Inside Unmanned Systems

AUG-SEP 2017

Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.

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AIR ENVIRONMENTAL MONITORING 64 unmanned systems inside   August/September 2017 Above: Dead Tilapia along the banks of the Salton Sea. with a different drone system and YellowScan's newly launched Surveyor scanner, which pro- duced the definitive survey. In parallel, a survey was carried out by Formation Environmental using normal hand- held RTK with a base station and measured points. "That's ground truth," Roorda said, "the way they used to do it before we started getting out there with UAVs." The aim of the coordinated exercise was to be able to compare LiDAR directly against the baseline RTK data as well as the drone-based photogrammetry. Previous attempts to assess the condition of tillage near the Salton Sea using drone- based photogrammetry had already proven unsatisfactory. "With photogrammetry you have problems getting the accuracy required," Roorda said, "because the contrast of sand is quite low. Looking at the resulting digital sur- face models of these areas, it is very difficult to tell what sand is higher than the other as you get closer and closer." As described by Roorda, the test area com- prised a tilled section of the Salton Basin pla- ya, about 100 meters long by about 80 meters wide, at the southwestern edge of the Sea. The team used a DJI Matrice 600 Pro with the YellowScan Surveyor as the payload. After a few runs, Roorda said, they managed to get their battery turnaround time down to as low as six minutes. "We built our own 3-D ground control points on the spot by shoveling sand into Home Depot buckets and putting a bolt in the center of the top," he said. Flight paths were longitudinal to the tillage and three different combinations of f light pa- rameters were used: • 40 m altitude, speed 5 m/s and 40 m f light line separation; • 15 m altitude, speed 3 m/s and 15 m f light line separation; and • 5 m altitude, speed 5 m/s and 5 m f light line separation. "Compared against actual measurements from the RTK survey, the LiDAR survey we did at 15 meters of altitude delivered results that were extremely close to reality," Roorda report- ed, "with errors of less than one centimeter at the furrow bottoms and at the tops of the ridges." At the lower height of five meters, he said, there were incremental marginal improve- ments, "but because of the small f light line separation it was so slow, it would take so long to get anything done that you didn't really gain anything by f lying at five meters." Photo courtesy of Wikimedia Commons, DJI and YellowScan. ONCE UPON A TIME IN CALIFORNIA BY THE 1950S, THE REBORN SALTON SEA HAD BECOME A HIT. It was the place to be, the 'Riviera of California.' Glamorous hotels sprang up, and mansions were built with private boat launches, and an array of tourist attractions appeared, including vacation villages, boat rental desks and even miniature golf courses. But underneath the Sea's surface, strange and unexpected forces were at work, slowly transforming the friendly waters. Much of the marine life that had managed to live in the sea was being killed off by pollutants, high salt levels and strange algal blooms. Masses of dead fish washed onto the beaches and the smell of decay mingled with other unpleasant odors coming from the lake water itself. The Sea, though still lovely to look at, was no longer as attractive to boaters and to swimmers as it had once been, and even sitting near its shores with a cool drink in hand had lost some of its appeal. The high rollers eventually packed up their things and went away, and the ranks of tourists followed. The trade in 'the-Salton-Sea-as-a-place-to-be' had dried up, leaving the real Salton Sea, and a few resilient local inhabitants, to their own devices. Today, life continues, more quietly perhaps than it once did. The people who live near the Salton Sea remain optimistic and determined, and while the memories of bygone days may be fading, explorers can still find the physical traces, including any number of abandoned and crumbling structures, testaments to the Sea's golden heyday. "IT WAS ALL A MISTAKE. We created a sea in the middle of a desert. And what did we do then? We made a resort out of it! Frank Sinatra and all the Hollywood stars used to vacation down there. It was a big glitzy place." Tim Roorda, Juniper Unmanned

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