(1) The intersection of a solid with a developable surface (usually a plane). For example, a vertical section of the ground or of underlying strata. A cross section, in this sense, should not be confused with a profile, which is the intersection of a surface with a developable surfaced. (2) The trace, in a vertical plane perpendicular to a given, horizontal line or route, of the terrain through which the plane passes. (3) A horizontal grid laid out on the ground for determining contours, quantities of earthwork, etc. , using the elevations of the intersections of the grid. (4) A section taken perpendicularly to the centre line of a proposed construction such as a road, canal or dam.