Isohypsit

Isohypsit is the Finnish term for contour lines on topographic maps. In English, these lines are usually called contour lines or isohypses and connect points of equal elevation above mean sea level. They form a graphic representation of terrain relief, enabling readers to grasp the shape of the land, slope steepness, and elevation changes.

Contour lines are drawn at regular elevation intervals, known as the contour interval, such as 5, 10, or 20 meters. The interval is chosen based on map scale and terrain: small-scale maps use larger intervals, while rugged terrain may use closer intervals. Index contours, labeled with their elevation, are typically drawn every nth line to aid reading.

In digital mapping and GIS, isohypsit can be generated from digital elevation models; they are used in planning, hydrology, forestry, geology, and outdoor navigation. They can be color-coded or styled to emphasize slope, aspect, or specific elevation ranges. In annotations, steeper slopes appear where lines are closely spaced; flatter areas show wider spacing.

Related terms include isobars and isotherms in meteorology, which are lines of equal atmospheric pressure and equal temperature, respectively. In cartography, contour lines are often referred to as isohypses in some languages, or simply contours.