maemo.org - Talk - gps lock in 2 seconds !!!!!!!

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- - gps lock in 2 seconds !!!!!!! (https://talk.maemo.org/showthread.php?t=56415)

Re: gps lock in 2 seconds !!!!!!!

WTF you guys must have dodgy gps then, as i get a lock on nokia maps pretty much instant on nokia maps and thats on 3g not wifi...

Re: gps lock in 2 seconds !!!!!!!

Quote:

Originally Posted by 9000 (Post 720178)

Because US adds noise to the reading for civilian GPS usage.

No, they stopped doing that in 2000, that made the civilian GPS market viable. Thank Bill Clinton for that.

http://en.wikipedia.org/wiki/Global_Positioning_System

Re: gps lock in 2 seconds !!!!!!!

Quote:

Originally Posted by Soppa (Post 720278)

I think this is more related to the fact that the location was based only on A-GPS reading (estimate based on cell towers) and there was no real GPS satellite lock. A-GPS location is a really rough estimate.

Inside my house, GPS positions me on the opposite side of the road sometimes. That'll be about 30m away. That's proper GPS with a few satellites locked, according to the GPS diagnostic application. When it's only based on cell towers it's usually 300-500m off.

Usually it's more accurate, but sometimes it does go quite far off. I've seen it occasionally when driving, too - the car is positioned off the side of the road, passing through houses :)

Re: gps lock in 2 seconds !!!!!!!

Quote:

Originally Posted by jjx (Post 788256)

This is quite normal -- inside a building, you usually only get indirect signals that have been bounced once or several times, which will of course add delays. Since GPS uses signal timing to calculate your position, this will mess with the result.

Quote:

Originally Posted by jjx (Post 788256)

Usually it's more accurate, but sometimes it does go quite far off. I've seen it occasionally when driving, too - the car is positioned off the side of the road, passing through houses :)

GPS precision varies with a lot of factors. Read up on DOP (Dilution Of Precision) to get all the sordid details ;) -- satellite constellation is one of them. If you drove the same route on a different time of day and/or another day a few weeks later, the reading might be spot on. This is where D-GPS (Differential GPS) comes in with receivers capable of it.

Regards,
Chris.