# Compute volume

You can calculate volumes from surfaces stored in triangulated terrain model (TTM) files.

You can import TTM files from your office software or generate them from the map in General Survey. See Creating a surface from existing points.

1. Tap and select Cogo / Compute volume.

   Alternatively, to create a surface at the same as time as computing a volume. select at least three 3D points in the map and then from the tap and hold menu, select Compute volume. Enter the name for the surface and tap Accept. The surface appears in the map.

2. In the Compute volume screen, select the required calculation method:

   - Above an elevation method

     Calculates the volume of a single surface above the specified elevation. Only the cut volume is computed.

   - Void volume method

     Calculates the volume of material needed to fill a surface up to the specified elevation.

   - Surface to elevation method

     Calculates the cut and fill volumes between a single surface and the specified elevation. Where the surface is below the elevation, fill will be computed; where the surface is above the elevation, cut will be computed.

   - Surface to surface method

     Calculates the cut and fill volumes between two surfaces. The Initial surface, is the original surface and Final surface is the design surface or surface after excavation. Where the Initial surface is above the Final surface, then cut is computed; where the Initial surface is below the Final surface, then fill is computed.

     Volumes are computed only in areas where the initial and final surfaces overlap.

   - Stockpile/depression method

     This works in a similar way to Surface to surface except with only one surface. The selected surface is treated as the final surface and the initial surface is defined from the perimeter points of the selected surface. Where the surface is above the perimeter surface, then cut is computed (stockpile); where the surface falls below the perimeter surface, then fill is computed (depression).

   - Surface area method

     Calculates the surface area, and using the specified depth can calculate the volume.

3. Select the surface to use.

4. If required, enter the Haul bulkage or Shrinkage factor to apply to the calculation.

   A haul bulkage factor allows for the expansion of cut material as it is excavated. Haul bulkage is defined as a percentage. The Adjusted cut volume is the cut volume with the haul bulkage factor applied to it.

   A shrinkage factor allows for compaction in fill material. Shrinkage is defined as a percentage. The Adjusted fill volume is the fill volume with the shrinkage factor applied to it.

5. Tap Calc.

   After haul bulkage and/or shrinkage have been applied, the software shows the In situ volume (original volume) and the Adjusted volume:

   - The Adjusted cut volume is the cut volume with the haul bulkage factor applied to it.
   - The Adjusted fill volume is the fill volume with the shrinkage factor applied to it.