xNAV550 in tank training simulator
Learning to work as a team takes both time and practice. But when you’re learning to operate a 60-ton Challenger 2 main battle tank, with an operating cost of roughly £800 per kilometre, there are limits to how much practice you can do. However, thanks to OxTS customer Minerva, and its Thunderbird tactical part-task training system, new tank crews can now hone their basic skills and learn to work together in nothing more than a humble 4×4— and for a fraction of the cost. In turn this means that time spent in real a Challenger 2 is much more effective when it comes.
The Thunderbird system, which has an xNAV550 at its heart, is a very simple concept. “What we initially did was to say we’ll turn the back of the vehicle into a fighting vehicle; so you sit at the controls from a real Challenger 2 and work out how to fight with other vehicles,” says David Harris from Minerva. “The idea was that guys could do their basic training. They’re not going to learn to shoot properly of course, but they’re going to learn to work as a team, navigate as a team and that sort of thing.”
The system Minerva created is remarkably effective. Easily installed in a normal 4×4 vehicle, the Thunderbird system comprises the real controls from a Challenger 2 tank with monitors hooked up to a networked computer. The computer is in turn linked to a government training and simulation programme called Virtual Battlespace 2, but unlike normal computer games, Virtual Battlespace 2 is a georeferenced virtual environment.
This means that whatever you can see from the 4×4’s windows, is mirrored in the virtual environment that’s shown on the monitors linked to Thunderbird, including roads, trees, buildings and hills. The only difference between the real-world view and the virtual one is that you can include enemies in the virtual one, and that’s how the new crews learn to work together.
Of course, the system can only work if it knows exactly where the 4×4 is and where it’s pointing—which is where OxTS comes in. “You can imagine it’s quite important when you’re pointing a gun,” explains David. “Even a few tenths of a degree makes a huge difference at two kilometres, and the xNAV is very good for azimuth data.” Interestingly, David says there isn’t a need to push the xNAV to its limits in terms of positional accuracy. “We’ve found that about half a meter is perfectly acceptable in this application and we can achieve that using SBAS corrections in the xNAV, which helps to keep things simple. We had some prior experience with IMU sensors and GPS solutions, but for this project we knew we needed a lot more fidelity and the xNAV has delivered that.”
Now that Thunderbird is a proven concept, Minerva is also looking at expanding its application to include several other landbased vehicle platforms such as the Warrior, Ajax and MIV. This has the benefit of allowing the military to experiment with a wide range of vehicles (even before they’re delivered), in order to discover the best way to exploit them.
– 2 cm accuracy RTK
– Dual antenna heading
– No export restrictions
– High-grade IMU for direct georeferencing
– xNAV < 425 g
– OEM board set version available
At the heart of the Thunderbird system is an xNAV550 GNSS aided inertial navigation system. This self-contained position measurement system provides a constant stream of position, orientation and velocity information output via an Ethernet interface, which is then used by the Thunderbird system to position the vehicle in the virtual environment. To increase the availability of satellites, Thunderbird uses a GLONASS enabled version of the xNAV.
While the xNAV can achieve 2 cm accuracy in real-time, that level of accuracy is not always required and in the case of the Thunderbird system, an accuracy of near to 50 cm was found to be adequate (maintaining accurate roll, pitch and heading accuracy was more important). To achieve this position accuracy in vehicles operating in large training areas, SBAS corrections are enabled in the GNSS receivers, although easily be applied from a local base station or NTRIP server.
> Roll pitch accuracy
Apart from the reliability of the measurement output during GNSS blackouts, one of the most appealing things about the xNAV550 for Minerva was the precision of its orientation measurements. While a dual antenna GPS system may have provided accurate heading information about the vehicle platform, it wouldn’t have been able to also measure the roll and pitch of the platform at the same time—something the xNAV does to hundredths of a degree.