Yesterday, according to Google maps, I drove about 547 miles.
According to my milometer, I drove about 559 miles.
Assuming that I have not made an error in calculating the above figures, that seems to be a difference of about 2%. How is one to account for it - and which is more likely to be accurate?
(And a subsidiary question: which is the currently preferred usage - milometer or odometer?)
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I'd say 2% was very accurate.
I wonder what the difference would be between different makes of tyre and new compared to legal minimum. Back in the '70s I recall referring to a book that listed revolutions per mile for different tyres.
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probably because you couldn`t drive in a perfectly straight line, but were weaving ever so slightly between the kerb and central line, over 500 odd miles this "extra" distance will add up. Maybe...
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"probably because you couldn`t drive in a perfectly straight line, but were weaving ever so slightly between the kerb and central line, over 500 odd miles this "extra" distance will add up. Maybe..."
That reminds me of a post made some years ago by Mark, aka 'No FM2R', a few years ago - on Wednesday 16th August at 2006 09:52, to be precise.
www.honestjohn.co.uk/forum/post/index.htm?t=43965
:-)
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In the HJ topic someone mentions doing a lap of the M25 for the heck of it. I did that once, just for something to do. I'd still do it now if I were in the mood, and the fuel didn't cost a fortune, and I didn't have responsibilities at home, and I didn't live 120 miles away from the damn thing.
Back on topic, I've a feeling Google maps won't count yardage (metreage?) around roundabouts etc - rather it will know the distance between an arbitrary point at one end of each road and an arbitrary point at the other, and add them all together. Some potential for cumulative error there.
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For one thing, it depends on whereabouts on the (width of) the road the measurement is taken by Google maps ~ centreline of road, centreline of individual carriageway etc.
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the accurate truth is probably somewhere between your odometer, and google maps.
The map is measured in straight lines from point to point, probably about 10 - 20 metres apart along your route. Its called vectoring. Given that, the map route distance will never be as accurate as the actual route driven. But then your odometer is probably 2% out as well.
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Wouldn't Google maps be based on a level route, whereas driving up/down hills would increase the actual distance covered (sorry, haven't any "sine" tables available to calculate if it is signifcant).
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Ingenious, lancara. I hadn't thought of that. Since a fair number of those miles were done in the Highlands, that might account for part of the discrepancy.
Now, how do I find out if Google maps are based on a level route?
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Is your speedo optimistic?
If so it makes sense that the odometer would be by a similar amount.
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>> Ingenious, lancara. I hadn't thought of that. Since a fair number of those miles were
>> done in the Highlands, that might account for part of the discrepancy.
>>
>> Now, how do I find out if Google maps are based on a level route?
I am sure you have much better things to do with your life!
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if you want to be accurate use geodetic trigonometry , you will need the 6 figure map co-ordintes of your start and finish points, its probably what google maps use any way, i think they use the great circle criteria
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The tyre circumference is a very valid one. If my car is fitted with 15" wheels, then my distance to drive to work is 30.1 miles. With 16" wheels, this reduces to 29.4 miles.
With many people fitting varying sizes of alloys, albeit all approved for that particular vehicle, the differences ijn distance over a tank-full of fuel will be noticeable.
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>> The tyre circumference is a very valid one. If my car is fitted with 15"
>> wheels, then my distance to drive to work is 30.1 miles. With 16" wheels, this
>> reduces to 29.4 miles.
The relevant factor is the rolling radius of the tyres rather than the wheel size.
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Milometer (odometer) accuracy and Google maps - bathtub tom
