46 CFR § 69.207 - Measurements.
(a) All lengths and depths must be measured in a vertical plane at centerline and breadths must be measured in a line at right angles to that plane. All dimensions must be expressed in feet and inches to the nearest inch or in feet and tenths of a foot to the nearest tenth of a foot.
(c) The Coast Guard may verify dimensions of vessels measured under this subpart.
The following state regulations pages link to this page.