Prosjeksoner

Prosjeksoner are a cartography concept describing a method of dividing the Earth's surface into zones, with each zone assigned a map projection optimized for the zone's extent. The goal is to reduce distortion in regional mapping by using projection properties tailored to local scale and shape requirements.

The term appears in Scandinavian GIS and cartography literature. The word Prosjeksoner is derived from local language usage for projection planning or zoning. The approach emerged in the late 20th century as an alternative to a single universal projection for large territories, aiming to improve accuracy across regions.

Method: Boundaries between zones are defined by geographic features or administrative lines. Within each zone, a projection chosen to minimize distortion in typical mapping tasks is applied. Borders between zones can produce seams, so some implementations employ transitional mathematics or blending to maintain continuity in coordinate values and displayed features.

Applications: National atlases, cadastral systems, environmental planning, and web mapping services that cover large areas. Prosjeksoner can improve accuracy of area measurements, distance estimates, and shape representation for regional analyses while preserving readability at common scales.

Limitations: Increased data management and coordination across zones, potential inconsistencies at zone borders, and higher complexity in software pipelines for data transformation, storage, and display. Maintenance requires agreement on datum, accuracy standards, and update procedures.

See also: Map projection, Transverse Mercator, Equal-area projection.