[DC 86]

There is another issue involved as well - the fact that the pool lanes are not necessarily identical distances. In fact, FINA permits tolerances of up to 3 centimeters between lanes:

http://www.fina.org/content/fr-2-swimming-pools

It's basically impossible for the pool wall to literally be perfectly straight without imperfections and variations, which is why times are only measured to 1/100th of a second even though technology permits us to be much more precise.

[DC 86]

There is another issue involved as well - the fact that the pool lanes are not necessarily identical distances. In fact, FINA permits tolerances of up to 3 centimeters between lanes:

http://www.fina.org/content/fr-2-swimming-pools

It's basically impossible for the pool wall to literally be perfectly straight without imperfections and variations, which is why times are only measured to 1/100th of a second even though technology permits us to be much more precise.