Equidistance (cartography)
In cartography, equidistance is the difference in height between two adjacent contour lines . Depending on the slope of the terrain and the scale of the map, different equidistance are used. Typical equidistant distances can be 10, 20, 50 or 100 meters. Usually, however, an attempt is made to use a uniform equidistance on the map sheet, since differences in inclination can then be better perceived.
Alternating equidistance is used when the map image contains both mountainous and flat areas. So that the density of the contour lines is not too high in steep areas and not too low in flat areas, additional contour lines are inserted in flat areas.