This Model is intended as a basic example of how to use the Spatial Modeler to perform traditional "site selection" tasks based on different input data layers and various spatial operations. This example model finds candidate helicopter landing zone areas based on land cover and terrain input files. The model assumes that land cover class values are the standard USGS NLCD scheme and automatically picks "open" (i.e. not cluttered by vertical obstructions) classes for candidate areas. These candidate areas are then further constrained using the terrain file by looking for large and flat areas. User provided terrain processing parameters include maximum percent slope, minimum width in feet, and minimum area in acres.
Above: Model output overlaid on a backdrop image and related attribute table
Below: Calculate Percent Slope submodel
Below: Apply Minimum Width submodel
Below: Apply Minimum Area submodel
Below: Attach Colors and Attributes submodel
Input NLCD Land Cover: (filename with path) of the input raster file containing land cover classes. Model assumes that land cover class values are the standard USGS NLCD scheme and automatically picks open classes for candidate areas.
Input DEM Elevation File (DTED2 or similar): (filename with path) of a raster elevation model. Used in computing slope of candidate areas.
Output Helicopter Landing Zones: (filename with path) of the output raster file. This is a thematic raster file where value 1 (colored purple) shows areas that are suitable for helicopter landing zones and value 0 (colored transparent) are the remaining areas.
Input DEM Elevation Units: (unit picklist)(default Feet) Specifies the units used in the input DEM elevation file.
Maximum Percent Slope: (float)(default 7.0) Specifies the maximum slope (in percent slope). The model filters candidate regions by this value, ensuring that candidate areas are fairly flat.
Minimum Area Width in Feet: (float)(default 600.0) Specifies the minimum with of candidate areas.
Minimum Area Size in Acres: (float)(default 20.0) Specifies the minimum size of candidate areas.
The example data covers a part of north Georgia, just north of Atlanta.
nlcd_2006_landcover_subset_wgs84.img – Raster file containing USGS NLCD land cover classes. The model assumes that land cover class values are the standard USGS NLCD scheme and only files with this type of scheme are appropriate for this HLZ model.
dem_usgs_100_foot.img – Raster file containing elevation values. This file contains 100 foot pixels and the vertical units for the pixel values are feet.
cherokee_landsat_backdrop_natural_color_subset.img – The natural color bands of a Landsat image. Assign red/green/blue to bands 1/2/3 for viewing. This image is not used by the helicopter landing zone model but is useful for a backdrop image when viewing the model results.