Taking GPS devices out for a spin (Los Angeles Times)
According to the theory of relativity, due to their constant movement and height relative to the Earth-centered inertial reference frame, the clocks on the satellites are affected by their speed (special relativity) as well as their gravitational potential (general relativity). For the GPS satellites, general relativity predicts that the atomic clocks at GPS orbital altitudes will tick more rapidly, by about 45.9 microseconds (µs) per day, because they are in a weaker gravitational field than atomic clocks on Earth's surface. Special relativity predicts that atomic clocks moving at GPS orbital speeds will tick more slowly than stationary ground clocks by about 7.2 µs per day. When combined, the discrepancy is about 38 microseconds per day; a difference of 4.465 parts in 1010.. To account for this, the frequency standard onboard each satellite is given a rate offset prior to launch, making it run slightly slower than the desired frequency on Earth; specifically, at 10.22999999543 MHz instead of 10.23 MHz.
Taking GPS devices out for a spin (Los Angeles Times)
Still getting lost in the city? Your car must not have a new, wafer-thin, touch-screen global positioning system device. If it did, you would not only find your way around, you would also receive re First look : The Nav300 from Delphi has two key improvements over an earlier version. An external microphone lets you verbally request directions to one of several pre-programmed destinations. (To ...
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. GPS units top many gift lists (Tulsa World)
This year, GPS navigation units will top many Christmas wish lists. Global Positioning System units are ideal for heavy travelers, commuters and those who get lost frequently.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. Windows CE powers budget GPS devices (WindowsForDevices)
— Nov. 15, 2007 — Pharos has introduced two new GPS systems based on Windows CE 4.2. The Pharos Drive GPS 250 has a 4.3-inch touchscreen display, while the technically similar GPS 150 has a 3.9-inch screen, ...
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. Tempting target for thieves (Albany Times Union)
Albany police say a rash of vehicle break-ins in the city have a common link: GPS devices
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. TECHBITS: X-mas GPS, Plastic Wages, Video Antivirus (WABC-TV New York)
Santa may get a little help finding chimneys in Sweden this year: Global-positioning gadgets were designated the Nordic country's top Christmas gift for 2007.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. 'I could be dead now' (Casper Star-Tribune)
JACKSON (AP) -- A German man attempting to reach Yellowstone National Park with a GPS device says he nearly froze to death after his vehicle got stuck on a closed forest road.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. All I want for Christmas is . . . (Times Online Sunday)
Apple isn’t the first on the market with a media streamer, but that hasn’t stopped it making a device that will allow you to share the iTunes music, photos and videos on your television without the need to have your computer on.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. ARM9 SBC fits in 40-pin chip socket (WindowsForDevices)
— Nov. 21, 2007 — A Texas-based startup is shipping a tiny, low-cost ARM9 SBC (single-board computer) with an open hardware design.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. VS 2008 brings goodies, gotchas to embedded devs (WindowsForDevices)
— Nov. 20, 2007 — Following yesterday's release of Microsoft's Visual Studio 2008, more information has come to light about the impact on developers targeting the Microsoft's Windows Embedded OSes.
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved. Security bundle protects Windows Mobile device users (WindowsForDevices)
— Nov. 20, 2007 — Symantec has introduced a security software bundle aimed at consumers and small businesses using Windows Mobile smartphones. Norton Smartphone Security comprises Antivirus technology, a firewall, and an anti-spam feature for SMS (short message service). ...
Read full post here. Copyright (c) 2004 Yahoo! Inc. All rights reserved.
Taking GPS devices out for a spin (Los Angeles Times)
To measure the delay, the receiver compares the bit sequence received from the satellite with an internally generated version. By comparing the rising and trailing edges of the bit transitions, modern electronics can measure signal offset to within about 1% of a bit time, or approximately 10 nanoseconds for the C/A code. Since GPS signals propagate at the speed of light, this represents an error of about 3 meters. This is the minimum error possible using only the GPS C/A signal.
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