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Calculating Surface Area

Updated May 19, 2016

This article applies to:
  • Terrain 3D
  • Terrain Forestry
  • RoadEng Civil
  • RoadEng Forestry

Download the example files here: Calculating Surface Area

Polygon Surface Properties (Surface Area, Volume, Average Slope and Aspect) Example

In this example we will demonstrate how to calculate the surface properties such as area, enclosed volume, average slope, and aspect. To do this we will superimpose a 2D polygonal feature on a TIN model. By setting the polygon to be a “Surf./Vol. Boundary”. This will cause the surface properties (surface area, average slope, average slope dir.) to be calculated during the Volume Surface Properties calculation.

  • Start the Terrain program and open file Sarea2.ter (included with this example).
  • Select the polygon feature with the mouse. Choose menu Edit | Modify Selected Features | Properties. Select properties (Displayed, Connected, Modelled and Surf/Vol. Boundary). Press OK.
  • Choose menu Edit | Terrain Modelling | the Calculate Volume Surface Properties. Make sure Volume enclosed by a single surface is selected. Press OK.

Figure 1 – Terrain File Sarea2.ter

Sarea2.ter contains contours and a polygon feature (dashed line). We will calculate the surface properties of this polygon.

The Surf/Vol Boundary Property is of prime interest in this example. With this set the surface properties will be calculated.

Figure 2 – Edit | Modify Selected Feature(s) | Properties

Figure 3 – Terrain Calculation Dialog Box.

When the calculation is complete, the Volume / Surf. Properties dialog will appear. As shown below. Note that in addition to feature-1, a new feature has been added to the file (TIN~-0). This feature surrounds the entire TIN model. It’s properties have also been calculated.

Figure 4 Volume / Surf. Properties Dialog Showing Surface Properties