Nissan Car Lounge - Almera, Juke, Latio, Qashqai, Sylphy, Teana Owners > Latio
Speedometer "Error" on your Latio ?
LaChio:
--- Quote from: SoL on April 22, 2009, 11:04:01 PM ---Yup, bigger rims give false readings, slightly higher than normal.
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No, bigger rim doesn't mean higher reading than normal. It depends on the profile of the tyre you use and hence, the overall circumference. For example, the overall circumference of 205/50R16 is slightly smaller than the stock 185/60R15. So for those on 205/50R16, eg. when the speedometer shows 90kmh, actual speed is less than that. In this case, the GPS reading should be more accurate if you are cruising on a (more or less) constant speed.
SoL:
--- Quote from: LaChio on April 24, 2009, 01:37:35 PM ---No, bigger rim doesn't mean higher reading than normal. It depends on the profile of the tyre you use and hence, the overall circumference. For example, the overall circumference of 205/50R16 is slightly smaller than the stock 185/60R15. So for those on 205/50R16, eg. when the speedometer shows 90kmh, actual speed is less than that. In this case, the GPS reading should be more accurate if you are cruising on a (more or less) constant speed.
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I learned something new today! :thumbsup:
fickle:
--- Quote from: liewks on April 23, 2009, 05:51:11 PM ---Same here. Speedometer reading higher than GPS. I tend to believe that GPS numbers are correct. GPS readings tend to agree with some of the radar displays that LTA has set up.
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these days, i tend to go a lil bit faster than usual... :) hehe
liewks:
It is very unlikely that rounding errors in a double precision calculation would result in such a huge error. More likely, errors will be due to uncertainty in positioning.
Yes, if updates are too infrequent, then errors can result from deviations from straight line movement. But if you perform the experiment on a straight stretch of road, then such errors are miniscule and can be safely ignored.
GPS time is used to synchronise precision timebases. It is extremely accurate.
--- Quote from: Ying on April 23, 2009, 05:57:49 PM ---I believe the speedo meter give us speed measured from our wheels, The GPS give corrdinate only, the "speed" it gave is derived from a calculation. Using 2 coordinate divide the time taken it gives you displacement speed at most, the division it self will some some accuracy/round off problem. If one can spin the car, the speedo should have some reading but GPS give 0 kph.
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SoL:
GPS polling time should be fast enough to account for non linear distance bah. Im not too sure on how long between calculations though.
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