Questions about GPS

[yuan_you]

I've a few questions about Treo pro's GPS:
1) It's a "traditional" GPS getting data from satellites or it works with GSM towers ?
2) it's always on and consumes battery ? if yes, how can I turn it off. or it's off automatically when the navigation software is closed ?
3) How does QuickGPS work ? it retrieves what kind of information from Internet ? How it can know where I am if I'm at a location where there are no satellite signals ?

Thanks.

Yuan

[acidhax]

Originally Posted by yuan_you

I've a few questions about Treo pro's GPS:
1) It's a "traditional" GPS getting data from satellites or it works with GSM towers ?
2) it's always on and consumes battery ? if yes, how can I turn it off. or it's off automatically when the navigation software is closed ?
3) How does QuickGPS work ? it retrieves what kind of information from Internet ? How it can know where I am if I'm at a location where there are no satellite signals ?

Thanks.

Yuan

1) Depending on the application -- It can be both.

2) It is not always on. Thanks to the .NET platform.

3) All GPS applications do is grab your coordinants according to the relative positions between multiple satellites. If you can't get a signal, well, you don't get a signal.

[yuan_you]

Thanks for your kind answer.
For 3), I know how usually a GPS works, but QuickGPS seems not a "usual" GPS, it doesn't use satellites, but connects only to Internet. Because it runs and retrieves data from Internet even before I use GPS for the first time (phone stopped, wifi enabled), so my location is unknown for him yet, and when I ran it, I'm at home without satellite signals, because when I then tried to launch the "real" navigation program, I had to hand my Tro pro out of windows to get signals. Because I stopped phone reception, it couldn't use GSM towers neither.
So my question remains: what does it retrieve from Internet?

[rdm]

Originally Posted by yuan_you

Thanks for your kind answer.
For 3), I know how usually a GPS works, but QuickGPS seems not a "usual" GPS, it doesn't use satellites, but connects only to Internet. Because it runs and retrieves data from Internet even before I use GPS for the first time (phone stopped, wifi enabled), so my location is unknown for him yet, and when I ran it, I'm at home without satellite signals, because when I then tried to launch the "real" navigation program, I had to hand my Tro pro out of windows to get signals. Because I stopped phone reception, it couldn't use GSM towers neither.
So my question remains: what does it retrieve from Internet?

almost no home gets satellite signals which require line of sight to the sky. so unless your home has got not roof at all no "traditional GPS" on any device is going to work .

To your question of what and why why the Pro is attempting a connection to the internet, it is because it will first try "assisted GPS", which is a combination of using information available through the network and the satellites, most usually the information from the networks is used to get a better initial fix on the satellites.

So what your Pro is trying to do with the internet connection is get some combination of current "ephemeris", "almanac", and or atomic time. It can get all these from the satellites alone, but this can take longer depending on when you last used the GPS. If you last used the GPS 15 minutes ago, all the information is fresh and current, if you last used it a week ago or flew across the country all the startup information is gone.

If you are in clear line of sight to the sky (outside!) and blocking internet connection you would find that the first time using the GPS could take 15 minutes to get a location and subsequent times would be between a couple of minutes to instant, with an average of less than a minute.

Adding the internet connection, through your carrier's data service or wifi would reduce, again when outside, the times to on average less than 15 seconds.

If the Pro cant get any four satellites, which generally produce a resolution of <10 meters, can also get a fix within 600 meters using mobile towers if set up correctly.