What is correct, Speedo or sat nav?

mikey72

sat navs are accurate on average.
Why do you think they're not?

Stephen_Leak

On my old Mondeo, the speedo' was 10% under (ie. 30mph on the dial, 27mph on the road. 70mph on the dial, 63mph on the road). On my new Fiesta, the speedo' is 3mph under (ie. 30mph on the dial, 27mph on the road. 70mph on the dial, 67mph on the road).

Gloomendoom

I have noticed that the sat nav's do have a bit of a delay in responding to changes in speed although, overall, they are very accurate.

Lum

Flyboy152 wrote: »

Wow, that is quite a margin of error. :eek:

Now think of the people who think they are enforcing the law by doing exactly "70" in the outside lane.

Strider590

Lum wrote: »

Now think of the people who think they are enforcing the law by doing exactly "70" in the outside lane.

Or 60 whilst mumbling "it's a limit, not a target" under their flat cap.

birkee

adouglasmhor wrote: »

#
There is a speedometer on your satnav, It is a meter the measures speed (and displays it) and that is what speedometer means (a bit obvious really) so you are covered as long as you are getting a signal and in the accuracy level (which you will be) they may be able to get you in a road tunnel though I suppose.
Corgis were a great bit of kit, 98c two stroke no gears, wee wheels no suspension.

Surely the sat nav is a calculator of speed? Not a vehicle linked indicator.

birkee

Lum wrote: »

Satnav doesn't count. For one it doesn't work on a dyno, second it doesn't work in tunnels or certain city centres.

I looked into this when I was converting my car (Japanese Import) before registering it in the UK as it's a requirement to have a speedo that reads in MPH. The rules explicitly exclude using GPS devices for this. Ended up going with a Defi VSD heads up display thingie hooked up to the speed wire going into the car's ECU. It's also interesting that the Defi is more accurate than the car's actual speedo despite both using the same source. Guess the arrow doesn't quite line up.

Thank you Lum.
Exactly my point. The speed indicator needs to be vehicle linked otherwise it's a calculator.

birkee

cyclonebri1 wrote: »

Point missed Birkee
Speeding is speeding, the feds have calibrated kit you/we don't end of

I'm afraid you lost me!..... What point missed?

You are required by law to have a working speed indicator that works within the prescribed tolerances, and my comment was, ... "let them catch you with a non working speedeometer then" with reference to someone saying you didn't "need a speedometer to indicate speed, as a sat nav will do the job".

Feds? I'm not in the USA!
"you / we end of "..... what does that mean?

birkee

Gloomendoom wrote: »

I have noticed that the sat nav's do have a bit of a delay in responding to changes in speed although, overall, they are very accurate.

Precisely. A quick burst on a bike to 80mph in a 30 zone, and back to 2mph quickly. Without a speedometer, what speed did you do?

Flyboy152

mikey72 wrote: »

sat navs are accurate on average.
Why do you think they're not?

Because "average" is not an accurate representation of real-time speed.