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Article: Self-Assisted GPS: no server, no connection requirement.(COMMUNICATIONS/TRANSPORTATION)
- Article from:
- GPS World
- Article date:
- September 1, 2008
- Author:
CopyrightCOPYRIGHT 2008 Questex Media Group, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Introducing a new method of generating an extended ephemeris where the entire algorithm runs on the PND itself, requiring no access to the Internet, ever. As a reference, the algorithm uses a recent, but expired, ephemeris for the satellites in view, and updates it using the known perturbing effects of the sun, moon, and Earth oblateness. Autonomous ephemeris prediction on the unconnected GPS or PND can then enable it to start up 5-10 seconds after being off for 1-3 days, rather than the traditional 30-second warm start that often stretches to many minutes in urban canyons.
The time-to-first-fix (TTFF) of a GPS receiver is dominated by the warm start, when new ...