ZitatAlles anzeigen
Aided GPS
In an effort to drop the TTFF in general and particularly in poor visibility conditions, companies like Sirf and the privately owned Global Locate introduced mechanisms to help receivers in obtaining ephemeris data without the need for the usual wait associated with it.
Notice that there is a difference between Assisted and Aided GPS (both called AGPS to complicate things a bit). Aided GPS is "generally understood to be either ephemeris or almanac aiding". While Assisted GPS uses data from a wireless network infrastructure, sometimes down to location information itself based on the Cell ID from a mobile phone.
There is also a difference regarding where changes are made to provide this aid: at the control plane by modifying TCP/IP format within the actual wireless network infrastructure or at the user plane where no major upgrades are necessary and the distribution is made thru messages like SMS for example.
Global Locate uses Trimble survey grade reference receivers to build its own private reference network to "collect, format and redistribute live ephemeris". This data is then used to provide Long-Term Orbit (LTO) data based in orbit models that according to this PDF will provide very precise satellite ephemeris good for up to 10 days.
The HP 6500 PDA includes "Quick GPS Connection" software that makes use of Global Locate LTO data which can be obtained thru a cradle sync or downloaded from the Net. GpsPassion tested it against a SirfStarIII equiped receiver.
Motorola phones equipped with GPS receivers already make use of Sirf's SirfLoc servers through its iDEN (Integrated Digital Enhanced Network) to obtain aided information for fast fixes.
Sirf just announced InstantFix, a mechanism similar to that provided by Global Locate where users will be able to download ephemeris good for up to 7 days for use with their receivers. In the same week that Sirf announced this service, GlobalLocate announced two patents just obtained covering the generation and distribution of LTO data. Let's hope they figure out a way to work together.
One of the selling points from LTO vendors is that knowing "where to look" for a signal a GPS receiver can use a lot less power to keep track of its location, from very weak signals and even under very poor visibility conditions, including indoors.
GpsPassion has a comparison of the Cold Start and Hot Start times for several GPS receivers for PocketPC's. For more info on Global Locate check this article from GPSWorld.
If you want more details about the operation of the GPS satellites check here, here and here (PowerPoint slides).
Quelle: jeepx.blogspot.com
Wie ich darauf gekommen bin: Ich habe bei google Aided GPS eingegeben 
Was ist A-GPS?
ZitatOriginal geschrieben von ap0ll0
both called AGPS to complicate things a bit
Quelle: jeepx.blogspot.com
Wie ich darauf gekommen bin: Ich habe bei google Aided GPS eingegeben
Danke für die Antwort.
Aber was ist das A-GPS das bei Geräten von NOKIA angeboten wird?
Assisted GPS funktioniert nach diesem text nur in speziellen Netzen wo folgende Daten vorhanden sind:
"While Assisted GPS uses data from a wireless network infrastructure, sometimes down to location information itself based on the Cell ID from a mobile phone."
Hat die Cell ID denn standardgemäß geographische Koordinaten?
Der text schreibt weiter, daß es verschiedene Systeme für Aided GPS gibt: Trimble, HP 6500 PDA, Motorola, Sirf, Global Locate.
Müßen für die Ephemeriden Daten dann mit den Firmen Vertäge abgeschlossen werden um diese Daten zu erhalten? Kosten?
Es wäre schön wenn jemand der ein solches Gerät benutzt das mal hier beschreibt.
Sie haben noch kein Benutzerkonto auf unserer Seite? Registrieren Sie sich kostenlos und nehmen Sie an unserer Community teil!