GPS and Accuracy

sviyer · 10-10-2006, 12:50 PM

Hello,

I often find my car speedo and the GPS unit showing different speed values?
I am confused which one to beleive??
I know that speedometers are over calibrated here in India atleast, but is the GPS precise?

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Ford Fusion +
HP iPAQ 6965

RedGTiVR6 · 10-10-2006, 01:04 PM

I'd go off of the car.

the GPS in the car takes a bit longer to read and calculate and talk with the satelites.

xBrady · 10-10-2006, 01:04 PM

So long as your GPS receiver has a good fix it is precise. But like you said, cars speedos report you as going faster than you are. I'd believe your GPS unit.

Quattro · 10-10-2006, 01:06 PM

yeah, I've noticed that my car reports about 2 mph higher then the gps output. I'd say it is pretty accurate, but the only prolem is that the gps outputs don't update as fast as your cars speedo.

RedGTiVR6 · 10-10-2006, 01:13 PM

which do you think would hold up in court?

car spedo or GPS speed?

My money is on the car.

jeffreyd_tx · 10-10-2006, 01:17 PM

Quote: Originally Posted by RedGTiVR6

which do you think would hold up in court?

car spedo or GPS speed?

My money is on the car.

My money is on the cops radar gun.

xBrady · 10-10-2006, 01:25 PM

Quote: Originally Posted by RedGTiVR6

which do you think would hold up in court?

car spedo or GPS speed?

My money is on the car.

Which will hold up in court has nothing to do with which is more accurate. If one of the concrete trucks is driving 90 miles an hour and kills someone from one of the customers of the GPS tracking company I work for than GPS. If the guy claims he was going 45 MPH and we have him going 90 MPH, they are going to use our reading.
For anyone else I doubt you telling a judge that you were really only going 25 MPH based on your cars speedo vs. telling him your GPS said you were going 25 MPH is going to make a difference.

xBrady · 10-10-2006, 01:26 PM

Quote: Originally Posted by jeffreyd_tx

My money is on the cops radar gun.

Crap, that took me a long time to reply (was doing something else in the middle.) But that is what I was getting at near the end of my last point.

allanak · 10-11-2006, 12:28 AM

Speedometer accuracy is pretty spot-on within a few percent. Changing the size of wheels/tires will obviously cause it to be a bit off though.

sviyer · 10-11-2006, 10:42 AM

Thanks for your replies everybody.

JonDubya · 10-11-2006, 11:16 AM

My gps loses accuracy as I speed up...kinda weird, didn't do that before when I had it hooked up to my laptop (now in carpc)...I think is a cpu/computation issue.

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