Unmanned Systems Technology 011 | C-Astral Bramor ppX | IMUs | Autonomous farming | UAV Turbines UTP50R | London Show report | Advanced materials | Las Vegas Expo report

30 Dossier | C-Astral Bramor ppX Laser, C-Astral and Ventus Geospatial, a hyperspectral imager and a FLIR Systems thermal imager. With a specially modified lens of 30 or 19 mm focal length and a 24.3 megapixel (MP) focal plane array, the ppX’s RGB sensor is designed for sub- centimetre ground sampling distance (GSD) acquisition in survey-grade mapping, aerial photogrammetry and dense point-cloud data acquisition for digital terrain and surface models, and stockpile calculations. The CIR normalised difference vegetation index (NDVI) sensor, which is used to determine the presence, extent, type and health of vegetation, is also a Sony 24.3 MP APS-C format camera that acquires data in the NIR spectrum that can be processed into both NDVI and enhanced (eNDVI) pictures. Interchangeable with the RGB sensor, it can be used with multiple NIR and IR band filters. Along with the RGB or NDVI sensor, the ppX can also carry the lightweight MicaSense Parrot Sequoia MS-SQ multispectral camera. Self-calibrating with a sunshine (irradiance) sensor and an internal GPS, it has four narrowband filters tuned for crop health analysis and an integral 16 MP RGB imager for identifying anomalies in crops, for example, that warrant further investigation, a process known as digital scouting. With a GSD of 12.4 cm in mono and 2.7 cm in RGB, it captures one image per second. The multispectral sensor, a MicaSense RedEdge, simultaneously captures imagery in five spectral bands – blue, green, red, red edge and NIR – to create tailored indices for more sophisticated vegetation mapping applications. Its GSD is 8 cm per pixel at a height of 120 m above ground level and it captures one image per second, while its narrowband filters provide full resolution for each spectral band, as each has its own lens that can focus its light across the whole of the detector. Like its MS-SQ sibling, it calibrates itself using an irradiance sensor and an internal GPS receiver. For hyperspectral imaging in the 500- 900 nm wavelength range, C-Astral turned to Finnish company Rikola and its gHY camera developed for small UAVs. While 500-900 nm is the default spectral range, others are available, including 400-700, 450-800 and 500-950 nm. Spectral resolution is about 10 nm, which suits it to applications in agriculture, forestry and water research. The detector generates 2D spectral information in the visible to VNIR range with a single exposure, and enables the creation of photo mosaics with photogrammetric software. At the core of the camera is a 1024 x 1024-element CMV4000 CMOS sensor with pixels measuring 5.5 microns square, each of which covers a 6.5 cm square on the ground from a height of 100 m. The aperture is about f2.8 with a focal length of 9 mm and a 37° field of view. Another sensor option is the GasFinder, a laser mass spectrometer for pipeline and environmental monitoring that C-Astral developed in cooperation with Canadian companies Boreal Laser and Ventus Geospatial. The sensor will detect methane down to 0.005 parts per million (ppm) and the laser can be tuned to detect other gases such as carbon dioxide, carbon monoxide, hydrogen sulphide, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, ammonia, acetylene, ethylene and water vapour. The system consists of a laser transceiver in one winglet and a reflector on the other, with the transceiver linked by a fibre optic cable to an analyser in the fuselage. The laser beam forms the measurement path as it travels between the transceiver and the reflector across the UAV’s wingspan. The target gas absorbs a part of the laser’s spectrum, enabling the analyser to identify it and count every target molecule that crosses the measurement path to reveal an exact ppm concentration. Further development Trost says the airframe design of the ppX and other Bramor models can be scaled up to offer larger payloads and greater endurance, although it is smaller variants that are currently under development. Besides increasing endurance and payload capacity, other development work is focused on overall system user-friendliness, image quality and simplification of data processing. On the propulsion front, C-Astral is testing several options in addition to the solar panels, including batteries with higher energy densities and variable- pitch propellers. “In the second quarter of 2017 we will have the LRS system on the market,” Trost says. “We also have several ‘X’ projects in the works.” December/January 2017 | Unmanned Systems Technology This image of a quarry consists of a 3D point cloud geospatially registered with centimetric precision