Whats more accurate

[vc commodore]

GPS is more accurate, as it runs by satellites....Speedo variations occur due to rim/tyre assemblies, tread depth variations etc etc.

As for speeding fines in the mail...Who knows what you were doing, or if a few kays were taken from the initial reading....Unless you have a photographic memory, knowing exactly what speed you were doing by what device at that particular moment you got pinged. Time frames vary greatly as well...Anything from a week to 6 weeks, depending on whether you got picked up by a mobile unit, or fixed camera unit and how quick the employees are at processing the necessary paper work

 

[VFSV6FORME]

GPS is more accurate, as it runs by satellites....Speedo variations occur due to rim/tyre assemblies, tread depth variations etc etc.

As for speeding fines in the mail...Who knows what you were doing,

I have the Gamin set to beep 3 time if I go 1K over the speed so in a 60 Zone it goes off at 61 KPH, in 70 zone it beeps if you do 71 KPH and the same for 80 and 100. The system works when the Displayed speed on the left side of the Gamin (like a real speed sign)shows the area speed and in your setting you select to have warnings either 1 to 5 kmp hour to alert you with one or 3 beeps.

 

[John Revill]

Yes as the title says whats more accurate. A GPS or the VF Speedo
What do you think?

It depends on the quality of the GPS and whether accuracy or consistency is what you are after. The Speedo in the car will be more consistent, but usually read about 1-2% faster than your actual speed. So 100 on the dial is usually about 98-99 on the road. The accuracy of your GPS will depend on it's quality. Some GPSs have an accuracy of about 1-2 Meters and this can cause the speed to waver. The Speedo on the other hand will be very consistent and always out by the same about. Most GPS's in phones these days however are accurate enough to give a reasonably stable speed.

 

[vc commodore]

I have an elcheapo ebay special, that I bought about 4 years ago....(Have to check the name) It beeps when I go 5 kays over the designated speed limit for the area I am in.....So far, no "surprises" since I have been using it and I use it reguarly in a car that doesn't have an operating speedo





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[Skylarking]

The Australian Design Rules require a speedo to never display a speed that is lower than the actual speed.

This results in manufacturers being conservative and designing their speedo to indicate a lower speed than what is actually driven. That way you can never exceed the displayed speed if you drive according to the speedometer and posted spped zones.

How much lower a speedo actually reads as compared to the actuall speed travelled depends on how comforatable the manufacturer is with tyre options, tyre inflation and likely a number of other facters that can influence displayed speed verses actual road speed.

The aim is to always comply with design rules which means if you get booked for doing 63kph in a 60kph zone, you are likely traveling at 68kph as detected by laser while your speedo is indicating a road speed somewhere around 70 to maybe 75kph or more.

GPS is always accurate though it's update times may mean it's a little slow to display the actual speed while your accelerating so gives false readings during such times. A GPS display is absolutely accurate during steady state travel. In any case, because Australian Design Rules reference the vehicle speedometer, you can't reference what your GPS was showing in court as the judge simply wont want to entertain anything other than what your speedometer was showing and what the laser was showing, both being certified devices in the judges view (don't ask)...

 

[Forg]

The aim is to always comply with design rules which means if you get booked for doing 63kph in a 60kph zone, you are likely traveling at 68kph as detected by laser while your speedo is indicating a road speed somewhere around 70 to maybe 75kph or more.

In NSW, Qld & Vic they shave exactly 3km/h off the detected speed; if you get booked for 63 in a 60 zone, the detector read you at 66.
As you say, most likely the speedo’s saying something like 70 (it’s unlikely to read as high as 75; although it would meet ADR’s if it did).

GPS is always accurate though it's update times may mean it's a little slow to display the actual speed while your accelerating so gives false readings during such times. A GPS display is absolutely accurate during steady state travel.

Dunno what the VF’s built-in SatNav does, but aftermarket units have inbuilt accelerometers which are fairly accurate too; they take the last steady-state (which was fairly accurate) and they also know pretty accurately how much you changed direction, sped-up, slowed-down etc.
The VF’s SatNav must have accelerometers (or can maybe use the stability-control system’s hardware?) and not just use the speedo, because it does a fairly good job of tracking where we are in a tunnel such as the Sydney Harbour Tunnel or Lane Cove Tunnel, which have corners & are downhill/uphill.

 

[woooo]

So much incorrect information and guesses in this thread it’s laughable.

 

[kleanphil]

No , if gps is accurate and the tyre calculator is accurate then my numbers are correct ,the only conjecture is the speed limit trigger , and I have passed a roadside camera at atleast 2k over and not been pinged , so 3k is plausible . oh and please don't quote me on that

 

[Skylarking]

So much incorrect information and guesses in this thread it’s laughable.

So what incorrect information and guesses have been made? Do share, we can all do with a laugh

 

[Skylarking]

In NSW, Qld & Vic they shave exactly 3km/h off the detected speed; if you get booked for 63 in a 60 zone, the detector read you at 66.
As you say, most likely the speedo’s saying something like 70 (it’s unlikely to read as high as 75; although it would meet ADR’s if it did).


Dunno what the VF’s built-in SatNav does, but aftermarket units have inbuilt accelerometers which are fairly accurate too; they take the last steady-state (which was fairly accurate) and they also know pretty accurately how much you changed direction, sped-up, slowed-down etc.
The VF’s SatNav must have accelerometers (or can maybe use the stability-control system’s hardware?) and not just use the speedo, because it does a fairly good job of tracking where we are in a tunnel such as the Sydney Harbour Tunnel or Lane Cove Tunnel, which have corners & are downhill/uphill.

Yeah, i meant that device GUI processing can be slow to present information in some instances. By the time it gets around to presenting you the actual calculated speed, it's is sometimes already outdated information. Whether the speed was calcualted from giro or satalite could be irrelevant if the GUI takes a low priority than otehr tasks.

For example, my Navman usually tells me a specific rail costing is 200m away AFTER i pass it but that's because it's likley busy doing stuff of a higher priority (like trying to pinpoint satelites). Oddly, around that same area, it always tells me i'm doing 110kph while turning into the car park at 15kph.

The reality is that portable and current incar GPS units are not certified equipment and thus can't be used for life critical stuff unlike expensive aviation based systems. Guess that's why driverless cars seem to be more relyant on lidar and other vision systems to augment the lower quality GPS units used by the motor vehicle industry.

Still, i prefer to use my Navman to indicate my highway speed in preference the lower number displayed on my speedo or head up display