Falcon, masz jak zwykle ciekawy sposób dyskusji. Spadasz jak jastrząb, zrobisz komuś w locie kupę na głowę i odlatujesz.
Co powiesz na to co niżej? Cytat nie pochodzi ze stron rybnetu (z całym szacunkiem), tylko stąd:
http://www.pocketgps.co.uk/xtracornoxtrac.phpWydaje się, że jest to źródło nie gorsze od rybnetu, zaś informacje nieco bardziej aktualne od tych Twoich z 1996 roku.
How do conventional GPS Receivers operate ?
So I now understand that SiRFXTrac gives high sensitivity, but what does that translate to me and my GPS Receiver ? When you switch on your GPS Receiver, you will see a maximum of 12 satellites (12-all-in-view) out of around 28-29 Satellites that are live and orbiting the earth and fully functional. You don't see the remainder 16-17 satellites because they're physically out of view. They're probably on the other side of the earth from where you are at present, so you don't physically have a direct line of sight to these satellites. When we say direct line of sight, it doesn't mean that you can see them, but it does mean that you signals cannot be rebounded off of other objects like the sun, the moon, other satellites which aren't GPS. On an average day, many people will see themselves getting between 5-7 sats on average. You may only get 3 or 4, or you may get 8 or 9 sats. On a good day, if you're positioned correctly at the right time of the day, you can get to see a 11 or 12 sat fix, but it's fairly rare, the average is usually 5-7 sats. What the current SiRF chipsets do is hunt out the satellites and can quickly tell which satellites are being received weaker than others. When a satellite is high in the sky (e.g. above you) then you will get a very strong signal from the satellite. When a satellite is low on the horizon, it has a greater chance of having it's signal reduced by the earths ionosphere, and other objects that line the horizon like trees, buildings etc.
Normal GPS Receivers will hunt out the stronger signals and discard the weaker signals, so if you have 4 strong signals, and 3 weak signals, then the 3 weak signals will usually be discarded. How XTrac brings in better performance and possibly accuracy
The XTrac software/firmware basically acquires a fix on the stronger satellites first, but then continues to attack the weaker satellite signals to build a bigger picture, and works hard at bringing in a fix for the weaker satellites. This means that TTFF time can be extended in some cases or continuous, and due to this you may experience a brief lag on a map depending on the software you use when you are using your GPS Receiver in XTrac mode. But why bring in more satellites that are weak ? Well if you're in heavy foliage or in a covered car park, you will probably not be able to receive a fix.
If XTrac can sniff out the weaker signals and over time give you a better fix, then when you are under cover you may still be able to receive a fix. It's all about sensitivity.
So what is XTrac ?
XTrac is a firmware on the SiRF chipset that will boost the sensitivity of a GPS receiver. It does so by acquiring more signal from weaker satellites before it calculates your position.
For example, a normal GPS will acquire signals from 4 satellites with the strongest signals to calculate your position. In the XTrac mode, the GPS will acquire signals from 2 more weaker satellites (total 6 satellites) before outputting a position.Nie chce mi się szukać dalej, w dalszych czeluściach internetu.
Nawet jeśli powinienem dodać słowa "co najmniej", to nie zmienia to faktu, że żadnych herezji nie wypisuję. W przeciwieństwie do Ciebie.
[Dodano: 2005-04-12 00:42:45]
Falcon, masz jak zwykle ciekawy sposób dyskusji. Spadasz jak jastrząb, zrobisz komuś w locie kupę na głowę i odlatujesz.
Sorry, pomyliłem Cię z innym falconem. Nawet się zdziwiłem, że Ci wcięło avatara.
Tak czy inaczej, możesz już przyczesać zjeżony włos...