101 Contour

from
ISOM 2017-2

Geometry: line.

Definition

A line joining points of equal height. The standard vertical interval between contours is 5 m. A contour interval of 2.5 m may be used for flat terrains. Slope lines may be drawn on the lower side of a contour line to clarify the direction of slope. When used, they should be placed in re-entrants. A closed contour represents a knoll or a depression. A depression has to have at least one slope line. Minimum height/depth should be 1 m.

Relationships between adjacent contour lines are important. Adjacent contour lines show form and structure. Small details on contours should be avoided because they tend to hide the main features of the terrain. Prominent features such as depressions, re-entrants, spurs, earth banks and terraces may have to be exaggerated.

Absolute height accuracy is of little importance, but the relative height difference between neighbouring features should be represented on the map as accurately as possible. It is permissible to alter the height of a contour slightly if this improves the representation of a feature. This deviation should not exceed 25% of the contour interval, and attention must be paid to neighbouring features.

Contours shall be adapted or broken in order not to touch symbol Small knoll (109) or Small elongated knoll (110).

Parameters

The smallest bend in a contour line is 0.25mm from centre to centre of the line (footprint 4 m). The mouth of a re-entrant or a spur must be wider than 0.5 mm from centre to centre of the line (footprint 8 m).

The minimum length of a contour knoll is 0.9 mm (footprint 13.5 m) and the minimum width is 0.6 mm (footprint 9 m) outside measure. Smaller prominent knolls can be represented using symbol Small knoll (109) or Small elongated knoll (110) or they can be exaggerated on the map to satisfy the minimum dimension.

A depression must accommodate a slope line, so the minimum length is 1.1 mm (footprint 16.5 m) and the minimum width is 0.7 mm (footprint 10.5 m) outside measure. Smaller, prominent depressions can be represented using symbol Small depression (111) or they can be exaggerated to satisfy the minimum dimension.

Colour: brown.