Cross-Section Cubature: A Practical Guide
For roads, canals and channels, engineers rarely compute earthwork as a single blob of volume. They use cross-sections. This guide explains cubature — the station-by-station method behind most earthwork quantity tables.
Sections along an alignment
Cubature works by cutting cross-sections at regular stations along a centreline or axis. At each section, the cut area and fill area between the existing ground and the design are measured.
Because the sections are evenly spaced, the method produces a clean, checkable table of quantities rather than one opaque number.
From areas to volume
The volume between two neighbouring sections is estimated from their areas and the distance between them — most commonly with the average end-area method, which averages the two section areas and multiplies by the spacing.
Summing these along the alignment gives the total cut and fill.
Why engineers still prefer it
Cubature is transparent and auditable. Anyone can open the station table, check a section, and trace the total. It also produces the section drawings that go straight into a set of construction plans.
Cutting the sections directly from a DEM keeps the ground line honest, so the quantities match the real terrain.
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