Re: iPhone location

In article <1inrpq4.2c4qro1rg8bbuN%NEWS@xxxxxxxxxxxxxxxxxx>,
NEWS@xxxxxxxxxxxxxxxxxx (Roger Merriman) wrote:

Chris Ridd <chrisridd@xxxxxxx> wrote:

On 2008-09-23 07:58:03 +0100, Graeme Wood <Graeme.Wood@xxxxxxxxxxxxxxx>
said:

Richard Tobin wrote:
In article <6jqctbF4jnh9U1@xxxxxxxxxxxxxxxxxx>,
Chris Ridd <chrisridd@xxxxxxx> wrote:

No... if I understand it correctly the marker changes to a green dot
when it's using GPS (rather than just the phone transmitter or a wifi
network). It was showing a largeish circle centred on the house.

The big blue target circle is what I get on the iPod Touch, so
presumably it indicates WiFi rather than anything else, 'cos that's all
it has got.

On the iPhone the blue target circle appears to mean "phone signal
or wifi".

No it doesn't. It means that you have a GPS fix.

If you have the target circle, then you have a fix either by known WiFi
location (unlikely in this country) or by triangulation from cell tower
signal strength.

I was very pleasantly surprised how accurately my iPod Touch got my
location (obviously using WiFi). I'm in suburban SW London, so I'd
imagine the centre of any city would be even better.

it's pritty good, quite often down to where on the street i am, once out
of the M25 it starts to fall off though, back in wales it says useful
info like your in abergavenny....

At home mine was spot on, even tho' I'd only gone about 30 yards above
ground. At work when I first initialised it, it could not obtain my
location. Today it has a location, big blue circle, but it's about half
a mile out.

From Apple's description
<http://www.apple.com/iphone/features/gps.html>, this all makes sense...

In addition to A-GPS, iPhone 3G uses signals from GPS satellites, Wi-Fi hot
spots, and cellular towers to get the most accurate location fast. If GPS is
available, iPhone displays a blue GPS indicator. But if you¹re inside ?
without a clear line of sight to a GPS satellite ? iPhone finds you via
Wi-Fi. If you¹re not in range of a Wi-Fi hot spot, iPhone finds you using
cellular towers. And the size of a location circle tells you how accurately
iPhone is able to calculate that location: The smaller the circle, the more
accurate the location.

My circle at home was about the size of my house. My circle at work has
a radius of about a mile...

Kind regards,

Dave
.

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