Wikipedia:Categorization of location

The Wikiproject Geographical coordinates is busy tagging all articles about locations on Earth with their geographic coordinates using the  family of tags; this gives readers access to maps and aerial photography and allows external sites to create mashups showing Wikipedia articles on maps. Right now, it is not possible to access a list of articles about nearby locations from a given Wikipedia article. The Location Categorization Project is designed to remedy this.

For every region of size 1° latitude by 1° longitude, a Wikipedia category is created; for example Category:Locations 37°N 122°W to 38°N 123°W. Twenty-five of these are grouped together in a larger category of size 5° by 5°: Category:Locations 35°N 120°W to 40°N 125°W, and 36 of those make up a toplevel category of size 30° by 30°: Category:Locations 30°N 120°W to 60°N 150°W. There are thus 72 toplevel categories.

Every article about a location or area is placed in at least one of these categories, namely in the lowest-level category that contains a majority of the area. So if the described location or area covers only a few 1° by 1° regions (such as a city for example), then it is placed in those 1° by 1° categories that capture a major portion of the area; if it is significantly larger (such as a U.S. state) then it is placed in the corresponding higher level categories that capture major portions of it. Many countries will be placed in the top-level categories, and all of these belong to Category:Locations.

Every locations category page will contain links to the neighboring location categories at the same level, a  link for the center of the region using the right scale so that maps and aerial photography are readily accessible, and a short one-sentence description of the location categorization system.

(To quickly find the extend of regions in terms of geographic coordinates, Google Earth's View/Grid (Control-L) feature is very useful.)

Design decisions

 * All categories at the same level were chosen to be of the same dimension in terms of degrees; because of the nature of the coordinate system used, this implies that the categories won't all have the same size. Trying to use equally-sized categories would be overly complicated without much benefit.
 * The number of categories at each level was chosen so that there's a manageable number of subcategories: 25-36.
 * The system is extensible in a flexible manner: for certain urban areas, it is probably desirable to create a grid of 10' by 10' location categories. Not all 1° by 1° categories have to be broken up that way.
 * We use "Locations 10°S 20°E to 15°S 25°E" instead of "Locations 15°S 20°E to 10°S 25°E". The latter scheme would have been slightly more pleasing mathematically (always using the South-West corner first and the North-East corner second, which the adopted scheme does not do), but it would probably be too confusing to most readers.
 * Every category has four neighbors at the same level, which is nice and manageable, except for the North and South pole, where all hell breaks loose because the coordinate system has singularities there. Trying to remedy this seems to create more problems than it solves.
 * An article about an area is placed only in the category or categories that captures a major portion of its area. An alternative would have been to place such an article into all the categories touched by the area. The latter would create undesired effects if the area only covers a minor part of neighboring cells.

Update
The location categories were deleted; the discussion leading up to this decision can be found here.