Karttaprojektiojärjestelmä

Karttaprojektiojärjestelmä refers to the method used to represent the three-dimensional surface of the Earth or a portion of it on a two-dimensional plane, such as a map. Since the Earth is approximately spherical, a perfect, distortion-free representation on a flat surface is impossible. Karttaprojektiojärjestelmät involve mathematical transformations that inevitably introduce some form of distortion, affecting either shape, area, distance, or direction.

Various projection systems exist, each designed to minimize certain types of distortion at the expense of others, depending on the intended use of the map. Common types include cylindrical projections (like Mercator), conic projections, and azimuthal projections. For example, the Mercator projection preserves local shapes and angles, making it useful for navigation, but it significantly distorts areas near the poles, making them appear much larger than they are.

In practical applications, especially in geographic information systems (GIS) and surveying, specific coordinate reference systems are employed. These systems define not only the projection method but also the datum, which is a reference model of the Earth's shape and size. Examples of widely used coordinate reference systems include Universal Transverse Mercator (UTM) and various national grid systems. The choice of a particular karttaprojektiojärjestelmä is crucial for accurate spatial analysis and representation of geographic data.