Slope Zone Analysis

Function

This command calculates the surface area of a site in different slope zone ranges. This command can use either a surface model file, (.TIN, .GRD, or .FLT), or 3D Face drawing entities, which can be generated by the Plot 3D Grid File command, the Draw Triangular Mesh command, or the Draw Triangulation Faces option of Triangulate & Contour.  For each slope zone, the 3D Faces can be hatched with any AutoCAD hatch pattern, including the SOLID pattern, or left empty with the NONE pattern.

This command can also generate contours of the slope zones based on the calculated slope at each point of the 3D Faces. The slopes can vary greatly between neighboring points. When contoured directly, these slope data points produce incoherent contours. Instead this routine applies a filtering algorithm that reduces the noise. There is another option to output a grid file of the slope values.

There are also options to specify inclusion and exclusion areas. When inclusion areas are specified, only the slope area within the inclusion polyline is calculated. Slope area within an exclusion polyline are not included in the calculations. Inclusion and exclusion areas are represented by closed polylines and must be drawn prior to calling this routine. Without inclusion and exclusion polylines, all the slope area of each selected 3D Face is used.

Prompts

Source of surface model: [File/<Screen>]? F for File
Slope Zone Options dialog box.  Choose whether to Draw Slope Zone Contours, whether to Output Grid File of Slope, and Slope Format.  Pick OK.
Select surface model file.
Define Ranges dialog.  Specify the slope zones, colors and patterns from lowest to highest.  Pick OK.
Select the Inclusion perimeter polylines or ENTER for none:
Select the Exclusion perimeter polylines or ENTER for none:
Report is generated.

If you choose to draw Slope Zone Contours, the Contour Options dialog box is presented.

Note: If you choose to use Screen entities instead of a surface model file, you are prompted whether to:
Apply hatch patterns to grid cells [Yes/<No>]? and
Freeze grid layer after processing [Yes/<No>]?

Surface contours

3D Faces from a grid surface model

3D Faces created by Triangulate & Contour with the Draw Triangulation Faces option

Slope zone contours

Slope zones that follow the surface contours using the triangulation 3D Faces

Pulldown Menu Location: Surface > Slope Analysis
Keyboard Command: szone
Prerequisite: Surface model file (.TIN, .GRD, or .FLT), or 3D Faces entities
File Names: \lsp\elanal.lsp, \lsp\contour4.arx