While swimming pools in the higher latitudes are heated to a constant temperature which does not vary much, one wonders at what time of day the lengths are measured in pools in hot climates. Can the physical expansion of the pool be significant? Or does the cooling effect of the water evaporting take care of this? Expansion certainly has to be taken into account in relatively short lengths of other civil engineering structures such as bridges.
Since the actual lengths of swimming pools can be measured much more accurately than three centimetres, could not the appropriate body produce a correction factor for times in each pool so that records could be compared directly?