Tex. Natural Resources Code § 21.071: ADOPTION OF COORDINATE SYSTEMS.

(a) The systems of plane coordinates which have been established by the National Oceanic Survey/National Geodetic Survey for defining and stating the positions or locations of points on the surface of the earth within the State of Texas are adopted and will be known and designated as the Texas Coordinate System of 1927 and the Texas Coordinate System of 1983.

(b) Each system is a separate system and must be used as a separate system.

Acts 1977, 65th Leg., p. 2357, ch. 871, art. I, Sec. 1, eff. Sept. 1, 1977. Amended by Acts 1987, 70th Leg., ch. 616, Sec. 3, eff. Sept. 1, 1987.