Commons:Geocoding

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On Wikimedia Commons, geocoding is the practice of attaching geographic location information to media. When we geocode media on commons we identify the latitude and longitude from where the media was recorded and attach it to the description page using a {{Location}} or {{Location dec}} template. For jpeg images, geodata can also be stored in the image exif.

Geocoded images on a worldmap

Media which is geocoded can be found in Category:Media with locations.

You can find coordinates for untagged pictures in: Category:Location possible. If you see an image that needs geotags, you can add {{Location possible}}.

Contents

[edit] Geocoding media on commons

Geocoding is easy and only takes a couple of steps.

On commons we record the location of the camera as accurately as we can. The locations of subjects should be geocoded on their Wikipedia articles, and the commons description should link to those Wikipedia articles.

[edit] Automatic procedures

GPS or other automated methods can be especially useful in rural locations without landmarks which can be easily recognized in the aerial images. If your camera has a built-in GPS receiver then your work is already done. User:DschwenBot goes through all new uploads every other day and adds the proper Geocoding Templates from the GPS data stored in your images. {{GPS EXIF}} can be added to make sure the bot visits a given image.

You can also use a separate GPS receiver to record the location while you are recording the media, and use computer software to merge the locations into the image files. Such software uses the camera time tag in the image file to look up the coordinates from the GPS. For accurate results, the camera time must be correct or the time error entered manually. The time error can be monitored by photographing the time displayed by the GPS. Errors caused by spotty GPS coverage can be adjusted by the same tools that are used for manual geocoding, though more easily since you already have an approximate position.

[edit] Adding Geotags before uploading

Some software, such as a combination of Picasa and Google Earth, allow you to add geographical information to images. The bot will also recognize these tags. You cannot add camera direction by this procedure. However, the program Geosetter can include in the images files (JPG mainly) many metadata including : geographic coordinates of the location shooting, camera direction, the name of the exact location, etc..., like the program named Microsoft Pro Photo Tools.

If your camera has accidentally tagged your images with completely wrong geodata, you can remove them on a batch of pictures by using ExifToolGUI. It uses ExifTool that is also installed by Geosetter mentioned above.

[edit] Fully manual procedure

The easiest way to identify the location in urban areas is to use an online mapping site with aerial imaging such as:

[edit] GeoLocator tool

Steps to obtain coordinates and build appropriate location tag:

  1. find your location on embedded map (move/zoom/search it as needed)
  2. place location marker on most exact location ([Alt+click] over your location, or by dragging a marker)
  3. define heading (camera view direction) from that location ([Shift+mouse move]/[Shift+click])
  4. copy resulting {{location}} or {{location dec}} markup

Steps to update an existing location tag (to improve location or to add heading):

  1. paste existing location tag into query box and press Apply. Tag gets parsed and location will appear on a map.
  2. update location marker to more exact location (by dragging it or by [Alt+click] over new location)
  3. define heading (camera view direction) from that location ([Shift+mouse move]/[Shift+click])
  4. copy resulting {{location}} or {{location dec}} markup back

[edit] hjl_geocoding tool

Three steps to get coordinates:

  1. search your location within the map
  2. click on location d or location dms button
  3. copy text
  4. replace location d with location dec and location dms with location

Notes

[edit] WikiMapia

[edit] Recommended method (with Firefox)

[edit] Manual method

[edit] Google Maps

[edit] Method 1

  1. Go to Google Maps with crosshair
  2. Zoom-in to the lowest resolution over the place you want to geotag by double-clicking on the map
  3. Place the cross hair exactly over the place and click on it.
  4. Two templates will be shown one in {{coor dms}} and one in {{Location}} format.
  5. Copy {{Location}} template and paste it below {{Information}} template of your file.
  6. In case you are geo tagging categories or galleries, {{coor dms}} might be more suitable.

