In this exercise, you will calculate volumes by the grid volumes method. The grid volumes method works by superimposing a grid on both surfaces in the stratum, extracting elevations at grid line intersections, and then compiling the difference in elevation at each concurrent grid line intersection.

1. On the Terrain menu, click Grid Volumes Calculate Total Site Volume to display the Site Librarian dialog box.

2. From the Select site list, select Site1, and then click OK to display the Grid Volume Settings dialog box.

3. Accept the default values in this dialog box by clicking OK and displaying the Volume Results Surface dialog box.

4. Enter G1-Site1 for the New surface, and then click OK.

   If you are working with several sites and strata it is helpful to develop a naming convention for the volume surfaces. This aids in correlating a surface to the volumes calculation method used to create it. You can also specify the site name as the surface description in the Terrain Model Explorer when creating surfaces.

   The grid volumes method calculations are displayed on the command line, with a cut volume of 3,376 m3, and fill volume of 20,380 m3, and a net volume of 17,004 m3 of fill.

   Use the following steps to turn on the boundary of the fg surface then generate a Quick View of the new volume surface.

5. On the View menu, click Named Views to display the View dialog box. Under Name, select 2, click Set Current, and then click OK.

6. Click the Layers icon in the toolbar to display the Layer Properties Manager. Turn on the display of the Fg-srf-bdr layer to view the FG surface boundary polyline, and click OK to close the Layer Properties Manager.

7. On the Terrain menu, click Set Current Surface to display the Select Surface dialog box and select Volume Surface. Select G1-Site1 from the list of surfaces and then click OK.

8. On the Terrain menu, click Surface Display Quick View.

Click here to see an illustration of the grid volumes surface quick view.

The area between the fg surface boundary and the extent of the grid volume surface is excluded from the volumes calculations.

Grid squares that fall partially outside of the finished ground surface are ignored when volumes are calculated. This may be avoided by using two surfaces with concurrent boundaries, or by pasting the proposed ground surface onto the existing ground surface. As an alternative, specifying a smaller M and N grid size results in minimizing the impact of grid squares occurring outside of the finished ground surface.