MSHA - Code of Federal Regulations - 30 CFR 75.1200-2
30 CFR § 75.1200-2
Accuracy and scale of mine maps.
(a) The scale of mine maps submitted to the Secretary shall not be
less than 100 or more than 500 feet to the inch.
(b) Mine traverses shall be advanced by closed loop methods of
traversing or other equally accurate methods of traversing.
