Applicable plans

Valley Mountain Peak

You have collected survey data at two **different time steps** and you want to calculate the **volume difference **between both surveys.

**Principle**

To calculate a volume difference you need to perform 2 steps:

**Step 1:**Calculate the volumes using the data from each survey (at an arbitrary level).

**Step 2:**Calculate the difference between the obtained values.

**Note:**This technique provides you with a total cut or fill value for the specified area. The spatial distribution of the materials within the polygons is not taken into account.

**Quick guide**

- Open the terrain created using the data from the 1st survey.
- Then add the 2nd survey to this project. Go to the Insert tab > Terrain and click the Elevation button.
- Select the elevation terrain created using the data from the 2nd survey.
- Click Open and the elevation terrain will be added to your project. Hence, you will have the elevation data from both time steps loaded in one project.
- Draw the polygons around the stockpiles you want to use in the volume calculations (Home > Drawing > Polygon).
- Go to the Home tab > Volume Operations and set the Reference to Flat.
- Set the Elevation value in a way that assures that your Reference plane does not intersect any of the stockpiles, e.g., 0,00 m.
- Calculate the volumes of the stockpiles (Home > Volume Operations > Calculate Volume). Since the elevation layer from the 2nd survey is enabled, these are the volumes from the 2nd survey.
- Uncheck the elevation terrain in the ProjectTree. The elevation of the first survey will become active.
- Calculate the volumes again using the same arbitrary Reference level. These are the volumes from the 1st survey.
- Export your volume information. Both volume calculations will be exported.
- Calculate the volume difference using the data you exported. This can be done, for example, in Excel.