[edit] Method 2

  1. Create a new bookmark of any page and give it name like Geocoding
  2. Find the bookmark in your bookmark list and access its properties ( on PC in Firefox or Internet Explorer this is done by right-clicking on the bookmark and choosing Properties)
  3. Modify the location or URL field by entering:
javascript:void(prompt('',"{{location dec|" + gApplication.getMap().getCenter().lat() + "|" + gApplication.getMap().getCenter().lng() + "}}"));
  1. If your browser (like Firefox) supports bookmarklets, it may be helpful to save this bookmark in the toolbar, for easy one-click access.
  1. Open a new browser tab/window and load http://maps.google.com/.
  2. Search for the correct location.
  3. Click on "Satellite" if it helps to find the location more easily, and zoom in.
  4. Click on the exact location the media was recorded to center the map.
  5. Click on your bookmark and you'll get a prompt with the geocode tag to add to the image.

[edit] Method 3

  1. Open a new browser tab/window and load http://maps.google.com/.
  2. Search for the correct location.
  3. Click "Satellite" and zoom it.
  4. Click on the exact location the media was recorded to center the map.
  5. Click "Link to this page"
  6. Now, either:
  • Look in the url for a string like ll=37.51136,-77.602615. The numbers are latitude, longitude; you have identified the location.
  • Or, use the Coordinate conversion helper which assists you with the geocoding process. Check the page for instructions on installing and using it.

[edit] Google Earth

See en:Wikipedia:Obtaining geographic coordinates for more information.

[edit] Precision

The linear measurement of a longitudinal angle varies according to Latitude. If we are aiming to a precision of about 7 m, then it is appropriate to use decimal degrees with 4 decimal places. This is suitable in most cases.

Length Equivalent of Longitudinal Degree at Selected Latitudes in km
Latitude Town Degree ° Minute ' Second " Decimal Degree at 4 dp
60 Saint Petersburg 55.65 km 0.927 km 15.42 m 5.56 m
51° 28' 38" N Greenwich 69.29 km 1.155 km 19.24 m 6.93 m
45 Bordeaux 78.7 km 1.31 km 21.86 m 7.87 m
30 New Orleans 96.39 km 1.61 km 26.77 m 9.63 m
0 Quito 111.3 km 1.855 km 30.92 m 11.13 m

Note that latitudinal degrees do not vary significantly across the Earth, having a surface precision of 1" = 31 m or 0.0001° = 11 m. See en:Geographic coordinate system for more information.

[edit] Geodetic system

All coordinates should be referenced to the en:WGS84 datum, the one supported by GPS systems and Google Maps. References taken from printed maps are unlikely to use this datum, and lead to inaccuracies in the order of hundreds of metres. National Grid reference systems use a local datum so will provide the wrong result.

[edit] Adding a location template

The use of the following templates is encouraged:

Do not simply invent your own new templates or copy geocoding templates from other wikis without discussion. Doing so can break the automation that reads and uses the geocoding. Commons geocoding needs are also not the same as those of other projects. Note that you should also not create your own wrappers around {{Location}} or {{Location dec}}; this will break the automation as well. Just call one of the templates directly from the image description page.

Simply add {{location dec|lat|long}} to the image page, filling in the lat and long from the procedure above. If the image page has an {{Information}} template, or similar, the {{location}} template should come immediately after it. The result will look something like this:

Camera location

37° 30' 40.9" N, 77° 36' 9.41" W

 This and other images at their locations on: Google Maps - Google Earth (Info)

Alternatively, add {{location|lat deg|lat min|lat sec|NS|long deg|long min|long sec|EW}} to the image page, filling in the lat and long. If the image page has an {{Information}} template, or similar, the {{location}} template should come immediately after it. The result will look something like this:

Camera location

37° 30' 40.9" N, 77° 36' 9.41" W

 This and other images at their locations on: Google Maps - Google Earth (Info)
Compass points

[edit] Parameters

Wikipedia geocoding often uses parameters after the coordinates to give more information about the location, but some of them are not useful here.

[edit] Heading parameter related tools

[edit] Use of the information

Clicking on the coordinates on an Image page will lead to a list of various services that can show the location. It is also possible to browse Commons images on a map:

[edit] Things to do

[edit] Special:Preferences

Some of the tools can be activate in the "gadget" tab of Special:Preferences:

[edit] Participants

Geocoded images on Commons

[edit] See also

Retrieved from "http://commons.wikimedia.org/wiki/Commons:Geocoding"
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