Zoomniveau

Zoomniveau is a term used to describe the level of magnification or level of detail of a map, image, or user interface. In map applications and geographic information systems, zoomniveau is typically an integer that increases as the view becomes more detailed and smaller in area. Higher zoomniveaus show finer detail, while lower ones cover a larger area with less detail.

In tile-based maps, zoomniveau operates as a tile pyramid. At each step up in zoomniveau, the map is rendered with twice the linear resolution, and a tile cache contains more tiles. Most web maps use tiles of 256 by 256 pixels, and the world is represented with 2^z tiles on each axis at zoomniveau z, meaning there are 4^z tiles in total at that level. When a user pans or zooms, the client requests the tiles corresponding to the active zoomniveau and viewport.

The relationship between zoomniveau, projection, and scale depends on the mapping system. In Web Mercator (EPSG:3857), commonly used by web maps, the ground resolution roughly halves with each increment of zoomniveau, while the displayed scale depends also on screen pixel density. This means that a higher zoomniveau provides more detail but covers a smaller geographic area per pixel.

Common values vary by platform: Google Maps typically uses zoomniveaus 0 to about 21 or 22; OpenStreetMap uses roughly 0 to 19; Bing Maps uses up to about 21. Besides tiled web maps, the term can also describe magnification in raster images or scanned documents, where zoomniveau functions similarly as a discrete level of magnification.

In summary, zoomniveau encapsulates how much of a map or image is shown and at what level of detail, with a consistent, discrete structure in tiled mapping contexts.

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