simple 12v GPS speedometer

[v8dnw]

Does anybody make a basic GPS-based 12v speedometer? Just an aerial which plugs in to a simple matchbox-sized LCD box which gives vehicle speed. No speed camera warnings, no navigation, just speed.

Any ideas anyone?

Many thanks,

[AJLintern]

Not sure, but maybe a cheap alternative would be to use a wireless cycle computer

[combemarshal]

Might be worth having a browse here, www.pocketgpsworld.com
But why not get you speedo checked/calibrated, There is even a very slim chance it could be spot on, Only 1 vehicle I have ever driven has been spot on, My old 1.9td Xantia! (but my current 2.0t petrol one is out by about 10%!)
And I have never found a vehicle that is under the displayed speed

[Tripps]

combemarshal said:

There is even a very slim chance it could be spot on, Only 1 vehicle I have ever driven has been spot on, My old 1.9td Xantia! (but my current 2.0t petrol one is out by about 10%!)
And I have never found a vehicle that is under the displayed speed

I've always presumed that manufacturers err on the side of cuation by reading over to avoid speed tickets...

My first 1991 TVR is the only car I've had run spot on, everything else was over by some degree or more.

[owenemyr]

The majority of european cars over read speed by about 9%, and I have checked my various BMW's, Mercedes and Rover.
The legal requirment is that no speedo should under read 30 mph, but can be allowed up to 10% over read.
Some speedos are spot-on, but this may be a reflection of their country of origins legal requirement.
My corvettes are spot-on within the accuracy limits of my gps.
There are plenty of software that can be used as speed checks, (speed sentry etc) but all require essentially a pda and gps aerial.

[markmullen]

combemarshal said:

But why not get you speedo checked/calibrated

The difficulty is that as your tyres wear and your wheels become a different circumference then you'll go out of calibration, thats why police vehicles are calibrated frequently.

[Philbes]

According to my GPS the speedo in my car is +5% at all speeds up to 100mph (not checked in the UK!). My previous car was nearer 7% up to 70 and then inaccuracy increased until 10% at 100mph.

I haven't a clue as to the accuracy if speedos in earlier cars as I never checked them (although when driving a Cortina 1.6 the police claimed I was doing 106 when the speedo read less than 85!). If that was true it would have been the fastest Cortina 1.6 by a long way (and I was going uphill at the time!).