Some clarifications for the AGPS/SUPL/OMA threads in the OpenMoko list.

[Sean Moss-Pultz]

Guys,

These are comments from a Global Locate Engineer (NOT ME) from various
threads about GPS and related functionality. Hope this will help answer some
of your questions.

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> I fear AGPS from globallocal is a coockoo's egg - they anounced that
> their AGPS chips cost only 5 US$ - I fear they will make money with
> their AGPS server services
> http://www.globallocate.com/NETWORK/NET_AGPS_SERVER_Frameset.htm
> Like selling cheap printer or mobiles and make the money with ink
> or the phone tariff.

"<flame>What's wrong with making money?  Don't be afraid.  GL will use
the money to make an even better follow-up AGPS device so the next
OpenMoko AGPS product will be even better.</flame>"

"Sigh... The dream of any company.  To make money.  The SUPL server
market is very competitive. All the AGPS server protocols are standard.
SUPL servers are a bleeding edge service (soon to be low-cost commodity)
where adherence to the standards, performance, uptime, experience, and
reliability sells the service; not proprietary data."

> The globallocal answers on my questions are diffuse and the information
> that AGPS is not usable without globallocate server

"Apologies, the intended use of the RTCM data stream was not clear.  If
you could tunnel TCP/IP/SUPL through RTCM, then all the previous
discussions might make some sense. But you can't, hence the fuzziness
that was noticed."

> >  "Would be a RTCM 2.3 Typ 17 stream enough for AGPS?"
>
>  If it has a TCP/IP portal on the network side to reach LTO or
>  AGPS servers, and would need a NAL on the handset side to connect to the GPS
>  control stack.

"<<real answer here, not pie-in-the-sky "tunneling 'diffusion'
answers">>"

"NAL == Network Abstraction Layer.  Not worthwhile to create an NAL for
RTCM.
Instead use SUPL over TCP/IP.
Reconfigure the server address and restart the AGPS protocol stack if
you wish to talk to a different SUPL server."

"RTCM is only useful for differential GPS for ionospheric model
correction.
AGPS assists acquisition time and initial accuracy.
RTCM would help with accuracy only, but not the satellite acquisition.
RTCM is not quite as useful since SA was removed by Prez. Clinton."

> free routing possible, but what is the protocol of the AGPS data
> that the globallocal chip expect?

"Very standard stuff: the SUPL specification by OMA.  Works with any
standard SUPL server. OMA and SUPL are easily googled for more info."

> Maybe I don't know enough, but for me it smells like that Global Locate
> AGPS is only used with AGPS servers - and with the risk that this
> server knows the location of every globallocal user after connection.

"As said above, the AGPS standards and servers are completely
standards-compliant.
Global Locate participates in all the standard OMA/SUPL protocol tests
around the world."

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-Sean