Nav6

[Bahram]

Hi All,
A question for the technically minded, why is there discrepancy between the speed the Nav6 shows and the actual speed on the speedometer? I when I’m doing 30 mph, the Sat Nav shows 24. Does the Nav need calibrating?

 

[tanneman]

It is all to do with the rotation of the earth vs the positioning of the satellites. That said, there may not be any satellites and all lies to make us believe the earth is indeed flat. I, at a hazard would guess that the earth's rotation needs calibrating or you ether have to pick what is actually 30mph. Honestly officer.

 

[Bahram]

That’s what I love about this forum, there’s no limit to the wealth of knowledge on here.

 

[richardbd]

It is all to do with the rotation of the earth vs the positioning of the satellites. That said, there may not be any satellites and all lies to make us believe the earth is indeed flat. I, at a hazard would guess that the earth's rotation needs calibrating or you ether have to pick what is actually 30mph. Honestly officer.

More likely you’re doing 24mph and the bike’s speedo needs calibrating...

 

[tanneman]

More likely you’re doing 24mph and the bike’s speedo needs calibrating...

You are a fucking spoilsport aren't you.

 

[yofi]

Something definitely wrong there. You'd expect a true reading of 30 mph from the Nav and 28 mph from the speedo (all vehicles are calibrated at under the true speed to allow for errors, usually at 2 mph out at 30mph, 3 mph out at 60-80). Find one of those signs that records your speed, and test.

 

[BobT]

Something definitely wrong there. You'd expect a true reading of 30 mph from the Nav and 28 mph from the speedo (all vehicles are calibrated at under the true speed to allow for errors, usually at 2 mph out at 30mph, 3 mph out at 60-80). Find one of those signs that records your speed, and test.

Now that is funny.

 

[tanneman]

Something definitely wrong there. You'd expect a true reading of 30 mph from the Nav and 28 mph from the speedo (all vehicles are calibrated at under the true speed to allow for errors, usually at 2 mph out at 30mph, 3 mph out at 60-80). Find one of those signs that records your speed, and test.

10% is the allowable error. None of this what ifs. The speedo is not a calibrated instrument. What is funny is to use another uncalibrated device to test an error.

 

[SBD]

I would be very wary of using an instantaneous gps speed as a reference for the speedo.
Over maybe 10 or 20 minutes at a continuous motorway speed, I’d expect them to be in quite good agreement.

Oh yes, check your tyre pressures too.

 

[tanneman]

GPS continuously refreshes, ie the calculation or sampling rate is very high. It also depends on the no of satellites in the reception area and how far above the horizon they are to improve accuracy. No problem to reference to the GPS speed.

 

[Bahram]

Thank you all for your input.
I also tried it in my car with very similar result, so I think I'll go with Tanneman's theory about the earths gravitational pull.

 

[Bahram]

It did the same when I tried it in my car.

 

[trebor]

When going in a straight line, on a flat road, the sat nav speed will be pretty much accurate, this is the time to compare it with your speedo. Start going round bends, or up and down steep hills then you will see a bigger discrepancy between your GPS speed and the speedo.

 

[iandavid]

Hi All,
A question for the technically minded, why is there discrepancy between the speed the Nav6 shows and the actual speed on the speedometer? I when I’m doing 30 mph, the Sat Nav shows 24. Does the Nav need calibrating?

It's the 5G chip from your Covid Vaccine interfering with the Canbus Fluid making it less viscous. That causes it to circulate through the TFT at a greater speed than normal, hence the higher reading. All quite obvious if you think about it.

 

[Bubb]

It's the 5G chip from your Covid Vaccine interfering with the Canbus Fluid making it less viscous. That causes it to circulate through the TFT at a greater speed than normal, hence the higher reading. All quite obvious if you think about it.

Combined with the fact that the earth is a flat disc riding on the back of an elephant..... if the elephant hasn’t had a cr*p for a while, it affects the discrepancy between the flugall valve and the optivassom flange, and therefore the speed on you satNag fluctuates

 

[notagser]

Hi All,
A question for the technically minded, why is there discrepancy between the speed the Nav6 shows and the actual speed on the speedometer? I when I’m doing 30 mph, the Sat Nav shows 24. Does the Nav need calibrating?

How worn are your tyres? As the wheel diameter gets smaller as the tyres wear, the rotational wheel speed will need to increase to achieve a given road speed on the speedo, unless you overinflate the tyres to compensate for the wear......

 

[tanneman]

Thank you all for your input.
I also tried it in my car with very similar result, so I think I'll go with Tanneman's theory about the earths gravitational pull.

Just make sure you get your moneys worth with that pull.

 

[Bahram]

Not lucky enough to have a TFT.

 

[SBD]

GPS continuously refreshes, ie the calculation or sampling rate is very high. It also depends on the no of satellites in the reception area and how far above the horizon they are to improve accuracy. No problem to reference to the GPS speed.

Trouble is, it doesn’t. It sometimes refreshes frequently, and sometimes it can’t, buildings in the way, other interference, etc,and then when it does update, it’ll jump. That’s why I said “be wary”. Over a period of time, it’ll be ok, but don’t bet on an instantaneous reading.

 

[tanneman]

The refresh rate is 1Hz. You need at least 3 satellites to calculate position on a 2 dimensional surface, or 4 if in a 3 dimensional space.