Distortion (cartography)

Classic Mercator projection: Greenland appears as large as Africa in terms of area, although it is actually 14 times smaller; also that the Antarctic is depicted as large as the rest of the land area does not correspond to reality.

As a distortion in which is mapping the change of distances , angles or surface dimensions indicated by the projection of the globe onto the (planar) surface of the map occurs. Such distortions are inevitable when depicting any surface curved in two directions; on the other hand, a distortion-free representation is only possible with developable surfaces (plane, cylinder, cone), i.e. H. for surfaces that are only curved in one direction or not in any direction .

The distortions are generally stronger, the larger the represented area of ​​the earth's surface (or on the moon, planet, starry sky ) is. Therefore, when placing adjacent map sheets together, certain gaps occur at the edges.

The type of distortion depends on the map projection :

• General route accuracy is impossible, but route distortion in certain directions can be avoided or kept low.
• Conformal projections distort surfaces particularly strongly (example: the Mercator projection , in which Greenland with 2.17 million km² appears as large as Africa with 30.2 million km²).
• Equal area projections distort angles particularly badly (examples: azimuthal equal area and gnomonic projection ).

See also

• Tissot indicatrix