Calculating the Volume between Two Surfaces
A common problem solved with a volume calculation is determining the volume of material between two grid files. For example, you might have drill hole data that provides the elevation of the top and bottom of a coal seam, and you want to determine the volume of coal present in the seam. The elevation of the top and bottom of the coal seam defines the upper and lower surfaces, respectively. In this case, the lower surface would be entirely below the upper surface.
To find the volume between two surfaces:
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Create grid files of the upper and lower surfaces. In the example here, the grid files would define the elevation of the top and bottom of the coal seam. Both grids must use the same dimensions and the same number of rows and columns.
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Choose the Grids | Calculate | Volume command and select the upper surface grid file in the Open Grid dialog and then click the Open button.
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In the Grid Volume dialog, the Grid File option button should be selected in the Upper Surface group.
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In the Lower Surface group, click the Grid File option button and click the
button. -
In the Open Grid dialog, select the lower surface grid file and click the Open button.
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In the Grid Volume dialog, verify that the correct grid files are specified for the upper and lower surfaces and click OK. The Grid Volume Report is generated. The volume between the surfaces is reported as the Positive Volume (Cut), which, in this case, is the same as the Volume calculation.
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To save the volume information, use the File | Save As command in the report window and specify a name and file extension. Click OK and the information is saved.