765 ILCS 225/7
For purposes of more precisely defining the Illinois Coordinate System the following definitions by the United States National Geodetic Survey are adopted:
The Illinois Coordinate System, East Zone, is based on the transverse Mercator projection of the North American Datum of 1983 (NAD 83) or the Clarke spheroid of 1866 (North American Datum of 1927) (NAD 27), having a central meridian of eighty-eight degrees and twenty minutes West (88
For purposes of more precisely defining the Illinois Coordinate System the following definitions by the United States National Geodetic Survey are adopted:
The Illinois Coordinate System, East Zone, is based on the transverse Mercator projection of the North American Datum of 1983 (NAD 83) or the Clarke spheroid of 1866 (North American Datum of 1927) (NAD 27), having a central meridian of eighty-eight degrees and twenty minutes West (88 =-20'W.) of Greenwich on which meridian the scale is set at one part in 40,000 too small. The origin of coordinates is at the intersection of the meridian eighty-eight degrees and twenty minutes West (88 =-20'W.) of Greenwich and thirty-six degrees and forty minutes North (36 =-40'N.) latitude. The origin is given the coordinates x = 300,000 meters (984,250.000 feet) and y = 0 meters for NAD 83 and x = 500,000 feet and y = 0 feet for the NAD 27.
The Illinois Coordinate System, West Zone, is based on the transverse Mercator projection of the North American Datum of 1983 (NAD 83) or the Clarke spheroid of 1866 North American Datum of 1927 (NAD 27), having a central meridian of ninety degrees and ten minutes West (90 =-10'W.) of Greenwich, on which meridian the scale is set at one part in 17,000 too small. The origin of coordinates is at the intersection of the meridian ninety degrees and ten minutes West (90 =-10'W.) of Greenwich and thirty-six degrees and forty minutes North (36 =-40'N.) latitude. The origin is given the coordinates x = 700,000 meters (2,296,583.333 feet) and y = 0 meters for NAD 83 and x = 500,000 feet and y = 0 feet for the NAD 27.
The position of the Illinois Coordinate System is as marked on the ground by monumented survey stations established in conformity with standards adopted by the United States National Geodetic Survey for second and higher order work, whose geodetic positions have been rigidly adjusted on the North American Datum (NAD 1927 or NAD 1983, or both), and whose coordinates have been computed on the system herein defined. Any such stations may be used for establishing a survey connection with the Illinois Coordinate System.
765 ILCS 225/7