2008 Cook County 1 ft. elevation contours for PLSS Township Area 20. Data is derived from 2008 lidar. If you plan on downloading this dataset it is recommended to use the File Geodatabase option. The shapefile format may not work for larger datasets.This layer contains polyline geometry displaying 1-foot contours for Cook County, Illinois. The 1-foot contours were interpolated from a Digital Terrain Model (DTM) that was created during 2009, for the Cook County Board of Commissioners, by the engineering firm, Merrick & Company (Merrick). (See "Cross Reference" in the Identification Information section of this metadata report for full citation information.) The 1-foot contours cover the extent of the Cook County corporate limits, plus a buffer of an additional three hundred feet (300'). The 1-foot contours described in this feature class reflect ground conditions on specific dates during 2008 and 2009. Those dates, which are associated with a data collection mission using a Light Detection and Ranging (LiDAR) system, are as follows: November 21-23, 25, 26, 28, 29, 2008; April 11-14 2009. This dataset meets National Map Accuracy Standards (NMAS) for 1:1,200 (1"=100') scale mapping and 1' contours. This dataset is projected using the Transverse Mercator map projection. The grid coordinate system used is the Illinois State Plane Coordinate System, East Zone (Zone Number Zone 3776, FIPS 1201), NAD83/97 HARN (horizontal datum), NAVD88 (vertical datum), with ground coordinates expressed in U.S. Survey Feet.