Re: [gpsd-users] Missing fixes

[Gary E. Miller]

Yo Deven!

On Tue, 20 Feb 2018 14:15:33 -0800
Deven Hickingbotham <address@hidden> wrote:

> >> I'll send the raw data directly to you.  10hz and 4hz.  
> > 
> > Please, list only.  I'm not the only one here, there are a lot of
> > interested lukers.
> >   
> 
> Sorry, didn't want to clog up everyone's email with large attachments.

People have pretty big inboxes these days.

> > Or, better to go u-blox binary.
> >   
> 
> Question regarding this:  the docs say "If your GPS has a native or 
> binary mode with better performance that gpsd knows how to speak,
> gpsd will autoconfigure that mode."

Depends, a lot, on the GPS.  For u-blox, some prefer NMEA, some prefer
binary, so gpsd treads lightly on the existing u-blox config.

Pretty common to use u-center for your config, then save it as default.
You can use 'gpsctl -b', but I find that is pretty flakey.  I've been
looking at that, and at a python u-blox tool.  Nothing ready to show.

> Does this mean that gpsd will automatically switch into binary mode
> when it connects to a "known" gps OR does it mean that if gpsd
> connects of a gps that is already in binary mode that gpsd will adapt
> accordingly?

The later.  gpsd will sens the u-blox mode, and may make a few adjustments,
depenindg on how it wasa compiled.  Diff distros compile it differently.

You can also change mode while gpsd is running: gpsctl -n and gpsctl -b.
But, as I said, it seems to be very flakey.


> > And do you really need 10Hz?  What can possibly happen at 10Hz?
> > Even the msall mass of a small drone can't change direction, much,
> > at that rate.
> >   
> 
> Yes.  The GPS is in a car traveling 125+ mph, or 183+ feet per
> second, or 18+ feet every GPS cycle.

Sure, it is fast, but how high is the rate of change?  Unless it
hits a brick wall you can predict pretty well from 4Hz.

Still, a fun test.  So, up the baud rate, go to u-blox binary.  You
may just be over running what the GPS can do.  Try running bare, no
gpsd running, and see if the 10Hz in the serial port is good.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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    "If you can’t measure it, you can’t improve it." - Lord Kelvin

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