A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although most commonly used to depict geography, maps may represent any space, real or fictional, without regard to context or scale, such as in brain mapping, DNA mapping, or computer network topology mapping. The space being mapped may be two dimensional, such as the surface of the earth, three dimensional, such as the interior of the earth, or even more abstract spaces of any dimension, such as arise in modeling phenomena having many independent variables.
Although the earliest maps known are of the heavens, geographic maps of territory have a very long tradition and exist from ancient times. The word "map" comes from the medieval Latin Mappa mundi, wherein mappa meant napkin or cloth and mundi the world. Thus, "map" became a shortened term referring to a two-dimensional representation of the surface of the world. (Full article...)
A contour line of a function of two variables is a curve along which the function has a constant value. In cartography, a contour line joins points of equal elevation above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness of slopes. The contour interval of a contour map is the difference in elevation between successive contour lines.
Contour lines are curved or straight lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places. Contour lines may be either traced on a visible three-dimensional model of the surface, as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from estimated surface elevations, as when a computer program threads contours through a network of observation points of area centroids. In the latter case, the method of interpolation affects the reliability of individual isolines and their portrayal of slope, pits and peaks.
Erhard Etzlaub, was an astronomer, geodesist, cartographer, instrument maker and physician. From letters from a third party dated 1500 and 1507, we learn that he was a well-known instrument ("compass") maker and a geodesist, and from a letter dated 1517, that "he had also practicised as a physician for at least four years". His death is noted in as the 15th entry in an official list of 20 people buried between December 20, 1531 and February 21, 1532.
On occasion of the Holy Year 1500, when many pilgrims were expected to go to Rome, he designed his famous "Rom-Weg" map, a 41 x 29 cm wood engraving in stereographic projection of app. scale 1:5,6 mio., the earliest printed road map of central Europe. It is, as all of Etzlaub's maps, "South-up". Distances between cities can be computed by dotted lines, where a one-dot-step means one German Mile (7400m). If the prints were coloured, they show political regions, too.