Measuring circuit lengths

[redshoes]

This may sound like a dumb question but it's something that's always bugged me - how do you measure the length of a circuit ? I assume you don't measure around the edge of the tarmac since the inner and outer edges will be very different in length. Is it maybe taken at the mid-point, half way between the inner and outer kerbs. Or should you use the 'racing line', which by definition 'should' be the shortest distance.

So what you may say. Well races timed to 0.001 sec and average speeds calculated to the nearest 0.01 mph. Over the course of a race the difference between the official distance covered and the actual distance means that trying to calculate averages that accurate is a bit of a waste.

[Crash Test]

I'll answer this one

This is what they do in Australia, but you would imagine that it would be the same worldwide.

If the bends in the racetrack go in the same direction, a line 900mm is to be drawn from the inside edge of the race track. If there are bends in opposite directions, they still measure 900mm out from the inside, and the two arcs around the bends are joined by a tangent. It has to be measured by a surveyor to the nearest 10mm.

[redshoes]

Thanks for that. So on a normal road course that equates to (sort of) the racing line, ie in a straight line between the apex of each bend. A little over-simplified admittedly.

On a simple oval, paricularly a banked one, that still makes quite a different as you're more likely to be driving high on the banking rather than close to teh inside edge of the track.

[GURRYP]

If you take this as a pure maths problem, then this is what you get.

For a circle of 250m radius you have a circumfrence of 1570m, if the track is 5m wide giving a radius of 255m then the circumfrence will be 1602m, a difference of 32m or approx 2%.

Obviously if you have an oval or road course the differnce could be considerably less or greater........

So I'm now more confused than I was before..........

Doh !! who cares............

[duckers]

I read about this on the CART website under technical regs, apprently you use the "FIA" method of the outside circumference of the circuit times inside circumference, divided by 2.

[redshoes]

You mean outside PLUS inside divided by 2, not outside TIMES inside surely. Think this is the same as taking the distance at the midpoint of the track.

GURRYP, that was my point. Depending on where you measure from there could be quite a difference.

[R]

And on an oval, if you drive high on the banking like redshoes said, it means that the actual race distance covered will be substantially more than, say, 200 or 500 miles?

Where a car drives on an oval will also have a huge effect on fuel strategy then. I haven't really thought about this before.

[Sparky]

I noticed on a Q&A section on Jayski.com that NASCAR determine the length of an oval by measuring 15 feet inside the outer wall.

Seems a strange figure, but it must be representative of the actual mileage covered, particularly as NASCAR races are described by their length. (As in 'The Ten-Tenths 500' )

[stevie.murray]

measuring outside and inside then adding the two distances then dividing by 2 sounds about right might give it a try see what we get.

[Schummy]

The (outside+inside)/2 method gives bigger length than the "australian" method formerly described. Can I assume the FIA official method is the averaged one and not the (pseudo)racing line one?

BTW, I can it's safe to say average between in and out sides are mathematically the same that length of middle line ("Yoong's line" ), that obviously is longer than racing line.