Product: These lidar data are processed Classified LAS 1.4 files, formatted to 22,802 individual 2000 US survey feet x 2000 US survey feet tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.  
	  Geographic Extent: USGS_IL_SouthCentral_2_2021 Illinois, covering approximately 3,260 square miles.
	 Dataset Description: USGS_IL_SouthCentral_2_2021 Illinois 2021 Lidar project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.5 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 2020 rev A.  The data was developed based on a horizontal projection/datum of NAD83(2011), State Plane Illinois West, US survey feet, and a vertical datum of NAVD88 (GEOID18), US survey feet.  Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 22,823 individual 2000 US survey feet x 2000 US survey feet tiles, 22,802 LAS files,as was tiled Intensity Imagery, and 22,823 tiled bare earth DEMs; all tiled to the same 2000 US survey feet x 2000 US survey feet schema.  Lidar point cloud LAS files are created for each tile in the tiling schema in which there is reflected photonic energy.  No LAS files are created for tiles in which there is total absorption of photons, such as tiles consisting of all water and in which photonic energy is absorbed. LAS files affected by photonic energy absorption are; 2555_7590, 2539_7210, 2539_7230, 2543_7190, 2543_7230, 2545_7230, 2545_7310, 2545_7330, 2547_7310, 2547_7330, 2547_7350, 2547_7370, 2547_7410, 2549_7330, 2549_7390, 2549_7410, 2551_7330, 2551_7350, 2551_7370, 2551_7410, 2555_7370. Intensity Images are created for each tile in the tiling schema in which there is reflected photonic energy.  No intensity tiles are created for tiles in which there is total absorption of photons, such as tiles consisting of all water and in which photonic energy is absorbed.  Stack emissions are present in the USGS_IL_SouthCentral_2_2021 project area, affecting tiles 2441_5890, 2441_5870, 2439_5870. These obscured areas are the result of aerosol clouds emitting from a plant and the LiDAR pulses were absorbed by the clouds.   
	 Ground Conditions:  Lidar was collected in spring 2021, while no snow was on the ground and rivers were at or below normal levels.  In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Subcontractor, Prairie Engineers established a total of 156 ground control points that were used to calibrate the lidar to known ground locations established throughout the USGS_IL_SouthCentral_2_2021, Illinois project area.  An additional 156 independent accuracy checkpoints, 88 in Bare Earth and Uraban landcovers (88 NVA points), 68 in tall Grass/tall weeds/crops, Brush lands/short trees, Forested categories (68 VVA points), were used to assess the vertical accuracy of the data.  These checkpoints were not used to calibrate or post process the data.
Product: These lidar data are processed Classified LAS 1.4 files, formatted to 22,802 individual 2000 US survey feet x 2000 US survey feet tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.  
	  Geographic Extent: USGS_IL_SouthCentral_2_2021 Illinois, covering approximately 3,260 square miles.
	 Dataset Description: USGS_IL_SouthCentral_2_2021 Illinois 2021 Lidar project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.5 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 2020 rev A.  The data was developed based on a horizontal projection/datum of NAD83(2011), State Plane Illinois West, US survey feet, and a vertical datum of NAVD88 (GEOID18), US survey feet.  Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 22,823 individual 2000 US survey feet x 2000 US survey feet tiles, 22,802 LAS files,as was tiled Intensity Imagery, and 22,823 tiled bare earth DEMs; all tiled to the same 2000 US survey feet x 2000 US survey feet schema.  Lidar point cloud LAS files are created for each tile in the tiling schema in which there is reflected photonic energy.  No LAS files are created for tiles in which there is total absorption of photons, such as tiles consisting of all water and in which photonic energy is absorbed. LAS files affected by photonic energy absorption are; 2555_7590, 2539_7210, 2539_7230, 2543_7190, 2543_7230, 2545_7230, 2545_7310, 2545_7330, 2547_7310, 2547_7330, 2547_7350, 2547_7370, 2547_7410, 2549_7330, 2549_7390, 2549_7410, 2551_7330, 2551_7350, 2551_7370, 2551_7410, 2555_7370. Intensity Images are created for each tile in the tiling schema in which there is reflected photonic energy.  No intensity tiles are created for tiles in which there is total absorption of photons, such as tiles consisting of all water and in which photonic energy is absorbed.  Stack emissions are present in the USGS_IL_SouthCentral_2_2021 project area, affecting tiles 2441_5890, 2441_5870, 2439_5870. These obscured areas are the result of aerosol clouds emitting from a plant and the LiDAR pulses were absorbed by the clouds.   
	 Ground Conditions:  Lidar was collected in spring 2021, while no snow was on the ground and rivers were at or below normal levels.  In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Subcontractor, Prairie Engineers established a total of 156 ground control points that were used to calibrate the lidar to known ground locations established throughout the USGS_IL_SouthCentral_2_2021, Illinois project area.  An additional 156 independent accuracy checkpoints, 88 in Bare Earth and Uraban landcovers (88 NVA points), 68 in tall Grass/tall weeds/crops, Brush lands/short trees, Forested categories (68 VVA points), were used to assess the vertical accuracy of the data.  These checkpoints were not used to calibrate or post process the data.
nan
nan
nan
nan