In 2016, the Illinois Department of Transportation (IDOT) District 8 (D-8) had low distortion projections on NAD 83 prepared by Hutson and Associates, Inc. for the 11 counties within the district, which resulted in 9 zones being used for the 11 counties of D-8. Two pairs of counties share the same projection parameters. This collection of zones is to be known as the Illinois Coordinate System of 1983: 9 Zone. Adding a “District 8” supplemental reference to the name such as Illinois Coordinate System of 1983: 9 Zone (District 8) may be preferrable to users who have always referred to these projections as “the District 8 LDPs”. The terminology “Illinois Coordinate System of 1983” or “ICS83” is a combination of stating the datum is NAD 83 and the projection zone is defined for Illinois.

The ICS83: 9 Zone layer will not be recognized or supported by the National Geodetic Survey (NGS) which means that it will not appear in any of their published geodetic tools.  For this reason, the ISPCSC has developed a custom conversion tool named ILCAT to easily transform data between NAD 83 projections.  For information on this tool see the ILCAT page.