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mode, there will be a full manual control option – indeed, the company is using a standard short-range line-of-sight system in the flight test programme. This is a 5-10 km set-up, de Villiers says, with custom options for longer range missions. The system includes an antenna tracking base station in a single-operator Pelican case with a built-in screen. “Right now, for long-range data telemetry, we are using 800/900 MHz and are looking at encrypted data links for higher end clients who need them,” he says. Alti is considering providing a standard data link for command and control and video, but which again can be tailored to customer needs in terms of characteristics such as the frequencies used. The ground control station (GCS) itself is another area in which the company is still considering its options. The software will be a custom version of the QGC system outlined above, while the hardware could be supplied by Hungarian company Horus, which makes and customises a range of military flight cases, GCSs and antenna tracking systems. “We will offer a range of GCSs, and the client can also add onto the system as required,” de Villiers says. “Our 29 UAV development platform. “PX4 has the potential to become the backbone of the rapidly growing drone industry,” says Lorenz Meier, the doctoral computer science student at ETH Zurich, who initially created the software. “The PX4 software will be to drones what Android is to many smartphones.” PX4 is already in use aboard thousands of small UAVs, says ETH Zurich, and Meier argues that the partnership with Qualcomm will extend it to the next generation of unmanned vehicles, which will be capable of completing far more complex tasks and avoiding obstacles, so the software’s range of functions is being constantly enhanced. As open source software, PX4’s source code is freely available, and any unmanned vehicle manufacturer can tailor it to their own needs, as smartphone manufacturers can with Android, adding their own apps such as camera controllers. It enables UAVs to take off and land autonomously and follow moving targets, for example. Open source ground control PX4 works with the QGroundControl (QGC) mobile and desktop interface software used to configure the system and execute missions. Again initiated and largely developed by Meier, QGC is also open source software that also supports open standards and provides full ground station support to the PX4 flight stack and MAVLink data links, and runs on Windows, OS X, Linux and Android tablets. QGC provides 2D and 3D aerial maps with drag-and-drop waypoints, and supports Google Earth. It also allows in-flight manipulation of waypoints and vehicle parameters via an EEPROM chip, supports real-time plotting of sensor and telemetry data and plotting of sensor logs. It also supports the Universal Datagram Protocol (UDP), serial radio modem and mesh networks, and multiple autopilot types in addition to PX4-based systems. The MAVLink protocol supports up to 255 vehicles in parallel and allows custom messages to be added. PX4 also features several customisable software packages including obstacle detection and avoidance that links to the flight control package, along with visual inertial odometry, mapping, planning, simulation and virtual flight testing. “PX4 offers reliability, features, ease of use and so on at a favourable price point compared with other s ystems,” says de Villiers. “I can’t think of any real drawbacks with a PX4-based system for our platform or applications. Clients have the option to integrate payloads with the autopilot, write custom code and more.” Alti has developed its own flight control algorithms with the help of a team of software engineers based in Switzerland. GNSS options The company continues to look at different GNSS options for integration with the flight control system and, because the UAVs are used all over the world, solutions are likely to involve multi- GNSS receivers. However, they are also likely to be customer dependent, with de Villiers emphasising that comms will be tailored to the requirements of the customer and the payload. While most missions are likely to be flown in pre-programmed autonomous Unmanned Systems Technology | June/July 2016 Alti Transition | Dossier Integrated into the fuselage, the petrol engine drives the propeller directly and is fixed to the composite rear bulkhead using elastomeric anti-vibration mounts