Wikipedia:WikiProject Geographical coordinates

WikiProject Geographical coordinates aims to better organize location information in articles containing a set of numbers that identifies location on and relative to the Earth. In particular, we aim to establish a standard for uniform handling of latitude and longitude coordinates as given in various Wikipedia articles, somewhat analogous to how ISBN numbers are handled.

NOTE: This is a concept currently under development, so this is subject to change.



Related WikiProjects
WikiProject Council includes this WikiProject in its Geographical directory. This WikiProject is an offshoot of WikiProject Maps:


 * WikiProject Geography
 * WikiProject Maps
 * WikiProject Geographical coordinates

...and is the parent project of:


 * Wikipedia-World

Other WikiProjects that make use of geographical coordinates include:


 * Meta:Category:Wikimaps
 * WikiProject Cities
 * WikiProject Countries
 * WikiProject Glaciers
 * WikiProject Lakes
 * WikiProject Microformats Geo
 * WikiProject Mountains
 * WikiProject OpenStreetMap
 * WikiProject Protected areas
 * WikiProject Rivers
 * WikiProject U.S. counties
 * WikiProject United States

Associated Portals
The AtlasPortal is associated with WikiProject Geography.

The Geography Portal is associated with WikiProject Geography.

Participants
This list has been moved to its own page.

Goals

 * 1) Undcstrmrc.png Should provide a uniform markup for all geographic coordinates
 * 2) Undcstrmrc.png Should provide a user-preferred appearance for all geographic coordinates
 * 3) Greentree.jpg Markup should be easy and natural to use
 * 4) Check mark.svg Undcstrmrc.png Should be able to have a uniform, extensible way of accessing all types of map resources, avoiding having direct external links to maps in articles
 * 5) Check mark.svg Clicking on a reference navigates directly to a page with external pointers to various resources, with coordinates automatically embedded where possible. The resources can be maps of various kinds, topological charts, satellite photos and others.
 * 6) Check mark.svg Create a database of points, enabling generation of navigatable maps with a clickable icon appearing for every location for which there is a Wikipedia article. This has been implemented for NASA World Wind, Google Earth (see below) and Google maps (see below).
 * 7) Check mark.svg Serve as a tool for finding Wikipedia articles describing nearby locations. See also Wikipediatlas.
 * 8) Question dropshade.png Adhere to existing Internet standards for geographic coordinates as far as possible such as using WGS84 for terrestrial coordinates

Usage guidelines

 * See also MOS:COORDS

In general, coordinates should be added to any article about a location, structure, or geographic feature that is more or less fixed in one place. Such items can vary in size from a single tree (or smaller) to entire oceans or continents. Coordinates should also be added to articles about events that are associated with a single location, for example, the Ufa train disaster. Guidelines for less obvious situations are given below.

Coordinates are appropriate for the top articles or within infoboxes of the following types of articles:
 * Businesses/organizations with a single location (even if they are defunct)
 * Demolished buildings/structures
 * Buildings/structures that have been proposed, but not yet built (if there is a reliable source for the location)
 * Permanently docked ships (and shipwrecks)

Do not add coordinates to the following types of articles:
 * Biographies of living people
 * Works of art (other than permanent outdoor statues, installations or murals)
 * Sports teams (add to the stadium article instead)
 * Businesses with multiple locations (although listing coords for individual locations in a table may be appropriate)
 * Ships that are not permanently docked or sunk

Other types of articles may be decided on a case-by-case basis.

Which coordinates to use
National mapping agencies such as the Geographic Names Information System (GNIS), Ordnance Survey (OS), and Geographical Names Board of Canada (GNBC) are usually reliable sources for coordinates. The GEOnet Names Server (GNS) database is not reliable. Always double check the coordinates on an internet mapping service. For other locations, the following points should be considered:
 * For villages, towns, communities, etc., use the current centre. Where this is difficult, choose the earliest known settlement of that name. Be aware that the GNIS coordinates may be an arbitrarily chosen civic feature, as that was the usual rule.
 * For military and industrial establishments (e.g., castles, barracks, dockyards, car plants) use the main gate.
 * For administrative districts, use the head office.
 * For geographical features with an area, such as lakes, reservoirs, and islands, use a point reasonably in the center of the feature. (Remember not to specify too much precision; see Precision guidelines below.)
 * For linear features, see WikiProject Geographical coordinates/Linear. Be aware that the GNIS primary coordinates will usually be of the feature "mouth" and thus may differ.

