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===Horizontal coordinates===
{{cnspan|Horizontal position may be expressed directly in [[geographic coordinates]] ([[latitude]] and [[longitude]]) for global models or in a [[map projection]] [[planar coordinates]] for regional models. The German weather service is using for its global [https://www.dwd.de/EN/research/weatherforecasting/num_modelling/01_num_weather_prediction_modells/icon_description.html ICON model] (icosahedral non-hydrostatic global circulation model) a grid based on a [[Icosahedron|regular icosahedron]]. Basic cells in this grid are triangles instead of the four corner cells in a traditional latitude-longitude grid.
The advantage is that, different from a latitude-longitude cells are everywhere on the globe the same size. Disadvantage is that equations in this non rectangular grid are more complicated.}}
===Vertical coordinates===
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