Karttaprojektiojärjestelmät

Karttaprojektiojärjestelmät, often translated as Map Projection Systems, are methods used to represent the spherical surface of the Earth onto a flat two-dimensional map. Since a sphere cannot be perfectly flattened without distortion, all map projections introduce some degree of alteration in shape, area, distance, or direction. The choice of projection system depends on the intended use of the map and the specific distortions that can be tolerated or minimized.

Common types of projections include cylindrical, conical, and azimuthal (or planar) projections. Cylindrical projections, such as the Mercator projection, wrap the globe in a cylinder. They are conformal, meaning they preserve angles and shapes locally, but significantly distort area at higher latitudes. Conical projections, like Lambert Conformal Conic, use a cone tangent to or intersecting the globe. They are often used for mid-latitude regions and preserve area or direction along specific lines. Azimuthal projections, such as stereographic, project the globe onto a flat plane from a point. They are useful for depicting polar regions or hemispheres, preserving distance and direction from a central point.

Different projections are designed to preserve certain properties while distorting others. For example, equal-area (or equivalent) projections maintain the relative sizes of landmasses, crucial for thematic maps showing population density or resource distribution. Conformal projections maintain local shapes and angles, essential for navigation charts. Equidistant projections preserve true distances from one or two central points to all other points on the map. Many modern mapping systems, like UTM (Universal Transverse Mercator) and the Web Mercator used in online mapping services, are specific implementations of these projection principles, often balancing different types of distortions for practical applications. Understanding the projection system used for a map is fundamental to correctly interpreting the spatial relationships depicted.