54 In operation | Skyfish M6 and M4 high-end photogrammetry, but it soon hit us that the kinds of 3Dmodels we aimed to create would also need incredibly highend cameras, and a similar calibre of flight tools for carrying them.” That led Skyfish to Sony, not only for its high-resolution cameras but also the level of support Sony could offer –which, for all practical purposes, seemed far higher to Pilskalns and his colleagues than that of DJI and other potential partners. Skyfish then began building its own UAVs, and soon had a complete UAS solution, integrating its choices of high-end sensors, IMUs, onboard computers andmore. “We then sought to build up a lot of knowledge about industrial photogrammetry,” Pilskalns says. “Each target for inspection and digital twinning will model differently, whether it’s a cell tower, a dam or a bridge, so we went out into the field with lots of different customers to model varying kinds of infrastructure. “That was key to understanding how to handle, sharpen and refine our 3D models, how best to integrate Sony’s cameras, and also what kinds of components were best for our aim of producing fine-grain digital twins. As the saying goes, ‘Garbage in, garbage out’, and that applies so strongly to photogrammetry. You need to put everything you can into capturing excellent photos and data in flight, and then understand how to combine it. “And we’ve been asked, ‘Well I’m using a Sony camera, why don’t I get the models you’re creating?’ We’ve uncovered about 50 little trade secrets along the way, some of them hardwarecentric, some of them in the software.” The company’s resulting speciality in cell tower inspections was showcased in 2022 during a competition arranged by NATE (the National Association of Tower Erectors), a US organisation representing cell tower builders, in which UAV companies were invited to show how precise they could generate 3D reconstructions of a given tower. Key to that was the question of whether any companies (be it through EO, IR, Lidar or other sensors) could provide a model so precise that NATE’s analysts could gauge the thicknesses of metal from it – that is, the metal on electrical boxes, antennas, structural components and so on – down to the sub-millimetre level. This calibre of photogrammetry was the bar set to determine whether NATE’s members should start switching from human inspectors to UAS inspections. If metal thicknesses can be judged from photography and 3Dmodels, the need for humans to climb the towers and inspect components first-hand is eliminated. Skyfish emerged as one of few competitors capable of capturing the thicknesses of metals across the target cell tower, not only of pre-existing componentry but also of various small metallic ‘Easter egg’ objects hidden by NATE across the structure. TheM6 andM4 The M6 is a hexacopter measuring 174 cm across and weighing 10.4 kg when empty, with a MTOW of 17.7 kg and a payload capacity of 5.4 kg. The M4 is a quadrotor measuring 129.5 cm across, weighing 3.8 kg when empty and 10.9 kg when fully loaded. The M6 can fly for 33 minutes and 47 seconds when carrying 1.87 kg (enough for a Sony A7R-IV camera and a Gremsy T3V3 gimbal), or up to 27 minutes and 51 seconds when carrying 4.54 kg. The M4 can achieve 38 minutes of flight with a 2 kg payload, or 53 minutes with 0.61 kg. Both are fitted with subsystems for optimising them for photogrammetry. For instance, their navigation systems are RTK-ready, with redundant antennas June/July 2023 | Uncrewed Systems Technology Skyfish’s OEM vehicles and data-gathering tools are the 17.7 kg M6 hexacopter (top) and the 11.8 kg M4 quadrotor. Both are battery-electric systems built predominantly from carbon composite and featuring redundant antennas
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