With sufficient tension the sag is way smaller than the errors introduced elsewhere. Mathematically the wire follows a catenary line. I did some calculations and can ensure you that the sag doesn't affect the measurements. In case of very long distances the sag can be calculated and taken into account.
Neat technique, but how do you compensate for the sag in the wire/line due to gravity?
With sufficient tension the sag is way smaller than the errors introduced elsewhere.
Mathematically the wire follows a catenary line. I did some calculations and can ensure you that the sag doesn't affect the measurements. In case of very long distances the sag can be calculated and taken into account.
(Also, theres wire sag tables for this purpose. A search on practical machinist will put out a bit more information)