GPS soft baseband processing

Al Johnson openmoko at mazikeen.demon.co.uk
Sun Sep 7 12:19:44 CEST 2008


On Sunday 07 September 2008, Andy Green wrote:
> Somebody in the thread at some point said:
> | On 9/7/08, Flemming Richter Mikkelsen <quatrox at gmail.com> wrote:
> |>  "Our automatic geotagging technology solves these
> |>  problems. A fragment of RAW GPS RF data is captured
> |>  in 0.2 seconds and then stored alongside the digital image
> |>  and the processing is performed later on a PC. Because
> |>  we separate the GPS capture from the GPS processing,
> |>  our technology maintains the traditional "instamatic" user
> |>  experience we are all used to and then pulls consumers
> |>  to experience a far more interesting way to search and
> |>  share photographs later."
> |
> | Interesting.
> | Around 1995 I  used about the same technique to sync spectrometer
> | data to an external authoritative timesource ( in that case the DCF77
> | signal encoded into 10ms dataframes ) time recovery could achieve
> | better than 100us
>
> It sounds like a fine technique, but it pushes the whole issue into
> license of the host CPU software then.  They don't seem to mention if
> they provide it or it is liberally licensed, etc.

There appear to be several open source GPS projects around, including a few 
that do correlation in software.

http://sourceforge.net/project/showfiles.php?group_id=91538&package_id=271229
http://gnuradio.org/trac/wiki/GlobalPositioningSystem
http://gnuradio.org/trac/wiki/GlobalNavigationSatelliteSystem



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