Slope Zone Analysis

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), contour polylines, 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 hatch pattern, including the SOLID pattern, or left empty with the NONE pattern. The command reports the area for each slope zone. When using a triangulation surface file, the Save Slope Zone Colors option sets the triangle colors in the TIN file for the slope zones. Then commands like 3D Viewer Surface File can visualize the colored surface. When using the Contours method, the program prompts to select the contour polylines along with optional points to picking up high and low points. Using the Contours method along with the option to Draw Slope Zone Contours with Hatch Slope Zones, the hatch zone boundaries will follow the contours. The Use Report Formatter option allows for customized reports and different output formats.

The Draw Slope Zone Contours option generates contours of the slope zones based on the calculated slope at each point of the 3D Faces. The Output Grid File of Slope option creates 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

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 perimeter(s) or press Enter
Select the Exclusion perimeter polylines or ENTER for none: select perimeter(s) or press Enter
Report is generated.

Slope Report



Surface File: C:\scdev\data\SIMO2.grd

Average Slope: 21.6%

Minimum Slope: 0.0%

Maximum Slope: 81.7%

                Horizontal Surface      Slope Surface           % of    Average

Zone  Range     Area S.F.     Acres     Area S.F.     Acres     Total   Slope %

-------------------------------------------------------------------------------

1                769,137.1     17.657    775,379.4     17.800    51.8      11.8

      20.00%

2                583,761.4     13.401    607,257.9     13.941    39.3      28.2

      40.00%

3                113,978.1      2.617    125,967.2      2.892     7.7      46.8

      60.00%

4                 18,494.6      0.425     22,407.7      0.514     1.2      68.3

-------------------------------------------------------------------------------

Total          1,485,371.1     34.099  1,531,012.2     35.147

If you choose to draw Slope Zone Contours, the Contour Options dialog box is presented. There are settings for the contour layer and whether to label, smooth and reduce the contours. The Hatch Slope Zones option fills in the slope zone areas with colored hatching. The Filter Data to Smooth Contours option applies a filtering algorithm that reduces the noise. The slopes can vary greatly between neighboring points. When contoured directly, these slope data points can produce incoherent contours with the smoothing.

Note: If you choose to use Screen entities instead of a surface model file, you are prompted whether to:
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

Hatched slope zone contours created from the grid 3D Fac

Pulldown Menu Location: Surface >> Slope Analysis
Keyboard Command: szone
Prerequisite: Surface model file (.TIN, .GRD, or .FLT), or 3D Faces entities