Fast and Readable Geographical Hashing (CTA-5009-A)

Geographical hashes (“Geohashes”) are short strings of letters and digits that identify a specific geographic region. Geohashing has historically been described in implementations as well as in a relatively comprehensive article on Wikipedia. These are excellent resources, but they can change over time and are not generally suitable for building on in a consensus-based standards-making process.

 This document exists to remediate that. It describes the practice as it exists at the time of writing and provides general, straightforward algorithms for understanding and communicating with Geohashes. It also exists to serve as a stable reference document for a few IANA registrations. To that end, the algorithm documented in the “Technical description” section of the Geohash Wikipedia entry is described here. This document does not describe all the usages, limitations, or geographic and mathematical details for Geohashes because those are well described by the references.