Markup
The practical usage of coordinate markup in Wikipedia is described in the style guide for geographical coordinates. For use on maps and other services, parameters may also be required.

A complete entry could for example be:

See also: Obtaining coordinates

Marking project-related pages on Talk page
The template   may be added to relevant Talk pages. This adds the page to several categories and displays as:

Coordinate templates
There are two ways of specifying coordinates:


 * 1)  – Accepts multiple data formats and supports a style sheet preference for display format, plus a Geo microformat.   may be placed anywhere in the article source text, inline, with prose text. For example " ", which displays as "Mount Everest is at 27.98778°N, 86.94444°W". To display coordinates at the page's top, near the article's title, in a skin-dependent way, use   (see example at Krasnoyarsk hydroelectric dam). To display both inline and top, use.
 * 2) Infoboxes – Many infobox templates for places have a parameter, typically coordinates, for specifying a place's coordinates. The template internally uses coord and may therefore also display in the title area. See Template:Infobox Settlement and Template:Infobox Mountain for documentation, or, usage examples at Los Angeles and Mount Everest.

(Before September 2008, there was a widely-used family of templates of the form coor .... These are deprecated and have been replaced by coord. For an overview of choices: WikiProject Geographical coordinates/comparison.)

Parameters
Following the geographical coordinate, further parameters can optionally be supplied, separated by underscores. This helps display suitable map resources (see Template:GeoTemplate), and will help Wikimaps become fully functional.

For example:
 * displays 61.1631°N, -149.9721°W

It has
 * type:landmark
 * globe:earth
 * region:US-AK
 * scale:150000
 * source:gnis

Name
coord takes

If an article contains several display=inline coordinates, each of these may be supplied with a unique name. This name will be used to display the coordinate on the WikiMiniAtlas, and will cause the template to emit an hCard microformat using that name, even if used within an existing hCard. Do not use when the name is that of a person (e.g for a gravesite), as the generated hCard would be invalid. Also, do not use square brackets in names.

Format

 * will reformat the coordinates to decimal degrees for all readers.
 * will reformat the coordinates to degrees | minutes | seconds (dms) format for all readers.

Creating new templates
When creating new templates or infoboxes, use coord. Unless a template uses the coordinate data in another way, the coord template should be the field value. For example, infobox lake accepts.

If coordinate data are used directly by a template, use the following parameter names for coordinates:

A provision for accepting decimal coordinates is recommended. For example, allow  and omission of the remaining parameters.

Where the United Kingdom's Ordnance Survey grid references are used as the coordinates, use.

For articles which have no coordinates, but need them, use.

Linear features
For draft guidance on, and examples of, coordinates for linear features (rivers, roads, bridges, tunnels, etc.), see WikiProject Geographical coordinates/Linear.

How to obtain geographical coordinates
See Obtaining geographic coordinates

See also: Category:Articles needing coordinates, Maybe-Checker

Geodetic system
All coordinates specified through coord must be referenced to WGS84, or an equivalent datum. WGS84 is required for some of the conversions done by the geohack extension.

British national grid references of the Ordnance Survey use its own OSGB36 datum, which is correct for use in national grid references; the correct transformations will automatically be applied when national grid coordinates are used in oscoor tags. However, OSGB36 latitude/longitude coordinates should not be used anywhere in Wikipedia; please use WGS84 lat/long instead.

