View source for Earth:Open Location Code

{{Short description|Short text encoding of geographic coordinates}}
[[File:Plus Codes Logo.svg|thumb|Plus Codes logo]]
The '''Open Location Code''' ('''OLC''') is a geocode based on a system of regular grids for identifying an area anywhere on the Earth.<ref>{{cite web|url=http://plus.codes|title=Plus Codes|access-date=3 November 2018}}</ref>
It was developed at Google's [[Place:Zürich|Zürich]] engineering office,<ref>{{cite web|url=http://openlocationcode.com/|title=Open Location Code|website=Openlocationcode.com|archive-url=https://web.archive.org/web/20180301114837/http://openlocationcode.com/ |archive-date=1 March 2018 |url-status=dead}}</ref> and released late October 2014.<ref>See [https://github.com/google/open-location-code/commits/main Open Location Code GitHub] and [https://groups.google.com/d/forum/open-location-code Open Location Code forum].</ref> Location codes created by the OLC system are referred to as '''Plus{{nbsp}}Codes'''.

Open Location Code is a way of encoding location into a form that is easier to use than showing coordinates in the usual form of [[Earth:Geographic coordinate system|latitude and longitude]]. Plus{{nbsp}}Codes are designed to be used like street addresses and may be especially useful in places where there is no formal system to identify buildings, such as street names, house numbers, and post codes.<ref>The [http://openlocationcode.com/ Open Location Code website] provides an overview. The document [https://github.com/google/open-location-code/wiki/Evaluation-of-Location-Encoding-Systems "An Evaluation of Location Encoding Systems"] provides a rationale.</ref>

Plus Codes are differently expressed latitude and longitude coordinates, so they can be assigned to any location.<ref>{{cite report| title=Open Location Code: An Open Source Standard for Addresses, Independent of Building Numbers And Street Names|first1=Doug|last1=Rinckes|first2=Philipp|last2=Bunge|publisher=GitHub | date=30 September 2014<!--from page source--> | url=https://github.com/google/open-location-code/blob/main/Documentation/Specification/olc_definition.adoc}}</ref> They are similar in length to a telephone number (e.g., {{code|849VCWC8+R9}}) but can often be shortened to only four or six digits when combined with a locality (e.g., {{code|CWC8+R9, Mountain View, California}}). Locations close to each other have similar codes. They can be encoded or decoded offline. The character set avoids similar-looking characters to reduce confusion and errors and avoids vowels to make it unlikely that a code spells existing words. Plus Codes are not case-sensitive and can therefore be easily exchanged over the phone.<ref>{{cite web|url=http://google-opensource.blogspot.ch/2015/04/open-location-code-addresses-for.html|title=Open Location Code: Addresses for everything, everywhere|first=Doug|last=Rinckes|website=Google-opensource.blogspot.ch|date=30 April 2015}}</ref>
Since August 2015, Google Maps has supported Plus Codes in its search engine.<ref>{{cite web|url=http://google-latlong.blogspot.in/2015/08/plus-codes-new-way-to-help-pinpoint.html|title=Plus codes: A new way to help pinpoint places on the map|first=Rasťo|last=Šrámek|website=Google-latlong.blogspot.in|date=12 August 2015}}</ref> The shortened Plus Code is displayed for a location, may be copied, clicked, or transcribed, and can be entered into the address box (followed by the town or city name if not local and using shortened code) to display the location on the map. The algorithm is licensed under the Apache License 2.0 and is available on GitHub.<ref name=":0">{{cite web |title=google/open-location-code |url=https://github.com/google/open-location-code/blob/main/LICENSE |access-date=3 November 2018 |website=GitHub.com}}</ref>

