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|8th January 2007, 15:39||#31|
Senior - BHPian
Join Date: Sep 2006
Location: Melbourne, Hyd
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I meant how to decide, whether to deduct or add a percentage to get the actual speed of the car.
Can anyone answer my question without any assumptions or guessing?
Because, this would become important where speed limits are imposed.
What distance the GPS measure to calculate the speed?
1. Is it the distance travelled by the car's Center of Gravity? (OR)
2. The displacement from point A to point B. (displacement refers to shortest distance between A and B) I asked so because, i guess GPS uses satelites.
Last edited by kkr2k2 : 8th January 2007 at 15:41.
|8th January 2007, 16:56||#32|
Senior - BHPian
Join Date: Dec 2005
Location: Singapore, Mumbai, Nagpur
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you have to have a 10-12% difference in rolling circumference,
which translates to 10-12% difference in overall wheel diameter.
This is IMHO a huge difference, which practically impossible in real life!
Variations in tire size for any specific car are not that wild!
With big cars it's impossible, but even if we calculate for the dimunitive Maruti 800,
This will mean that
for a positive error of 10%, the standard 145/70R12 tire tread is worn down by 2.5 cm which is preposterous!
and for a negative error of 10%, the standard 145/70R12 tire is changed to 145/88R12 which again is preposterous!
or you're travelling close to the speed of light when the car length shortens (ref: Carl Sagan's TV show on Einstein's theory of relativity).
This makes sense in two cases.
Case 1: You are travelling in an absolutely straight line between measurements. Then displacement is identical to distance travelled.
Case 2: When the displacements measured are infinitesimally small.
This will be the case if you have a high-end aircraft GPS receiver-computer, which costs as much as the car itself, or if the car is creeping at a speed below 5 km/h.
|22nd January 2007, 16:46||#33|
Join Date: Jun 2006
Location: New Delhi
Thanked: 10 Times
Is this error also found in imported cars or only in indian cars ?? And if yes den wat percent (like in indian cars it is usually 10-12%).
I owe a Toyota Corolla 1985 model. My speedo shows 160 on full acceleration, so wats my actual speed at that time ??
Plz Advise .
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