which is more accurate

**yorkshireborn** · 26th August 2007, 15:14

been working today as a drivers m8 and the driver got flashed by a gatso now my sat nav gave his speed as 31 mph he said his speed when it flashed was 35mph. i know the van speedo allways says its faster than u are really going but the question is which is more accruate the speed camera or the sat nav.

**AL21784** · 26th August 2007, 15:23

going on the 2 sat nav's I've had, the sat nav always showed slower that what you was actually going, my 2 have both been about 4 mph slower than what the speedo says

**Inspektor** · 26th August 2007, 15:55

Sat nav is the more accurate AFAIK.

**ed taylor** · 26th August 2007, 16:30

I would say the sar nav is more accurate too. my car speedo is a few miles per hour faster than the sat nav, the same happens to my wifes Vectra too.

**chrisgettings** · 26th August 2007, 16:48

on average the sat nav will be around 2 to 6 mph running to slow.
it not the navi that's wrong it's just if info that they are aloud to show

you would need a true gps speedo and they don't come cheap but are spot on with the speed

dont trust your navi for your speed it needs time to work your speed out and it's also plotting your map to.
gps navi's plot in 5 meter zones
gps speedo's in 1 meter zones

**Flaninacupboard** · 26th August 2007, 17:21

If you are doing a constant speed the sat nav will be more accurate, if you are accelerating or decelerating your speedo will be more accurate.

**Duncan** · 26th August 2007, 17:30

SatNav will be more accurate for a constant speed. Speedos will always over read by a bit (which they are allowed to do up to 10&#37

but they are not allowed to under read by even 1mph - so the simple solution for car manufacturers is to have their speedos over read by a few mph. My speedo always reads a few mph more than my SatNav.

**Big-Pete** · 26th August 2007, 17:30

id say sat nav is more accurate, i spent 3months doing nights travelling from nr chelmsford to reading &there is an average speed camera system in the holmsdale tunnel while they are carrying out refurb work which is set at 40mph, my works astra shows 47 while my tomtom 910 shows 42, never had a ticket and i was in fast lane overtaking most others who thought they were doing 40 but according to tomtom they were travelling around 35 to 37mph. may have been lucky for 3months....

**Jamie** · 26th August 2007, 17:33

As the question is "Which is faster, the camera or the sat nav?"... the answer is THE CAMERA.

The camera uses RADAR technology to measure speed.

The sat nav is probably more accurate than the speedo though.

**Ste** · 26th August 2007, 21:50

If you really want to prove it, try driving a set distance of exactly one mile at exactly 60 mph on the sat nav (cruise on a flat motorway would be ideal) and see if it takes exactly one minute to travel it.

Then you will have the ultimate comparison - mathematics. You will then get a comparison to the speedo at that speed too.

But I would say the sat nav is more accurate than speedo, esp at higher speeds