[aprssig] garmin gps and compass heading

[Richard Amirault]

----- Original Message ----- 
From: "Jan T. Pharo"
Subject: Re: [aprssig] garmin gps and compass heading


>
>>A GPS expects to be held, face up, with the "top" of the unit towards the
>>direction of travel.  For instance if you are in a car, moving forward, 
>>and
>>the GPS says that the next waypoint is 90 deg to the right.  THEN, if you
>>stop and backup the car WITHOUT moving the GPS in any way .. the GPS will
>>tell you that the waypoint is now 90 deg to the LEFT!! so long as the car 
>>is
>>still moving backwards.
>
> The GPS will show direction independently of its own orientation. It's
> the difference in its position (lat and long) that is significant. And
> at least my Garmins are telling me which way to turn related to how it
> is moving, not which end of the navigator happens to be "forward" in
> this movement.

Maybe .. but that was not what I was saying .. if you are using your GPS to 
either:
1. follow a "route" (a bunch of waypoints) or
2. arrive at a single waypoint

you will NOT get proper directions UNLESS the GPS is facing the proper 
direction ("forward")

Of course a GPS knows it's own position independant of orientation, but 
that's not the problem, the problem is telling you where (left, right, back, 
forward) the place is that you want to go.

Again these are with handheld GPS units, not hocky puck types .. I haven't 
tested those.
Richard Amirault              N1JDU
Boston, MA, USA          Go Fly A Kite