom 4 Pro/Inspire 2/M200 or a drone carrying a digital camera with a flash hot shoe such as Sony, Nikon, etc. You will need a GNSS base station for reference (not included) The kit includes:
The ASPSuite (Advanced Edition) includes all software needed to import support files, process the Loki observations in PPK mode and update image headers with the refined position information (an optional CSV file can also be output). We recommend LP360 (not included in the Loki kit) for debiasing point cloud data and performing horizontal/vertical accuracy assessments.
Loki outputs a priori X, Y, Z estimates (so-called “Given EO”) for any downstream software. However, some software vendors have specifically optimized their software to take advantage of information created by the AirGon Sensor Package Software Suite. As we roll out Loki, these vendors will be displaying the Loki Enabled logo. Insist on it when you make software buying decisions!!