Historically, Digital Elevation Model (DEM) data for Illinois have been mainly based on 5- to 10-foot contour data. Large-scale, digital topographic maps are most common; many data resources contain elevation information acquired in the 1920s and 1930s. DEM data collections are now being developed based on data with a contour resolution of 2 feet to 6 inches. A comparison between older data and newer high-resolution data shows remarkable improvement in recorded detail. ILHMP has established data sharing agreements to archive and distribute elevation data for select Illinois counties. Data have been acquired using Light Detection And Ranging (LiDAR) technology, in compliance with different contract specifications. Data are offered as originally deliver LAS tile or as the derivative product of DEM/DTM or DSM. Some helpful links: *LiDAR Glossary from the Applied Geomatics Research Group http://agrg.cogs.nscc.ca/resources/lidar-glossary/ LAS file format Spec Version is ---- Version 1.2, November 2014 http://pubs.usgs.gov/tm/11b4/ Status: Lidar Status for Illinois (pdf) Illinois LiDAR Plan 2021 (pdf) Illinois Lidar Acquisition By Year (pdf)https://clearinghouse.isgs.illinois.edu/data/elevation/illinois-height-modernization-ilhmpengIllinois Geospatial Data ClearinghousePublicHeight Modernization (ILHMP) LiDAR Data [Illinois])DatasetsIllinois