GPS for a speedometer

[ribitch]

So i was in sports authority buying a garmin legend, and I was talking to the outdoors department guide about GPS. He was telling me a friend of his bought one and disconnected the speedometer cable from his car. The GPS unit is supposed to be accurate to a few feet (dependent on the number of visible satellites), so his speedometer should be pretty accurate.

HAs anyone else heard of people doing this? Its not the legalist thing to do, but it does keep the mileage off your car. I am suprised this is the first time i have ever heard of anyone doing it.

[chadlnc]

I use it as a speedometer on my motorcycle, but I have not disconnected the cable. Never heard of anyone doing this to keep the miles off. You just can't trust some people.

[bachviet]

It comes with a big fine and jail time if you unplug that speedometer/odometer.

[mechmike0034]

Mechanical (cable-driven) speedometers/odometers have gone the way of carburetors and ignition points in most all current vehicles.

Also, many vehicles, particularly those with digital electronic odometers, store the odometer data in the PCM. Disconnecting the cluster won't change the data. Disconnecting the vehicle speed sensor(s) just sets trouble codes and can disable ABS operation.

[johnnymk]

It's very accurate, and it's a great way to check your real speed if you go with different size tires.

In Pennsylvania, if you travel less than 5000 miles per year, you are exempt from emissions inspection, so that could come in handy with older vehicles with mechanical speedometers.

[look_ma]

I am with johnnymk about how descent gps is as a speedometer. But is does have its draw backs. For example it has lag, and you can only get your acurate speed when you keep a constant pace for atleast 3 seconds. At lower speeds percentage wise it will be less accurate, ie watch out for those 20 mph school zones.

[mixer107]

Isn't GPS also affected by bad weather and physical obstacles such as driving through a tunnel?

[look_ma]

tunnel yes, logically you do not have a clear view through the sky. Not that many tunnels around though (around me atleast). I am curious about the weather, i doubt it would have much of a effect though or else the army would be screwed everytime it rained/snowed and they were in battle.

Those pesky cable companies would like you to think your sat signal goes completely out everytime it rains too.

[guiseppewv]

Originally posted by look_ma
tunnel yes, logically you do not have a clear view through the sky. Not that many tunnels around though (around me atleast). I am curious about the weather, i doubt it would have much of a effect though or else the army would be screwed everytime it rained/snowed and they were in battle.

Those pesky cable companies would like you to think your sat signal goes completely out everytime it rains too.

You are correct, the army wouldn't use GPS if it wasn't all weather. GPS is an all weather technology, it just won't work in tunnels or inside all parking garages.

And I agree with you about the cable companies.

[shoeish]

I used my GPS on my motorcycle as the main speedometer. With the gearing change, my speedo had to indicate 100mph for me to go an actual 78mph.

Also handy on snowmobiles, boats, jetski's, and to calibrate speedometers in after tire/gear changes.