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Short text encoding of geographic coordinates
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The Open Location Code (OLC) is a geocode based on a system of regular grids for identifying an area anywhere on the Earth.[1] It was developed at Google's Zürich engineering office,[2] and released late October 2014.[3] Location codes created by the OLC system are referred to as PlusCodes.
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 latitude and longitude. PlusCodes 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.[4]
Plus Codes are derived from latitude and longitude coordinates, so they already exist everywhere.[5] They are similar in length to a telephone number (e.g., 849VCWC8+R9) but can often be shortened to only four or six digits when combined with a locality (e.g., 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.[6] Since August 2015, Google Maps has supported Plus Codes in its search engine.[7] 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[8] and is available on GitHub.[9]
The Open Location Code system[15] is based on latitudes and longitudes in 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 has blocks of 20 by 20 degrees (9 rows and 18 columns), and is divided in 20 by 20 subblocks up to four times. From that level onwards, division is in 5 by 4 subblocks. The table shows the various block sizes at their maximum near the equator. The block width decreases with distance from the equator.
The full grid uses offsets from the 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.
Mapping of Plus Codes
Base 10 digit
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Base 20 digit
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
G
H
I
J
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. The biggest blocks have just two digits. 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:
Division of subblocks in PlusCodes
longitude →
latitude →
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 replacing an even number of trailing digits before the + sign with the digit 0, with nothing after the + sign.
Example
Consider, for example, zooming in on the Merlion fountain (1°17′12″N103°51′16″E / 1.286785°N 103.854503°E / 1.286785; 103.854503) in Singapore, which has Plus 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 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 6PH50000+.
After four further refinements, one lands on Merlion Park as 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".
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 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 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 geocoding databases which map names to latitude and longitude. Disambiguation requires narrowing the possibilities to within about 40km of the referenced location. The coordinates of the user's current location can be also used for context, if applicable.[17][18]
Comparison
Ex.
Plus Codes
Valid digits
Shortened codes
Precision
Point of interest
Street address
Lat/long of centroid
1
87C4VXQ7+QV
10
VXQ7+QV, Washington, District of Columbia, USA
6 digits
(14 m)
Washington Monument
2 15th St NW, Washington, DC 20024, United States
38.889437,-77.035313
2
9C3XGV3C+8X
10
GV3C+8X, London, United Kingdom
6 digits
(14 m)
10 Downing Street
10 Downing St, London SW1A 2AA, United Kingdom
51.503312,-0.127562
3
7GHXG559+4VQ
11
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
8FWMQRCQ+JRV
11
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
8Q7XMP52+J7CC
12
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
37QH5M6Q+54X3X
13
5M6Q+54XYX, Ushuaia, Tierra del Fuego Province, Argentina
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