Open Location Code (OLC) is a geocoding system that encodes latitude/longitude coordinates into a short string of typically 9-12 characters, the idea being that these strings can be communicated better than the latitude/longitude coordinates themselves.
Individual codes are also called plus codes, because the OLC specification mandates a ‘+’ character after the eighth code digit for easier identification. An example is the plus code 9F4MG98H+G3, encoding the location (52.516312,13.377688) – or rather, a small area of around 100m² including the location.
Full vs. Short codes
Full plus codes – codes with eight characters preceding the ‘+’ – are globally unique, and can be decoded offline and without any additional information. Alternatively, a reference location can be used to shorten plus codes by dropping leading characters.
This reference location needs to be known to properly decode the shortened plus code. It can be added to the end in form of a place name, in which case the example location given above becomes G98H+G3, Berlin. It may also be shared knowledge, for example when arranging a meeting in a certain city.
One promoted use case for short plus codes are postal services in regions where street adresses don’t exist. After getting a postal item to the correct city, a short plus code like G98H+G3M could be used within the city to identify the correct dwelling to deliver to.
Exact vs. coarse location
While plus codes are mostly designed to address a specific location, they can also be used to identify larger areas, by removing characters (or replacing them with ‘0’ as a padding character) from the end:
| example code | approximate size |
| 9F4MG98H+G3M | precise enough to identify a specific entrance to a building |
| 9F4MG98H+G3 | single-family house |
| 9F4MG98H+ | small neighborhood |
| 9F4MG900+ | city district |
| 9F4M0000+ | larger than Berlin, Germany |
| 9F000000+ | most of the Scandinavian peninsula plus surrounding seas, large parts of Germany, Poland, the Netherlands, Belgium etc. |
The multi-colored elephant in the room
The Open Location Code system was developed by one of Google’s engineering teams, and is actively used on Google Maps: you can search for any plus code, and points of interest will typically display their shortened plus code.
While that makes the use of short codes somewhat controversial – the typical argument being that decoding a short code will only work while having access to the same geocoding database that was used to shorten the code in the first place – it doesn’t affect the use of full plus codes at all, and is a mostly theoretical concern in many other scenarios.