==Applications==
Plus Codes are increasingly being used for addressing purposes in places that aren't well-served by the traditional street address system. This includes the many unnamed streets in Cape Verde,<ref>{{Cite web |date=December 1, 2016 |title=Delivering mail where the streets have no name |url=https://africa.googleblog.com/2016/12/delivering-mail-where-streets-have-no.html |website=Google Africa Blog}}</ref> multiple [[Engineering:Slum|slum]]s in [[Place:India|India]],<ref>{{Cite web|url=https://www.youtube.com/watch?v=Hd3gGspgVGs|title=Plus Codes &#124; Addressing in Kolkata|date=28 August 2018 |via=YouTube}}</ref><ref name="Abhyankar" /><ref>{{Cite web |last=Pathak |first=Sushmita |date=July 15, 2022| title=The Address of the Future |url=https://reasonstobecheerful.world/the-address-of-the-future/ |website=Reasons to be Cheerful}}</ref> and even some Native American reservations in the United States.<ref>{{cite news| last=Podmore | first=Zak | title=The Navajo Nation is getting addresses, thanks to an open-source mapping program used in urban India | newspaper=The Salt Lake Tribune | date=2019-10-25 | url=https://www.sltrib.com/news/2019/10/25/navajo-nation-is-getting/}}</ref> In Laxmi Nagar, Pune, the nonprofit Shelter Associates used codes to bring delivery services to specific homes and businesses in the slum for the first time in 2020-21.<ref name="Abhyankar">{{cite magazine |title="Addressing India's Slums" |author=Shoma Abhyankar |issue=3, May/June 2021 |volume=124 |magazine=MIT Technology Review |page=25 |url=https://www.technologyreview.com/2021/04/28/1022940/slum-dwellers-india-google-plus-code-access-delivery-apps/}}</ref> Plus{{nbsp}}Codes are also being used by the International Rescue Committee in Somalia for [[Finance:Immunization|immunization]] and family planning programs.<ref name="Abhyankar" />

==Specification==
The Open Location Code system<ref name=":0" /> is based on latitudes and longitudes in [[World Geodetic System#WGS84|WGS84]] coordinates. Each code describes an area bounded by two parallels and two meridians out of a fixed grid, identified by the southwest corner and its size. The largest grid divides the globe into blocks of 20 by 20 degrees, 18 columns from West to East and 9 rows from the South to the North poles. Those large blocks are then subdivided into 400 subblocks, 20 by 20, up to four times. Near the equator, those subblocks are square both in degrees and in meters. At midlatitudes, while still square in terms of degrees, in terms of ground distance the blocks are not as wide as they are tall.

After the initial division and four rounds of 20x20 subdivision (via two code characters each round), further subdivisions break each block into 20 subblocks (via one code character), 4 blocks W-E by 5 blocks S-N. That leaves the subblocks wider than they are tall in terms of degrees, but at midlatitudes, this keeps them closer to square in terms of meters. The table shows the various block sizes near the equator, where the widths are maximum (listing width x height where those differ). The block widths decrease with distance from the equator.

{| class="wikitable"
|+Block sizes of Plus Codes<ref>{{Cite web |title=open-location-code/Documentation/Specification/specification.md at main · google/open-location-code |url=https://github.com/google/open-location-code/blob/main/Documentation/Specification/specification.md |access-date=2025-01-08 |website=GitHub |language=en}}</ref>
! style="text-align: left" | Code length
| 2 || 4 || 6 || 8 || + || 10 || 11
|12
|13
|14
|15
|-
! style="text-align: left" | Block size
| 20° || 1° || 0.05° (3′) || 0.0025° (9″) || || 0.000125° (0.45″) || 0.1125″
|0.0281″
|0.0070″
|0.0018″
|0.0004″
|-
! style="text-align: left" | Real size
| 2,200&nbsp;km || 110&nbsp;km || 5.6 km || 280 m || || 14 m || 3.5 m × 2.8 m
|0.8 m × 0.5 m
|20 cm × 10 cm
|5 cm × 2 cm
|14 mm × 4 mm
|}

The full grid uses offsets from the [[Earth:South Pole|South Pole]] (−90°) and the antimeridian (−180°) expressed in base 20 representation. To avoid misreading or spelling objectionable words, the encoding excludes vowels and symbols that may be easily confused with each other. The following table shows the mapping.

