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SiRF Takes the Start-up Wait Out of GPS Navigation, hvorfor SiRF fungerer mer effektivt
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Posta 26/1/2006 21:25 (#315)
Emne: SiRF Takes the Start-up Wait Out of GPS Navigation, hvorfor SiRF fungerer mer effektivt



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SiRFInstantFix eliminerer den første tidkrevende oppgaven med å hente presis GPS satellitt lokasjon data -- ephemerides -- fra selve satellittene. I stedet bruker SiRFInstantFix server et sofistikert sett av proprietære algoritmer for å forutsi sju dager med ephemerides og destillerer disse ned til et en liten fil som de SiRF-baserte navigasjonsystemene kan bruke til å lokalisere hver GPS satellitt. Ved å bruke SiRFInstantFix, kan dagens høy-effektive GPS mottakere ikke bare starte sporing og navigering mer hurtig, de kan også gjøre det med mye svakere satellitt signaler enn de som trengs for å innhente ephemeris data på den tradisjonelle måten. Dette fjerner barrieren som ofte står i veien for vellykket navigering under svake signal forhold.
Hele artikkelen, 25 January 2006:

SiRFInstantFix ensures Rapid, Robust First Fix, Removes Barrier to Weak-Signal Navigating

SAN JOSE, Calif., Jan. 25- Addressing the number one barrier to instant-on consumer GPS navigation systems, SiRF Technology, a leading provider of GPS-enabled silicon and premium software location platforms, today introduced SiRFInstantFix, a unique service that minimizes the start-up wait time for GPS systems. SiRFInstantFix provides consumers with the ability to turn on their SiRF-based navigation devices and achieve the first fix in as fast as eight seconds to begin navigating faster than ever before, even through urban canyons, under dense foliage and in other weak-signal conditions.

SiRFInstantFix eliminates the initial time-consuming task of obtaining precise GPS satellite location data -- ephemerides -- from the satellites themselves. Instead, the SiRFInstantFix server uses a sophisticated set of proprietary algorithms to predict seven days of ephemerides and distills them down to a small file which SiRF-based navigation systems can use to pinpoint every GPS satellite. Using SiRFInstantFix, today's high-performance GPS receivers can not only start tracking satellites and navigating more quickly, they can do it using signals much weaker than those needed to obtain ephemeris data the traditional way, removing the barrier that often stands in the way of successfully navigating under very weak signal conditions.

"Our customers in portable navigation and other applications are already starting to enable consumers to update a variety of information in their devices over the Internet using, for example, Bluetooth connectivity to mobile phones," said Kanwar Chadha, founder and vice president of marketing for SiRF Technology. "Now we can eliminate the long wait consumers complain about when first turning on their navigation systems and significantly improve the user experience, especially in obstructed environments, by synchronizing to SiRFInstantFix servers."

While in theory the determination of location using GPS satellites is a simple process of triangulation, the reality is more complex. First, the GPS receiver needs to know where each GPS satellite is with a very high degree of accuracy. Each satellite broadcasts its precise location once every 30 seconds, and the receiver must collect this data from every satellite it needs for a fix. If anything interrupts the signal while receiving this data, such as driving by a building or under a tree that momentarily blocks the signal, the receiver has to wait another 30 seconds until the information is broadcast again. In real-world conditions of urban canyons and dense foliage, where the GPS receiver is usually moving, it can often take several minutes to obtain all the ephemerides the receiver needs to perform its calculations and obtain a fix, resulting in a long period with a great deal of location uncertainty before navigation can begin. In some environments where the signal levels are very weak, the receivers may never be able to download this data reliably. Using weekly synchronization to SiRFInstantFix servers and downloading a small file, users can get much faster and more reliable fixes in most of the environments.

The SiRFInstantFix service implementation for SiRFstarIII-based product lines is available now to SiRF's customers.

SiRF source document
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