Sectional Volume Methods


When you compute the materials for a sample line group, you can use three different volume calculation methods: Average End Area, Prismoidal, or Composite.

You can specify which volume method to use in the following dialog boxes:

NoteYou can include multiple corridor baselines in a volume calculation, but you should make sure that the shapes of all sampled corridors are formed accurately. For more information, see Corridor Sections and Sampling Sectional Volumes Across Multiple Baselines.

Average End Area Method

The Average End Area method calculates volumes by adding the area of a material type at one station to the area of the material type at the next station and dividing the sum by two, then multiplying the result by the distance between the sections (L).

Prismoidal Method

The Prismoidal method is similar to the Average End Area method but uses an additional cross section at the middle of the two successive stations.

Composite Method

The Composite method is limited to material lists that have only two surfaces and cannot be used for material lists that contain corridor shapes.

To calculate composite volumes, AutoCAD Civil 3D creates polygons between sample lines and then computes the bounded volumes of those polygons. The polygons are created by joining the offsets of the sample lines between two successive stations, as shown in the following illustration.

The volume is recorded at the second sample line of the polygon. The first sample line in the sample line group will therefore have zero volume associated with it.