{| class="wikitable"
|+Mapping of Plus Codes
|-
! style="text-align: left" | Base 10 digit
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7 || 8 || 9 || 10 || 11 || 12 || 13 || 14 || 15 || 16 || 17 || 18 || 19
|-
! style="text-align: left" | Base 20 digit
| 0 || 1 || 2 || 3 || 4 || 5 || 6 || 7 || 8 || 9 || A || B || C || D || E || F || G || H || I || J
|-
! style="text-align: left" | Code digit
| 2 || 3 || 4 || 5 || 6 || 7 || 8 || 9 || C || F || G || H || J || M || P || Q || R || V || W || X
|}

The code begins with up to five pairs of digits, each consisting of one digit representing latitude and one representing longitude. After eight digits, a plus sign "+" is inserted in the code as a delimiter to aid with visual parsing. After a final pair immediately following the "+" delimiter, any subblocks thereafter are coded in a single code digit as follows:

{| class="wikitable"
|+Division of subblocks in Plus{{nbsp}}Codes
!  || colspan="4" | longitude →
|-
! rowspan="5" {{verth|latitude →|va=top}}
| R || V || W || X
|-
| J || M || P || Q
|-
| C || F || G || H
|-
| 6 || 7 || 8 || 9
|-
| 2 || 3 || 4 || 5
|}

Areas larger than an 8-digit block can be specified by truncating the code after the relevant digit pairs and inserting the "padding character" 0 (zero) before the + sign, with nothing following it.

==Example==
Consider, for example, zooming in on the Merlion fountain ({{coord|1.286785|N|103.854503|E}}) in [[Place:Singapore|Singapore]], which has Plus Code {{code|6PH57VP3+PR6}}. It lies in the block around the equator bounded by −10° South and +10° North, and between 100° and 120° East. It has offsets 80° from the South Pole, and 280° from the anti-meridian; or, 4 (=80/20) and 14 (=280/20) as the first base-20 digits, coded as "6" and "P". Thus, the code is "6P". This may be padded as {{code|6P000000+}}.

Now, refine this block to a subblock between 1° and 2° N and 103° and 104° E. This adds 11° and 3° to the SW corner. So the base-20 coordinate codes added are "H" and "5". The result is padded to {{code|6PH50000+}}.

After four further refinements, one lands on Merlion Park as {{code|6PH57VP3+PR}}.

The next step requires dividing the square so far used, to refine the position into a 4-by-5 grid, and finding the cell to which the coordinates are pointing. This is the cell named "6". 

===BASE20 Formula===
Alternatively, use formula BASE(Degrees from South or West * power(20, 4) , 20) in any Spreadsheet or Calculator to compute the Plus Code. For the coordinates {{coord|1.286785|N|103.854503|E}} from the previous example:
* 1.286785N = 91.286785 from South Pole, in Base20 = 4B.5EE(5) in alphanumeric = which is 6H.7PP in OLC digits. 
* 103.854503E = 283.854503 from Anti-Meridian, in Base20 = E3.H1G(0) in alphanumeric = which is P5.V3R in OLC digits. 
* Combining latitude and longitude alternatively, 6P H5 7V P3 PR.
* The last leftover in Base20, (5)/20 latitude and (0)/20 longitude gives 6 in the 4-by-5 grid. 

Therefore, the resulting Plus Code is {{code|6PH57VP3+PR6}}.

==Common usage and shortening==

It is common to omit the first four characters from the code and add an approximate location, such as a city, state, or country. The above example then becomes {{code|7VP3+PR6 Singapore}}. This is supported by the Google Maps app and the plus.codes website, and also by non-Google apps. These short forms of Plus Codes can be used in lieu of a house number in a neighborhood.

