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.

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.

GNSS Engine

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:

• GPS L1, L2, L5 (enabled)
• GLONASS L1, L2, L3 (enabled)
• Support for Galileo, BeiDou, IRNSS, QZSS (optional)
• 448 Hardware Channels
• IONO+ advanced ionospheric correction
• APME+ multi-path mitigation

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!

Surround Technology

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.

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 Loki System Controller (including the Septentrio AsteRx-m2 GNSS Engine)
• Maxtena (M1227HCT-A2-SMA) L1/L2 GPS/GLONASS active GNSS antenna
• Loki Interface Cable
• Controller to antenna cable
• Charging/Data cable
• Mounting kit for your selected drone
• ASP Software Suite, Advanced Edition (1 Roaming license)

The ASP Software Suite (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 debaising point cloud data and performing horizontal/vertical accuracy assessments.


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 and no ground control 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!

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