Inside GNSS Media & Research

SEP-OCT 2018

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26 InsideGNSS S E P T E M B E R / O C T O B E R 2 0 1 8 Spenko said, "One of the big implications [of aviation versus terrestrial safety] is that prior faults or errors are going to impact our current time safety. And that means if we do not have periodic updates from some absolute positioning sensor, our integrity risk is going to grow over time as we travel through a city." Imagine a vehicle starting at one end of a city and not having a GNSS signal or some other type of absolute positioning signal. As it drives through that city, its safety risk is going to grow and grow unless it gets some type of absolute po- sitioning. Guaranteed integrity, the measure of trust in a sensor's information, is important for ubiquitous robots. Correct association between features and landmarks require landmarks to be plentiful and well-separated, and these systems must remove ill-separated landmarks. SENSOR FUSION Hay's presentation delved deeper into autono- mous vehicle sensor fusion including the practi- cal considerations for the test and development of autonomous vehicle sensor characteristics and the pros and cons of each sensor type. He point- ed to Spenko's comment about the importance of keeping sensor information fresh whether range-based or absolute, and maps updated, and therefore, the role of connectivity. "We need all of these [absolute and range- based] sensors. There's value and purpose in relative positioning a vehicle with respect to known landmarks and objects on the roadway. And there's high importance in absolute local- ization or knowing where a vehicle is located with respect to a map that gives us a good per- spective to the road ahead," Hay said. WEBINAR RECAP ยป BEYOND GNSS THE PANELISTS Dr. Chaminda Basnayake Principal Engineer Market Development Locata Corporation Pty. Ltd. Matthew Spenko associate professor The Robotics Lab Illinois Institute of Technology Curtis Hay Technical Fellow General Motors GPS & Maps VEC East Demoz Gebre-Egziabher professor Aerospace Engineering & Mechanics, University of Minnesota Hay and GM have spent considerable time in recent years improving GNSS ability to achieve more precise localization by applying correc- tions. He highlighted GM's Cadillac Super Cruise, which incorporates a Level 2 solution that Hay said can achieve superior location performance by applying real-time clock orbit ionosphere and troposphere corrections to the raw observables from two constellations. The system combines the raw measurements from space with motion sensor information from the car such as yaw, roll, pitch and acceleration. They localize to a precise map by using all informa- tion from all sensors in the production vehicle to identify where the vehicle is in an absolute reference frame. "GNSS corrections are a really important part of maintaining a low probability of error and high accuracy required for absolute position. We receive today those corrections for SuperCruise through mobile IP which allow us to remove many of the effects of clock orbit and weather effects," Hay explained. "Once we know where the car is, we can perform the control functions such as path planning, trajectory control, steer- ing and braking." GNSS AND BEYOND Dr. Basnayake brought a slightly different per- spective to the webinar with his discussion about enabling autonomous machines with non-GNSS sensors such as Locata, a ground-based line-of- sight transmitter system. A network of small, ground-based transmitters (LocataNet) is currently used at the White Sands Missile Range as the core non-GPS positioning system for testing precision PNT with or without

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