[OSM-talk] Conflating Tracks - getting error margin from Garmin devices

[Karl Newman]

On Tue, Mar 10, 2009 at 8:44 AM, Ed Avis <eda at waniasset.com> wrote:

> Karl Newman <siliconfiend <at> gmail.com> writes:
>
> >>Are any of you aware of a conflation algorithm that "snaps" GPS tracks
> >>to the street grid?  This could be a useful way to verify existing
> >>road networks and fill in any gaps.
>
> >To do that you'd ideally want to know the margin of error for the GPS
> readings.
> >My GPS unit (Garmin eTrex Vista HCx) shows an error circle on its screen
>
> >I have a Vista HCx, too. Bafflingly, Garmin does not store the DOP with
> the
> >tracklog and there is no way to extract it after the fact (or even
> realtime, I
> >don't think).
>
> Oh, that is disappointing.
>
> >If you can get an NMEA stream, you can get the HDOP (which is what you
> care
> >about for this application). The USB-only Garmin units (like the Vista
> HCx)
> >cannot emit a NMEA stream like the serial-enabled units could.
>
> Apparently the Windows program GpsGate can convert the output from the USB
> Garmin devies to NMEA format.  I wonder if there is a free equivalent to
> get it
> working with gpsd or similar on Linux?
>

Well, GPSBabel is your cross-platform friend for translating between GPS
data formats, but my impression is that the Garmin USB protocol does not
contain DOP information. I would be happy if I were completely wrong on that
point, though.

Karl
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