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Re: GPS as a speedometer

To: datsun-roadsters <datsun-roadsters@autox.team.net>
Subject: Re: GPS as a speedometer
From: RWM <RWM@rwmann.com>
Date: Fri, 14 Jul 2006 16:55:29 -0400
I use Mapopolis Nav maps on an HP hw6515 handheld PocketPC/GSM Phone/GPS 
unit in the car.  I like it.  Great maps, text to voice nav/directions 
and terrific navigation/reroute functionality.

When I first used it on long interstate stretches, I set the "barber 
pole" to 85 mph indicated, and set an aural speeding alert.  Overall, 
speed reporting was fairly consistent with speedo, albeit the update 
rate on the GPS is much slower than the mechanical speedo.

I quickly concluded the speed alert function wasn't going to work.

While it wasn't a constant annoyance, seemed every time a satellite 
dropped or added, or I passed a large sheet metal reflector (a.k.a. 
18-wheeler), it introduced enough of a momentary position error that the 
GPS inferred I was way past the speed alert limit.  Even happened a 
couple of times after decelerating and stopping at the gas pumps, for 
fueling...  Definitely gets your attention, though.

Then there was the time I forgot I had left it on departing National 
Airport.  Got some odd looks from fellow passengers as the aircraft 
accelerated, rotated and the handheld started squawking "Overspeed" 
while at my feet, in my briefcase.

- RWM



Jones Barton wrote:

> Hi everybody,
> 
> My speedometer is not working, I believe it to be something with the
> connection to the transmission.  My thought is I would have to work on this
> when the engine/transmission is pulled.  As I hope this won't be for sometime,
> I was pondering using a GPS mounted on the dash as a speedometer.  Has anyone
> done this?  Is the theory sound? Opinion as always are welcome.
> 
> Jones Barton
> Steilacoom WA
> 1969 1600




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