Precision guidelines
Regardless of how coordinates are obtained, consider the precision specified in a Wikipedia article. Reliable secondary sources exist for some locations. Without a reliable source, the larger the object being mapped, the less precise the coordinates need to be. Cities must be specified with a precision of degrees, minutes and seconds to respect historical norms. When the guideline is used, degrees, minutes and seconds or d.dddd are the default. To specify a particular point in the city, such as a building, generally requires precision down to degrees-minutes-seconds or d.dddd° if decimal degrees are used. In the case of objects such as fountains or statues, it may be necessary to use d°m's.s" or d.ddddd°. Higher precisions should be avoided, as they greatly exceed the accuracy of civilian GPS and online mapping services. (Using 4 m accuracy as an estimate for civilian GPS: Depending on the coordinates format and the latitude, the next-higher precisions exceed the accuracy by a factor of somewhere between 13 and 72.)

A general rule is to give precisions approximately one-tenth the size of the object, unless there is a clear reason for additional precision. Overly precise coordinates can be misleading by implying that the object is smaller than it truly is.

There is no set way to determine object size, and the boundaries of many geographical objects are not clearly defined or not readily available. The difference rarely affects the suggested coordinates precision, so a rough size estimate is usually adequate. However, it should be noted that object size is always linear (one-dimensional), not an area measurement.

In the two most-used coordinate representations, degrees-minutes-seconds and decimal degrees, precision is, as a useful approximation,

Conversions: 1 km, 1 m, 1 cm; 1 mi, 1 ft, 1 in

The values in the table give distances in the east-west direction corresponding to a small change in longitude, at different latitudes. You can take the equator columns of the table as a rough guide to distances in the north-south direction that correspond to a small change in latitude, since they vary only a little bit at different latitudes. For simplicity, however, the latitude precision is commonly copied from that of the longitude.

Precision tables
The following tables show suggested coordinates precisions for various object sizes and latitudes. Refer to the preceding section for more information about coordinates precision. To use these tables:
 * Choose one of the tables depending on whether you want degrees-minutes-seconds format or decimal degrees format
 * Find the column that is closest to the latitude of your object
 * Find the row that is closest to the size of your object
 * Note the coordinates precision at the intersection of your row and column

Example: You want coordinates, in decimal degrees format, for Yosemite National Park, California, U.S. To solve: (This is a good example of a borderline case, as the latitude is quite close to 37.5°, the midpoint between 30° and 45°. If the Park were a mere 25 miles to the south, you would use the 30° column instead, yielding a different precision: d.dd°. You could opt for that precision instead, giving 37.85, −119.56. That's your call. But the table shows that more than two decimal positions would definitely be too precise for this case.)
 * The size of the object is roughly 70 km
 * GNIS query gives the Park's location, in decimal degrees, as: 37.8483188 (north latitude), −119.5571434 (west longitude)
 * Choose the Decimal degrees format table
 * Find the 45° column; 37.8483188 is (slightly) closer to 45° than to 30°
 * Find the 50 km row; 70 km is closer to 50 km than to 100 km
 * Note the precision at the intersection of row and column: d.d°
 * Round to the selected precision: 37.8, −119.6


 * 1) The tables are derived from the precision data at, above. As suggested there, they use a target resolution of one-tenth of the object size.
 * 2) The tables are not perfect. Some cases will yield a precision that is different from what you would get by doing the math (including trigonometry) for that specific case. This is because it is impossible to represent all cases correctly in a usable tabular format. The tables provide the correct precision for a majority of cases. Any error should be limited to one level of precision (e.g., d° m' vs. d° m' s", or d.ddd° vs. d.dddd°), which is acceptable for the purposes of Wikipedia coordinates.
 * 3) d.ddddd° is roughly three times more precise than d° m' s.s".

Mathematical formulas
You can also calculate the kilometers per degree of longitude, k, using one of the following formulas (θ is the latitude, 6378.14 km is the equatorial radius, and 6356.8 km is the polar radius):

Accurate, assuming a spheroid:
 * $$k = \frac{\pi}{180}\cos(\theta)\sqrt{\frac{(6378.14^2\cos\theta)^2+(6356.8^2\sin\theta)^2}{(6378.14\cos\theta)^2+(6356.8\sin\theta)^2}}$$

Approximate:
 * $$k = 111.3\cos\theta\,$$ Equator to latitude 25° (north or south)
 * $$k = 111.2\cos\theta\,$$ Latitude 30° to 40°
 * $$k = 111.1\cos\theta\,$$ Latitude 45° to pole

