Inside GNSS Media & Research

NOV-DEC 2017

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20 Inside GNSS N O V E M B E R / D E C E M B E R 2 0 1 7 towers necessary to build a nationwide network like the one that AT&T has, like the one that Verizon has or like the one that our predecessor proposed." It was also too soon to offer details on antenna types, she said. "I can tell you that the antennas will be developed to protect GPS, but in terms of where we are with that, it's just too soon in the process to know exactly what the antenna will look like." FAA and Ligado Some antenna characteristics were available, she said, based on the company's work with the Federal Aviation Administration (FAA). at information included the antennas' downtilt angle and the height of the antennas as well as how tall the towers would be. "I think if you were to give us a representative high-density laydown of your towers — just in terms of a two dimensional, what kind of separation and maybe what kind of antenna height associated with that — we could use the antenna gain patterns from the FAA information and combine that with some of the testing results, including of some of the test results of the RTK receivers, in order to start getting a numerical handle on things," said board member John Betz of MITRE. at information is available in the FAA documentation, said Green, and the inter-site distance used in the FAA analysis was 433 meters between sites. "And as I said, the power levels were set to account for the aggregate effect of a network, right, so it isn't just each tower individually it's all of them all the way out to the horizon." Ken Alexander, chief scientific and technical advisor for satellite navigation systems at the FAA, who happened to be in the audience, described the agency's analysis at the request of the board. He said the FAA had reached out to RTCA, its standards-setting body for both technical and operational inputs regarding Ligado Networks' proposal. ose inputs, Alexander said, included their proposed assessment of the propagation models built upon earlier work done on the LightSquared proposal. "e FAA assessed the maximum power level that would protect GPS use by certified aircra receivers outside of a proposed assessment zone, he said. While GPS reception is not assured inside the zone, "the FAA-assessed maximum power level is consistent with the range of powers that Ms. Green has stated." Alexander said the FAA has not completed a compre- hensive assessment of the potential operational effects of the proposed assessment zones on all certified aircra receiver applications. ey are continuing to review potential impacts to non-certified, fixed-wing, helicopter and GPS receiver applications for unmanned aircra and the many other civil applications as part of the ongoing Adjacent Band Compat- ibility study" "We (the FAA) have no agreement with Ligado Networks but we have assessed a number that will be in the DoT report that is within the range that she (Green) spoke to," Alexander WASHINGTON VIEW Spring GPS and GNSS+ INS Training Watch our website for details. 557: Inertial Systems, Kalman Filtering, and GPS/INS Integration. Instructors: Dr. Alan Pue and Mr. Michael Vaujin. Immerse yourself in the fundamentals and practical implementations that fuse GPS receiver measurements with strapdown inertial navigation. 5 full days. 346: GPS/GNSS Operations for Engineers and Technical Professionals. Instructor: Dr. Chris Hegarty. A comprehensive introduction to GPS/GNSS system concepts, design and operation, plus an introduction to DGPS and Kalman filtering. 4 days. 122: GNSS Fundamentals and Enhancements. Instructor: Dr. Chris Hegarty. Take the first two days of 346 for a basic introduction to GPS/GNSS systems and operation. +1-703-256-8900 • 800-628-0885 Questions? Contact Carolyn McDonald at NavtechGPS brings you ... NovAtel OEM7™ Series GNSS Receivers With Your ONE source for GNSS products and solutions +1-703-256-8900 • 800-628-0885 L-Band and SPAN ® GNSS+INS functionality 555 available channels Multi-constellation, multi-frequency TerraStar™ ready for centimeter-level positioning Field upgradable to all OEM7 software options Note: Many NovAtel OEM6 receivers are being phased out and replaced by the OEM7 series. Please contact us for details. Interference Mitigation Coming this May to the DC Area!

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