GPS for 911 calls

Harald Welte laforge at
Wed Mar 7 10:37:21 CET 2007

On Mon, Mar 05, 2007 at 06:56:08PM -0500, Perry E. Metzger wrote:
> Ian Stirling <openmoko at> writes:
> > Michael Welter wrote:
> >> What is the protocol for sending the GPS coordinates to the 911 dispatcher?
> >
> > I don't think there is one protocol.
> > Unfortunately, I suspect a 'say GPS coordinates' button on the 911
> > screen may be the most compatible way.
> Wireless Enhanced 911 for mobiles, including GPS or other
> radiolocation data, is a US standard. I don't know how the signaling
> works, but if you are selling a new phone in the US, it is mandatory
> that you comply.

Please see

"however. TDMA and GSM networks such as Cingular and T-Mobile use TDOA"
which is location singulation based purely on the network.  No device
support and no GPS needed for that.

- Harald Welte <laforge at>         
Software for the world's first truly open Free Software mobile phone

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