Washington Revised Code Title 58. Boundaries and Plats § 58.20.145. Plane coordinates

(1) The plane coordinates of a point on the earth's surface, to be used in expressing the position or location of the point in the appropriate zone of the WPCS, consist of two distances, expressed in feet and decimals of a foot or meters and decimals of a meter, along with the metadata of the observations used to determine the coordinates. One of these distances, to be known as the “east x-coordinate,” must give the distance east of the Y axis; the other, to be known as the “north y-coordinate,” must give the distance north of the X axis. The Y axis of any zone must be parallel with the central meridian of that zone. The X axis of any zone must be at right angles to the central meridian of that zone.

(2) Height is the coordinate value of the vertical elements of the NSRS expressed as feet or meters and identified as ellipsoid height or orthometric height.