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Volumes
Cross Sections
End Area Method
Prismoidal Formula
Rectangular Base Method
Triangular Base Method
Balance of Cut and Fill
Volumes From Contours
Digital Terrain Models
Volumes From Contours
The method used is simply the end area method or the prismoidal formula, the cross section being replaced by the areas contained within successive contours (see below). The distance between sections, or in this case contours, simply becomes the contour interval. As the contained areas are usually quite irregular they are normally determined by planimeter or by computers and digitising software. The process is laborious and is becoming less popular with the advent of digital data and digital maps. The volume of the hill shown below is,
| V = c | [a1 + 2a2 + 2a3 + a4] | where c in the contour interval. |
| 2 |
The formula ignores the volume of the apex of the hill top; this could be included by making a5 = 0 or by the additional use of some other suitable method.
