Assisted GPS

Assisted GPS

Assisted GPS, generally abbreviated as A-GPS, enhances the startup performance of a GPS satellite-based positioning system. It is used extensively with GPS-capable cellular phones as its development was accelerated by the U.S. FCC's 911 mandate making the location of a cell phone available to emergency call s. [cite web |url=http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=12287 |title=Assisted GPS: A Low-Infrastructure Approach |publisher=GPS World |date=March 1, 2002 |accessdate=2008-06-11]

Description

Conventional GPS has difficulty providing reliable positions in poor signal conditions. For example when surrounded by tall buildings (resulting in multipath), or when the satellite signals are weakened when a GPS device is indoors or under trees. Some newer receivers are better at handling these situations.

In addition, when first turned on in these conditions, some non-assisted GPS units may not be able to download the almanac and ephemeris information from the GPS satellites, rendering them unable to function until a clear signal can be received continuously for up to one minute.

An A-GPS receiver can address these problems in several ways, using an "assistance server":
*The assistance server can locate the phone roughly by which cell site it is connected to on the cellular network.
*The assistance server has a good satellite signal, and lots of computation power, so it can compare fragmentary signals relayed to it by cell phones, with the satellite signal it receives directly, and then inform the cell phone or emergency services of the cell phone's position.
*It can supply orbital data for the GPS satellites to the cell phone, enabling the cell phone to lock to the satellites when it otherwise could not, and autonomously calculate its position.
*By having accurate, surveyed coordinates for the cell site towers, it can have better knowledge of ionospheric conditions and other errors affecting the GPS signal than the cell phone alone, enabling more precise calculation of position. (See also Wide Area Augmentation System)As an additional benefit, it can reduce both the amount of CPU and programming required for a GPS phone by offloading most of the work onto the assistance server. (This is not a large amount for a basic GPS – many early GPSs utilized Intel 80386-class 16MHz CPUs or similar hardware.)

A typical A-GPS-enabled cell phone will use an internet connection to contact the assistance server. Alternatively, it may use standard non-assisted GPS, which is slower and less accurate, but does not lead to network charges for data traffic, which can be considerable. [ [http://www.cnet.com.au/mobilephones/phones/0,239025953,339281483,00.htm Watch out for data charges on your GPS phone] . CNET, August 2007] Some A-GPS solutions do not have the option of falling back to conventional GPS.Fact|date=August 2008

High Sensitivity GPS is an allied technology that addresses some of the same issues in a way that does not require additional infrastructure. However, unlike some forms of A-GPS, high sensitivity GPS cannot provide instant fixes when the phone has been off for some time.

Development

CSR is developing eGPS, which is claimed to have greatly improved performance over existing solutions.

ee also

*List of devices with Assisted GPS
*High Sensitivity GPS
*GNSS Augmentation
*Wide Area Augmentation System
*Differential GPS
*Inertial Navigation System

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Assisted GPS — ou A GPS est une technique de positionnement par satellites. L’A GPS a été introduit pour améliorer la réactivité du GPS d’où son nom de GPS assisté. Le système GPS repose sur une table d éphémérides des satellites (voir l article sur le GPS pour …   Wikipédia en Français

  • Assisted-GPS — Assisted Global Positioning System (A GPS, Unterstütztes Globales Positionssystem) ist ein Verfahren zur Übermittlung von Hilfsdaten über ein von GPS verschiedenes Übertragungsnetz zur schnelleren GPS Positionsbestimmung. Über eine separate… …   Deutsch Wikipedia

  • Assisted GPS — Assisted Global Positioning System (A GPS, Unterstütztes Globales Positionssystem) ist ein Verfahren zur Übermittlung von Hilfsdaten über ein von GPS verschiedenes Übertragungsnetz zur schnelleren GPS Positionsbestimmung. Über eine separate… …   Deutsch Wikipedia

  • Assisted GPS — …   Википедия

  • List of devices with Assisted GPS — List of devices with Assisted GPS:*Apple iPhone 3G [ [http://store.apple.com/us/browse/home/shop iphone/family/iphone Apple Store (U.S.) iPhone 3G ] ] *BlackBerry Bold [http://www.blackberry.com/blackberrybold/] *Eten Glofiish X500 *Eten Glofiish …   Wikipedia

  • GPS-Satellit — Die Artikel GPS Technologie und Global Positioning System überschneiden sich thematisch. Hilf mit, die Artikel besser voneinander abzugrenzen oder zu vereinigen. Beteilige dich dazu an der Diskussion über diese Überschneidungen. Bitte entferne… …   Deutsch Wikipedia

  • GPS Drawing — Die Artikel GPS Technologie und Global Positioning System überschneiden sich thematisch. Hilf mit, die Artikel besser voneinander abzugrenzen oder zu vereinigen. Beteilige dich dazu an der Diskussion über diese Überschneidungen. Bitte entferne… …   Deutsch Wikipedia

  • GPS navigation device — Bicycle navigation with Gosmore, an open source routing software, on a personal navigation assistant with free map data from OpenStreetMap. A GPS navigation device is any device that receives Global Positioning System (GPS) signals for the… …   Wikipedia

  • Assisted Global Positioning System — (A GPS, Unterstütztes Globales Positionierungssystem) ist ein Verfahren zur Übermittlung von Hilfsdaten über ein von GPS verschiedenes Übertragungsnetz zur genaueren und schnelleren GPS Positionsbestimmung. Über eine separate Datenverbindung,… …   Deutsch Wikipedia

  • GPS Asistido — GPS es un sistema satelital de posicionamiento. A GPS fue desarrollado e introducido para mejorar el funcionamiento del sistema. El acrónimo A GPS deriva de los términos ingleses Assisted Global Positioning System, es decir, GPS asistido, y se… …   Wikipedia Español

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”