Using a steel tape to measure field events: doesn't the tape expand in the heat?

Thermal expansion is going to be less significant than the human error involved in the operator taking the measurements. There's a reason the measurements are taken 4-6" off the rail in lane 1 and nowhere else

And the baseline is "standard Reference conditions", which I don't know what the standards body is using but it's probably 70-90 with the coefficient of carbon steel expansion being 7.2x10-6 , any measurement would be recalculated to the standard reference condition except for one problem: human error is known to be greater than the coefficient of steel expansion so this factor drops out due to the need to carry only significant digits which represent the degree of accuracy +1

Steel tapes are calibrated to have the optimum measurement at 20 C (68 F) and of course the tape will expand or contract due to temperature. But the amount of change is negligible for the distances measured at a competition.

Even if it was 100 F , the correction over 100 meters would only be about 2 cm (approx 1 inch). For road measurements, we apply a "temperature correction factor" when laying out a "calibration course". But they tend to be 300-400 meters

I'm not sure what the other poster is talking about when he is referring to lane measurements

It seems no one actually read the title. OP is talking about measuring field events. You think 2cm doesn’t matter when measuring record attempts in the jumps and throws?? Really?

What field event is 100m long to have a 2 cm error?

JustAnotherRunner2001 wrote:

What field event is 100m long to have a 2 cm error?

Javelin is close.

In my spare time (very little of it), I've measured a few tracks in my area (Utica, NY area) with a rolo tape and some are actually off ~10cm per lane. At the place I work, it ranges about ~3cm-7cm per lane.

Jdjdjdndnd wrote:

It seems no one actually read the title. OP is talking about measuring field events. You think 2cm doesn’t matter when measuring record attempts in the jumps and throws?? Really?

Not when the temperature differential of the tape between competitors is negligible.

The practical effect for most field events is none. There's still a good reason why laser measurements are preferred, but a steel tape is still better than fiberglass.

In case you haven't noticed, there's margin of error in everything in life.

Sit and kick wrote:

Thermal expansion is going to be less significant than the human error involved in the operator taking the measurements. There's a reason the measurements are taken 4-6" off the rail in lane 1 and nowhere else

And the baseline is "standard Reference conditions", which I don't know what the standards body is using but it's probably 70-90 with the coefficient of carbon steel expansion being 7.2x10-6 , any measurement would be recalculated to the standard reference condition except for one problem: human error is known to be greater than the coefficient of steel expansion so this factor drops out due to the need to carry only significant digits which represent the degree of accuracy +1

This has to be one of the worst replies in letsrun history. Not only does it completely ignore the OP's question, it is pretty much incomprehensible yet actually looks like it took a lot of effort to write.

There are so many other variable when measuring field events that the temperature of the steel tape really does not play a factor. Obviously this includes the the placement of the end of the tape where the mark was made.

The IAAF does not require a temperature correction factor when using a steel tape for that reason.

how is that accurate? wrote:

On a hot day, wouldn't the steel measuring tape expand, thus leading to short measurements?

Yes, and there exist special tapes made out of an alloy called "ivar" that is formulate to have minimal thermal expansion. I don't know if these are required when measuring tracks but they do get in surveying when conditions suggest that a standard steel tape will not be accurate enough.

Just one additional item - if one really wanted to get closer to the true accuracy they would also need to use a spring scale to apply the correct force while pulling on the tape. None of this is required for field event track measurements. In the world of measuring common sense needs to be applied to reach "reasonable accuracy" depending on the application and variables.

Just get a calculator and use it to adjust the measurements, if it matters that much.

The EARTH also expands (because of global warming) which cancels out the expansion of the steel tape (whose mining from the earth caused said global warming)