Okla. Stat. tit. 60 § 1002
The plane coordinate values for a point on the earth's surface, used to express the geographic position or location of such point in the appropriate zone of this system, shall consist of two (2) distances expressed in U.S. Survey Feet and decimals of a foot when using the Oklahoma Coordinate System of 1927 and expressed in meters or U.S. Survey feet and decimals of a meter or U.S. Survey foot when using the Oklahoma Coordinate System of 1983 and expressed in International feet or meters and decimals of an International foot or meter when using the Oklahoma Plane Coordinate System (OKPCS). One of these distances, to be known as the "x-coordinate" (also known as "easting"), shall give the position in an east-and-west direction; the other, to be known as the "y-coordinate" (also known as "northing"), shall give the position in a north-and-south direction. These coordinates shall be made to depend on and conform to plane rectangular coordinate values derived from the National Spatial Reference System (NSRS) as defined and promulgated by the National Oceanic and Atmospheric Administration/National Geodetic Survey, or its successors, and whose plane coordinates have been computed on the systems defined in this act.
Okla. Stat. tit. 60, § 1002