Measuring with stick ruler or string ruler?

[763839]

whats more recognized as the right ruler to use?

 

[poptarts]

If you're curved string.

 

[jojolongdong]

whats more recognized as the right ruler to use?

A strip of paper too.
(Torn off an A4 sheet)

If you're curved & really small - A piece of elastic !

 

[erratic]

I don't think it matters, really. Unless you've got a curve like a doughnut, what's the difference going to amount to? A few millimetres?