<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This Digital Surface Model (DSM) data was produced all or in part from LiDAR information as of 2014. The LiDAR derived DSM covers MadisonCounty, Illinois and include inland streams, rivers, lakes ponds and tidal features. These data are appropriate for use in local and regional analysis. This dataset was contracted as 2.21 ppsm LiDAR point cloud data. Madison County is approximately 966 square miles in central western Illinois. Data was collected at a nominal pulse spacing (NPS) of 0.67 meter. Data acquisition, processing and assessment is compliant with procedures and methods stated in U.S. Geological Survey National Geospatial Program LiDAR Base Specification Version 1.0 and Federal Emergency Management Agency Procedure Memorandum 61.</SPAN></P><P><SPAN /></P><P><SPAN>Digital Elevation Models (including terrain and surface models) are raster data sets created from whole LiDAR point cloud data sets (LAS files). The LAS files are the standard LiDAR file format which contains the raw point cloud data, these data are normally classified and distinguished between points on the ground, water or elevated features such as buildings, trees, towers, bridges, etc.. These LAS files are processed into elevation models to create gridded rasters. The first returns can be used to map the top reflective surface (Digital Surface Models - DSM), these normally include open terrain areas, as well as the tops of buildings, trees, towers, and other features elevated above the bare earth. The last returns are used to map the bare-earth terrain (Digital Terrain Models - DTM), these are normally produced with irregularly-spaced points rather than the uniform grid structure of a Digital Elevation Model (DEM), Digital Terrain Models will often include breaklines to help define edges of water bodies.</SPAN></P></DIV></DIV></DIV>
<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This Digital Surface Model (DSM) data was produced all or in part from LiDAR information as of 2014. The LiDAR derived DSM covers MadisonCounty, Illinois and include inland streams, rivers, lakes ponds and tidal features. These data are appropriate for use in local and regional analysis. This dataset was contracted as 2.21 ppsm LiDAR point cloud data. Madison County is approximately 966 square miles in central western Illinois. Data was collected at a nominal pulse spacing (NPS) of 0.67 meter. Data acquisition, processing and assessment is compliant with procedures and methods stated in U.S. Geological Survey National Geospatial Program LiDAR Base Specification Version 1.0 and Federal Emergency Management Agency Procedure Memorandum 61.</SPAN></P><P><SPAN /></P><P><SPAN>Digital Elevation Models (including terrain and surface models) are raster data sets created from whole LiDAR point cloud data sets (LAS files). The LAS files are the standard LiDAR file format which contains the raw point cloud data, these data are normally classified and distinguished between points on the ground, water or elevated features such as buildings, trees, towers, bridges, etc.. These LAS files are processed into elevation models to create gridded rasters. The first returns can be used to map the top reflective surface (Digital Surface Models - DSM), these normally include open terrain areas, as well as the tops of buildings, trees, towers, and other features elevated above the bare earth. The last returns are used to map the bare-earth terrain (Digital Terrain Models - DTM), these are normally produced with irregularly-spaced points rather than the uniform grid structure of a Digital Elevation Model (DEM), Digital Terrain Models will often include breaklines to help define edges of water bodies.</SPAN></P></DIV></DIV></DIV>
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