[Space] Fwd: KML from G1 data

Brian Choate brian.choate at gmail.com
Fri Jun 11 15:18:40 PDT 2010


The data that we have been talking about is from a G1 phone.

The GPS we are using with the radio equipment actually has software for
configuring those settings. I need to construct a programming cable for
the unit.

B.


On 06/11/2010 02:44 PM, tedward wrote:
> What GPS chipset are you guys using?
> 
> If you're using UBLOX, I wrote a little python tool that can speak its
> binary protocol and switch it to "airborne" filtering mode, which would
> avoid this kind of problem.
> 
> http://github.com/deleted/ublox
> 
> Cheers,
> twd
> 
> On Fri, Jun 11, 2010 at 1:49 PM, Erik Ebert <eebert at gmail.com
> <mailto:eebert at gmail.com>> wrote:
> 
>     More information from Ken, our club's GPS guru.
> 
>     I suspect that the weird stairstep ascent and descent you can see in
>     the Google Earth plot of the data is caused by the filtering issue
>     that Ken describes for "high altitude and/or high dynamic flights".
>     That's a typical symptom.
> 
> 
>     My guess is that what is going on is when the GPS is in 'ground mode'
>     and it sees a large change in altitude it assumes it must be a
>     multipath artifact and tries to smooth it out.  But when the altitude
>     change exceeds some threshold or goes on for long enough it decides
>     the altitude change must have been real and it resets the baseline to
>     the new value.
> 
>      -- Erik
> 
> 
>     ---------- Forwarded message ----------
>     From: Ken Biba <ken at bibafamily.com <mailto:ken at bibafamily.com>>
>     Date: Thu, Jun 10, 2010 at 10:09 AM
>     Subject: Re: [Space] KML from G1 data
>     To: Erik Ebert <eebert at gmail.com <mailto:eebert at gmail.com>>
> 
> 
>     Love to help.
> 
>     There are really two problems with GPS chipsets:
> 
>     1.  Some have a legacy limitation on speed and altitude - and I
>     suspect the Garmin had that problem.   There are legacy restrictions
>     on GPS from the old days (now expired) so the these devices would not
>     work to build missle guidance systems.    Now, since most of these
>     devices are built in China anyway - that is a pretty silly
>     restriction.   And further, they were often incompetently implemented
>     ... the restrictions were basically preventing a device from reporting
>     faster than the speed of sound AND above 60K'.     Sadly .. some folks
>     implemented OR rather than AND.   Confusion reigns.
> 
>     2.  A second problem, and somewhat distinct - is the filtering used in
>     the GPS microprocessor.    All of these devices use some kind of
>     filtering to improve their performance in changing environments.
>     Most are optimized for the GPS reception environment in urban canyons
>     on the ground (car and foot navigation) and make assumptions when
>     filtering consistent with that model.  Some - have multiple filters
>     supporting different movement models - the uBlox and the Trimble are
>     in the latter camp.
> 
>     I think Garmin no longer makes its own chipsets and uses SiRFStar
>     chipsets ... which would explain all of the above behaviour.
> 
>     The only chipsets that really should be used on high altitude and/or
>     high dynamic flights are uBlox or Trimble Lassen.     Trimble is
>     chipset used in Big Red Bee GPS.   Both need to be correctly
>     programmed (in non NMEA mode) to use the right movement filter.
>     Actually - that was the problem I think you had - BigRedBee had a
>     manufacturing glitch and forgot to properly program the GPS chip.
> 
>     Parrot is good ... so is GPSFlight ... frankly for their application,
>     I have 1W GPSFlight devices left over from the 100K project that
>     should work well.
> 
>     K
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> 
> 
> 
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