Question about GPS

[beanboy89]

I have a G1 running stock, unrooted Android 1.6. I don't have any data tied to my plan (I must use WiFi for any data). If I enable the GPS satellite feature on the G1, does the phone pull GPS data from actual GPS satellites or does it use triangulation from cell towers?

Furthermore, I've noticed that when GPS is on, the GPS icon in the status bar only is on while in Google Maps, and it simply flashes (I guess it's looking for satellites?). I had this on for a few minutes, and the phone wasn't able to find my location. I was indoors, but I was right beside the window.

In general, how does the GPS work and how can I take advantage of it?

 

[kejlyCZ]

Android uses 2 methods to find a position:
1) GPS - position is acquired from GPS satellites (Settings / Location & security settings / Use GPS satellites)
2) A-GPS (assisted GPS) - position is gathered from mobile cells and Wi-Fi APs (Settings / Location & security settings / Use wireless networks) - this needs internet connection

GPS is turned on just when needed, so if you don't use navigation ore some GPS tools, icon doesn't appear. You can check with "GPS Test", how many satellites are in view (at least 3 or 4 are needed), sometimes it takes minutes to get fix.

Basically, GPS module receives signal from satellites and based on time needed to receive signal from satellite computes it's position. For GPS principles, see:
Global Positioning System - Wikipedia, the free encyclopedia

 

[fratermus]

the GPS is capable of doing triangulation ("aGPS"), but I think this requires data. the GPS will work fine without data thought it will take the normal about of time to get a fix and not the shorter aGPS time.

Turning GPS "on" is actually just enabling it to be turned on by apps. Maps turns it on, as you can see. My understanding is that when the GPS is enabled but not in use by software that it uses no extra juice.

My guess is that the phone hasn't gotten a sat lock in a while and needs to pull down the "almanac" from the birds. This can take several minuts (up to 45mins in extreme cases) but usually takes 5-10 mins of constant, uninterrupted, clear view of the sky.

Might want to load a standalone GPS app and watch the sat info as it loads up. Take the phone outside with a clear view of the sky and let it get a lock. After that it should be able to get a lock by a window without the trouble you're seeing now.

 

[beanboy89]

Thanks. I fired up WiFi, loaded Google Maps, turned on GPS, sat by a different window, and about a minute later the GPS was able to pinpoint my location.