Tools and applications based on coordinates from Wikipedia
Articles (and coordinates) can be found through the pages using the templates in Category:Coordinates templates

All coordinates are available for download in Wikipedia database dumps. To get the coordinates from the XML format dump of all articles (enwiki-latest-pages-articles.xml.bz2, 4 GB), the dump needs to be parsed for pages containing coordinates in the entry formats listed above. Most articles in Wikipedia conform to these formats and coordinates are easy to parse from the wikitext with regular expressions for simple character sequences. As all coordinates link to the same PHP tool, they may also be found from the SQL format table of external links (enwiki-latest-externallinks.sql.gz, 725MB). This second method will however not include all available information about the coordinates, such as their position between the article body and the title area.

There may exist some groups of articles that generate the coordinate data dynamically and are not in any of the standard entry formats, as some editors may have wished to facilitate entry of common coordinate related information, while only keeping the output similar with the existing templates. To get all such coordinates, all the articles in the database dump need to be run through a wikitext parser (such as the PHP one in MediaWiki) to expand all the templates, and the result parsed for coordinates. Alternatively, it is also possible to download the HTML generated from all the article and expanded template content (wikipedia-en-html.tar.7z, 14 GB).

Note that mass downloading individual pages from the live Wikipedia site is strongly discouraged and may lead to discontinued access.

NASA World Wind Samples
All examples use NASA World Wind, with the Wikipedia overlay. This is purely meant as an example of using a coordinated concept for geographical coordinates.

View Wikipedia in Google Earth
Project Wikipedia-World scan 11 Dumps (ca,cs,de,en,eo,es,fi,fr,nl,pt,ru) and provides:
 * dynamic Google-Earth layers in 21 languages. For instance: english Layer, español Layer
 * static Google-Earth layers in 10 language with different folders (Castles, Parks,...), Download at webkuehn.de
 * SQL-Data of all scanned coordinates

Copernix.io - View and search Wikipedia Articles on a map
Copernix.io is a geographical search engine allowing users to search places and information from Wikipedia on a map. Users can leave the search bar empty to see all pages within an area or type a query to get subject specific information.

Some useful examples can be found at: The main search page is at:
 * Copernix examples and about
 * Copernix.io

Visualization of Wikipedia articles with Google Maps

 * www.geonames.org over 800,000 Wikipedia articles in 230 languages on Google maps. The placemarks include short descriptions of the displayed items, extracted from the Wikipedia articles. Webservices for full text search and reverse geocoding of Wikipedia articles.

WikiMiniAtlas JavaScript plugin
WikiMiniAtlas is a JavaScript to add to your monobook.js. It adds a draggable and zoomable (just like GoogleMaps) map to all geo-coded articles. Clickable labels with links to other geocoded articles are placed on the map to allow spatial browsing of Wikipedia. Map layers include satellite images (using Landsat7 data) with zoomlevels down to a resolution <100m, and daily updated MODIS satellite data.

WikiMiniAtlas is currently enabled on Wikipedia (by clicking on the globe beside the coordinates).

All geodata in SQL file format

 * Project Wikipedia-World, provides the complete database for download in SQL-file format.

Export multiple coordinates
Kmlexport tool: Pages marked with multiple coordinates or categories of articles with coordinates can be exported as KML (for use in Google Earth, for example). This tool and some alternatives can be found on clicking the coordinates or by applying the GeoGroup template on a page.

The Kmlexport can be used directly or through Google Maps; see for example Colmar Pocket or Category:Capitals in Europe. Export from articles is real-time, export from categories is based on stored extractions (may be several weeks old).

KML may be converted in other formats, suitable as Points of Interest (POI) for GPS systems.

Other sources:
 * Wikitude provides coordinates as KML or TomTom POI format.

Coordinates search tool
~dispenser/cgi-bin/geosearch.py allows for regular expression searching on the GeoHack links in the external links table. This has the advantages of near real time information and powerful pattern matching. The following are some example queries created as a demonstration of the flexibility of the system.