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|Source:||Kentucky Division of Geographic Information|
This layer represents the polygonal grids for available DEMs from LiDAR State of Kentucky. Users will have access to this layer in the side pane when a Location of Interest (LOI) is placed near available records. The grid polygons were downloaded from the Kentucky's Aerial Photography and Elevation Data Program then attributed with URLs linking to the DEM and metadata files within the specific tile. When the user selects a tile, the pop-up bubble will show all available data with year and direct FTP link.
Kentucky does not provide direct LiDAR point cloud downloads, only digital elevation models generated from collected LiDAR.
LiDAR was collected at a 1.0 meter point spacing for the entire project area while no snow was on the ground and rivers were at or below normal levels.
Raster DEMs were tested by Photo Science for both vertical and horizontal accuracy. All data is seamless from one tile to the next, no gaps or no data areas within the project area. The vertical unit of the data file is in decimal feet with 2-decimal point precision.
Applanix software was used in the post processing of the airborne GPS and inertial data that is critical to the positioning and orientation of the sensor during all flights. POSPac MMS provides the smoothed best estimate of trajectory (SBET) that is necessary for Optech's post processor to develop the point cloud from the LiDAR missions. The point cloud is the mathematical three dimensional collection of all returns from all laser pulses as determined from the aerial mission. At this point this data is ready for analysis, classification, and filtering to generate a bare earth surface model in which the above ground features are removed from the data set. The point cloud was manipulated within the Optech software; GeoCue, TerraScan, and TerraModeler software was used for the automated data classification, manual cleanup, and bare earth generation from this data. Project specific macros were used to classify the ground and to remove the side overlap between parallel flight lines. All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Buffered LAS files were created in GeoCue to provide overedge to the DEM creation. These tiles were then run through automated scripting within ArcMap to create the 5' DEM. Final DEM tiles were clipped to the tile boundary to provide a seamless dataset. ERDAS IMG files were then created as the project deliverable. A manual QA review of the tiles was completed in ArcMap to ensure full coverage with no gaps or slivers within the project area.