Contour plans
Contour plans are a graphical representation of the lay of the land. They show the degree of slope on a site. They typically relate back to a site datum Datum is a given point that is easily found and recognised from which all other levels or heights can be transferred. referred to as a TBM (temporary benchmark) and may also relate to AHD (Australian height datum). They can be used to determine the extent of cut and fill needed, the height of retaining walls, and the overall finished height of buildings referenced back to natural ground level.
To produce a contour plan a surveyor takes a series of levels over the site at regular grid spacing. These readings are recorded in a surveyor's log book and converted to RLs (reduced levels), which are plotted onto a grid overlaid on the site plan. A draftsperson can then draw lines of best fit between equal RLs. This gives lines that represent each contour interval, eg RL 5.500. Any feature matching this contour will have a level of RL 5.5 m.
You can download a copy of a contour plan (Word 156 KB) for a closer look.