Open Location Code

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, multiple slums in India, and even some Native American reservations in the United States. 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. PlusCodes are also being used by the International Rescue Committee in Somalia for immunization and family planning programs. ==Specification==

The Open Location Code system 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 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, their angles remain square, but in terms of distance, they elongate vertically. 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. 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. 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: 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 () in Singapore, which has Plus Code . 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 . 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 . After four further refinements, one lands on Merlion Park as . 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 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 . ==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 . 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 40 km of the referenced location. The coordinates of the user's current location can be also used for context, if applicable. ==References==