Parallax error

the error of parallax comes from the misuse of measuring devices due to the person taking the measurement not positioning themselves correctly while taking measurements.

look at the following diagram

Which one of the spectators can best judge the winner of the race?

Why do you think they are in the right place ? What happens as the race runs ?

Now lets see what 3 different positions give us in terms of volume,

1 is read correctly,

A very good source for Systematic errors