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

Field Survey Technques - Cross Sections

The levels for the defining of the sections may be obtained by one of the following methods;

• conventional levelling
• tacheometric methods
• interpretation from digital terrain models.

A cross section of the natural surface indicates the existing ground profile normal to a fixed direction at a selected point. The fixed direction is usually of significance such as the centreline of a road or river. Cross sections may be taken at right angles to this direction at a constant interval. Along the cross section levels are measured at points, usually separated by a fixed distance. The use of fixed distances between and along cross sections is a convenient method to collect the data (greatly reduces the amount of field to office computations) but has one significant disadvantage. Because the distances are fixed it is not possible to collect the data at locations that best define the terrain; this drawback will be discussed further under the section on digital terrain models.

The typical cross sections shown above may therefore be repeated at regular intervals; the hatched areas of each cross section may be calculated (say by Simpson's Rule) and by summing each individual area the total volume may be determined. It is normal to draw the cross sections with differing horizontal and vertical scales; while this is an advantage in graphical representation it can create difficulties when areas are to be computed directly from the drawing. Beware of these differences! It is also assumed at this stage that the centre lines, along which the cross sections are taken, are straight. In the more general case this is not a necessary assumption with the result that the simple formulae developed here are no longer valid.