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[aprssig] Re: GPS with compass

Wes Johnston aprs at kd4rdb.com
Wed Mar 30 19:00:44 UTC 2005

I shouldda said GPSmap 76S.  I guess I need to d/l the manual and read it.


Quoting KC2MMi <kc2mmi at verizon.net>:

> Wes-
>  The Garmin GPS 76 does not contain a compass. Very few units actually do.
> The compass "screen" on most GPSes (I'd say 99% of them) is just a rendering
> based on the course and bearing information the GPS computes from the
> satellites and cannot be trusted unless you are in fact moving.
>  The NMEA sentances provide for course, bearing, cross track error, and
> other directional information. It all depends on which NMEA sentences you
> are sending out, and which ones the receiver is capable of parsing. NMEA
> provides for real compass information from a dedicated compass unit as well.
> I don't know if the GPS "lies" and uses that data field, or sends
> separately, but since marine integrators can take both instruments without
> confusion, I suspect the 'real' compass strongs are different. You might
> want to look up the NMEA specs on line to be certain.
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