SURVEYING FOR AEC via free satellite-based augmentation services (SBAS), such as WAAS. But when the user activates a pre-purchased “token,” the full centimeter-precision capability, using external corrections, is enabled. “On the day of a UAS survey, we turn it on, activate a token from our account, and then we have 24 hours of high precision,” Schilling said. “It costs us $25 per day.” For two to three UAS surveys a month, this works out to far less over many years than the cost of buying a typical surveying rover. network. The Flex accommodates NTRIP connections to RTN or IP-enabled reference stations, but Bad Elf has added even more flexibility for corrections. In some scenarios there is no access to an RTN or no cell service (needed for NTRIP access). One option in these cases is to add a second Flex, set it up as an RTK base, and connect the base and rover via radios that Bad Elf offers. Bad Elf has added other options for corrections: the Bad Elf RTK service taps into a nationwide real-time network operated by Point One Navigation. This is accessible via NTRIP in the same manner as regional, state or local RTN, and is offered for a monthly fee. In addition, for situations where there is no RTN or cell service, a global precise point positioning (PPP) service (Atlas) can be enabled on the Flex. PPP differs from RTK/RTN in that it does not need the dense arrays of reference stations, or cell service to access. Instead, PPP derives very precise clock and orbit data from a global array of tracking stations and delivers this to the Flex via geostationary satellites. After a short convergence time, PPP from the Atlas service will yield 5 –10 cm precision over most of the globe. The Full Boat The City of Ellensburg, a college town and farming community in central Washington State, chose the Flex Extreme bundle for about $6,000 — the “full boat” configuration. The Extreme bundle enables all the add-on services all the time, eliminating the need for tokens. In their case, the frequency of use made the higher Correction Sources For real-time kinematic (RTK) corrections, Schilling connects via NTRIP to the statewide cooperative real-time network (RTN); sometimes in a network RTK mode (such as VRS) or single-base RTK to a nearby reference station on the same 0.02° RTK Roll/Pitch 0.06° 1 cm RTK/PPK Position RTK Heading QUANTA MICRO Outstanding Performance/ SWaP-C » Tactical grade IMU: 0.8°/h Gyro Biais Instability » Robust to Vibrating Environments » Post-processing with Qinertia PPK Software l.ead.me/gpsw2302 FEBRUARY 2023 | WWW.GPSWORLD.COM GPS WORLD 23
GPS World February 2023: Page 23
