The volume tool is used to calculate volume of a surface above or below a constant (horizontal) plane at a specific elevation. It can compute the volume between two rasters, or between one raster and a constant Z value. The surface Z values and the XY unit of measure of both the rasters must be same in order to calculate the volume. If the Z unit is specified for the primary raster, BandInfo unit will be ignored, else BandInfo unit will be considered while computing the volume.
The Volume tool can be used to calculate:
- The volume of water in a section of river channel at a particular flood stage.
- The volume between the water table and a mining surface
- The volume between a top surface and the bottom surface.
MapInfo Pro Advanced supports the following volume calculation methods:
- Constant
- Between Rasters
Calculating volume between a raster file and a horizontal plane
The Constant method calculates volume for a feature on a flat surface. In this method you need to specify an imaginary plane and then you can calculate volumes above or below the specified Constant surface value. The Constant method supports the following:
- Above Plane - Computes volume of primary raster above constant Z value.
- Below Plane - Computes volume of primary raster below constant Z value.
Calculating volume between two raster files
The volume between the two rasters is calculated by subtracting each primary raster cell Z value from the corresponding cell Z value in the secondary raster. The value obtained after subtraction is then multiplied by the primary raster cell width (X) and height (Y). This calculation gives us the volume of a single raster cell. Each individual raster cell volume is then added together to compute the final volume.
The Between Rasters method supports the following operations:
- Above Primary Raster - Computes total volume between the primary and secondary raster for areas where the secondary raster's cell value is greater than the corresponding primary raster's cell value.
- Below Primary Raster - Computes total volume between the primary and secondary raster for areas where the secondary raster's cell value is smaller than the corresponding primary raster's cell value.
- Between Rasters - Computes total volume between the two rasters, where they intersect each other. All overlapping cells are considered for the calculation, regardless of which raster is on the top. The difference between cell values is treated as absolute i.e., all values are positive.