Guest David.Andzy Posted July 24, 2012 Report Share Posted July 24, 2012 I have tried few apps that are showing current speed (SpeedView, iGo...), and it always shows me 5-10kmh less than real speed. For example, I'm going 60kmh it shows me 49kmh, or I'm going 100kmh and it shows me 94kmh... Why is that inaccurate? Link to comment Share on other sites More sharing options...
Guest warimation Posted July 24, 2012 Report Share Posted July 24, 2012 usualy GPS systems are more acurate than your car.. xD when you'r going at 120kmh in your car in reality ur just going at 110.. Link to comment Share on other sites More sharing options...
Guest C3C0 Posted July 24, 2012 Report Share Posted July 24, 2012 Yep. Odometers in cars are intentionally made to show more than you're actually going. I think there is a rule for that and car manufacturers must follow it. Link to comment Share on other sites More sharing options...
Guest David.Andzy Posted July 24, 2012 Report Share Posted July 24, 2012 I also taught that but i don't think that car speedo is 15kmh inaccurate :/. Ok if it is 5, but 15 is too much. When i'm going 70(car speedo), igo is showing 51-55... C'mon you can tell difference when you are going 70 or 50 :/. Link to comment Share on other sites More sharing options...
Guest aamiel Posted July 24, 2012 Report Share Posted July 24, 2012 (edited) Yep. Odometers in cars are intentionally made to show more than you're actually going. I think there is a rule for that and car manufacturers must follow it. Yes here in UK and I believe in all of Europe, speedos have to show between 100% and 110%+10km/h of your speed. They also rely on you inflating your tyres properly and not changing your wheels. Also, on phones, GPS timing is very inaccurate and location often is less accurate than 3m so speed calculation will be off. Edited July 24, 2012 by aamiel Link to comment Share on other sites More sharing options...
Guest crnadakm Posted July 24, 2012 Report Share Posted July 24, 2012 I have tried few apps that are showing current speed (SpeedView, iGo...), and it always shows me 5-10kmh less than real speed. For example, I'm going 60kmh it shows me 49kmh, or I'm going 100kmh and it shows me 94kmh... Why is that inaccurate? I used iGo this morning and it was accurate... Link to comment Share on other sites More sharing options...
Guest ukgnome Posted July 24, 2012 Report Share Posted July 24, 2012 I am sure you can search Google and come up with the precise answer, but I warn you it is very maths heavy. It involves the calculations of geostationary orbits, the speed of light and the curvature of the earth. The simplified version can be found here http://airandspace.si.edu/gps/work.html And the slightly more complicated version can be found here http://www.pocketgpsworld.com/howgpsworks.php I was unable to find the site with the maths behind it, but after reading these I think you will be as amazed as I am that GPS works at all. Link to comment Share on other sites More sharing options...
Guest razzmataz1478 Posted July 24, 2012 Report Share Posted July 24, 2012 GPS is very reliant on what's happening up in the atmosphere. Right now, GPS is accurate up to 10m, so that speed is definitely not going to be accurate, especially on cloudy days. On sunny days it is probably accurate to about 5m. This new 'Goliath' satellites will make GPS accurate up to 1m, but won't be active until around 2018 or somewhere around that time. Link to comment Share on other sites More sharing options...
Guest crnadakm Posted July 24, 2012 Report Share Posted July 24, 2012 I think there is a rule for thatand car manufacturers must follow it. Apart from Honda :D 8% to 10%. Most common comparison is on 100 kmph. If your speedometer is telling you 100, most likely you are going 92 km/h Link to comment Share on other sites More sharing options...
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