Shortened codes cannot be unambiguously encoded or decoded without context. The specification does not rely on any specific database of contextual reference location place names and their exact locations, but there are a variety of [[Earth:Geocoding|geocoding]] databases which map names to latitude and longitude. Disambiguation requires narrowing the possibilities to within about 40&nbsp;km of the referenced location. The coordinates of the user's current location can be also used for context, if applicable.<ref>{{Cite web |last=Kegel |first=Mark |date=2019-09-24 |title=What's Wrong with Open Location Code? - QA Locate |url=https://www.qalocate.com/whats-wrong-with-open-location-code/ |access-date=2022-11-07 |language=en-US}}</ref><ref>{{Cite web |date=2019-04-21 |title=Open Location Code: An Open Source Standard for Addresses, Independent of Building Numbers And Street Names |website=[[GitHub]] |url=https://github.com/google/open-location-code/blob/main/docs/olc_definition.adoc#shortening-open-location-codes |access-date=2022-11-25 |language=en-US}}</ref> 

{| class="wikitable"
|+Comparison
!Ex.
!Plus Codes
!Valid<br>digits
!Shortened codes
!Precision
!Point of interest
!Street address
!Lat/long of centroid
|-
|1
| {{mono|87C4VXQ7+QV}}
|10
| {{mono|VXQ7+QV}}, Washington, District of Columbia, USA
|6 digits
(14 m)
|Washington Monument
|2 15th St NW, Washington, DC 20024, United States
|38.889437, &minus;77.035313
|-
|2
| {{mono|9C3XGV3C+8X}}
|10
| {{mono|GV3C+8X}}, London, United Kingdom
|6 digits
(14 m)
|10 Downing Street
|10 Downing St, London SW1A 2AA, United Kingdom
|51.503312, &minus;0.127562
|-
|3
| {{mono|7GHXG559+4VQ}}
|11
| {{mono|G559+4VQ}}, Al-Baghdadiyah Al-Gharbiyah, Jeddah, Saudi Arabia
|7 digits
(3.5 m)
|Jeddah Flagpole
|King Abdullah Bin Abdulaziz Square, Al-Baghdadiyah Al-Gharbiyah, Jeddah 22231, Saudi Arabia
|21.507813, 39.169688
|-
|4
| {{mono|8FWMQRCQ+JRV}}
|11
| {{mono|QRCQ+JRV}}, Schwarzenberg am Böhmerwald, Austria
|7 digits
(3.5 m)
|Tri-Border Czechia/Austria/Germany
|Tri-Border, 4164 Schwarzenberg am Böhmerwald, Austria
|48.771613, 13.839547
|-
|5
| {{mono|8Q7XMP52+J7CC}}
|12
| {{mono|MP52+J7CC}}, Shibuya, Tokyo, Japan
|8 digits
(87 cm)
|Hachikō Memorial Statue
|2 Chome-1 Dogenzaka, Shibuya, Tokyo 150-0043, Japan
|35.659063, 139.700688
|-
|6
| {{mono|37QH5M6Q+54X3X}}
|13
| {{mono|5M6Q+54XYX}}, Ushuaia, Tierra del Fuego Province, Argentina
|9 digits
(22 cm)
| {{sdash}}
| {{sdash}}
| &minus;54.83952050, &minus;68.31214160
|-
|7
| {{mono|6G8RJMMW+9V9V9V}}
|14
| {{mono|JMMW+9V9V9V}}, Arusha, Tanzania
|10 digits
(5 cm)
| {{sdash}}
| {{sdash}}
| &minus;3.36657810, 36.69723315
|-
|8
| {{mono|6P58QRJ3+H25FGFG}}
|15
| {{mono|QRJ3+H25FGFG}}, Jakarta, Indonesia
|11 digits
(14 mm)
| {{sdash}}
| {{sdash}}
| &minus;6.21861250, 106.80260626
|}

==References==
{{reflist}}

==External links==
*{{official}}, with a video explanation
*{{GitHub|google/open-location-code}}

{{Geocoding-systems}}

[[Category:Geographic coordinate systems]]

{{Sourceattribution|Open Location Code}}