On Tue, 2005-01-25 at 14:21 -0500, Dave VanHorn wrote:
> >
> >That said, there is no doubt that the machines DO work most of the time
> >very well.
> 
> 
> My local department bought a few of those K band speed boards that display 
> your speed..
> 
> I decided to do some testing.
> 
> The target is a 1998 ford expedition, it certainly shouldn't have any 
> trouble seeing that, especially on such a long straight road, with no other 
> plausible targets in sight.
> 
> I just waited till a nice quiet time of night, and made speed runs 
> calibrating against my GPS.  At 40 MPH nominal, my displayed speed was 
> about 10 miles off, in both directions sometimes, and most times was at 
> least 3-5 miles off.
> 
> GPS guarantees 1MPH accuracy.

Well, first off who's to say those devices are anywhere near as accurate
as the guns the police use as real evidence?

Second, I'd have to say you hit an anomaly, perhaps that unit was just
faulty. In the few times I've done something relatively similar (I have
a GPS installed in my car with a small display that tells me my speed
according to GPS, so testing those things is pretty easy for me to do!),
the speed board was off by at most 1 or 2 kph, sometimes hi, sometimes
low, but always very close. I also confirmed that my cars speedometer
was smack on.

I even tried getting out of the car and rollerblading, and even there it
was quite accurate (had a hand held GPS, a different unit then in the
car, with me at the time to confirm my speed). It's range certainly
wasn't as good as with a car, but I guess I was reflecting enough RF to
let it get a reading.

As I said before, the devices aren't perfect, but a cop isn't going to
believe his/her gun when he/she points it at you going a visual 20mph
and the gun reads 50mph. TTYL

 

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