AGPS - protocol specs?

Nils Faerber nils.faerber at
Thu Mar 8 13:51:11 CET 2007

Ian Stirling schrieb:
> Nils Faerber wrote:
>> Hi!
>> I am interested in doing a little research on the AGPS part. As far as I
>> understood the used Hammerhead chip will dump out the more or less raw
>> GPS data into userland which will then need to be post-processed in
>> order to get the usual NMEA or whatever messages.
>> So, can OpenMoko provide at least somemore information about that chip
>> and especially its output?
> No, the chip is under NDA.

I do not care aout most of the chip, just the output format ;)

> has the current state of play.
> Basically, the satellite format is known, and not especially hard to
> decode especially if we also get NMEA (or whatever) output out of the
> supplied daemon at the same time to decode it.

You mean some kind of reverse engeneering trying to match the NMEA
output to the raw input?

> There is all sorts of wacky stuff - for example, peer-peer DGPS that can
> be done, where all stationary neos on charge with a GPS signal and a
> free internet connection contribute to a global ionospheric model.
> Then any Neo can connect to this model, download 200 bytes or so, and
> get +-0.3m (or better) position for a short while.

Also relative positioning can be made much more precise using the raw
data (AFAIK in the range of cm not m).

  nils faerber

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