Geohash

Geohash is a public domain geocoding system that encodes a geographic location (LatLong) into a short string of letters and digits (a base32 positive integer number).

Geohash is a de facto standard to enconde LatLong coordinates in only one number, accepted by PostGIS and many others tools.

Tools

OSM Tools:

• JOSM GeoHash plugin displays a layer on top of the JOSM map that contains the corresponding geohashes, up to a depth of 10. This means that the geohash can have a code length of maximum 10 characters.

• ... OSM's API to express Geohash as reliable short link? (see help.openstreetmap.org/questions/65670).

Non-OSM to OSM or general use:

• Functions ST_GeoHash(), ST_Box2dFromGeoHash() and ST_PointFromGeoHash() of PostGIS.

• Geohash.org offers the format=osm option. Example: http://geohash.org/w21z76281?format=osm

Non-OSM to other maps:

• Geohash.org
• https://www.movable-type.co.uk/scripts/geohash.html

Comparison with other solutions

Consider for example zooming in on the Singapure's Merlion (Wikidata Q208760), an ~8mx3m map feature, as element into the OpenStreetMap.

• 

  The OSM's map not show Geohash cell.

• 

  The Map Feature: Merlion sculpture and fountain.

• 

  At GoogleMap's zoom, in its Geohash cell of ~10m×5m.
  Using a 8-length code, w21z7628. The Singapure's Geohash cell is w2 prefix (or w21 excluding Pedra Branca island).

• 

  At openstreetmap.org/edit, the rose way.
  PS: as there are no Permanent ID you can try to link at osm.org/way/182819157 or look for wikidata tag Q208760.

• 

  At PlusCode interface, as ~2m×2m cell. Using a 11-length code, 6PH57VP3+PR6 and showing option of "cityName + localCell code" (city's local cell is the 6PH5 prefix).

Geohash is a kind of "hyerarchical-cells coordinate system", so can be compared with different "cell resources". Example:

• An ~10m×10m box of 6PH57VP3+PR, using PlusCode.
• An ~5m×5m box of w21z76281, using Geohash.

After 4 refinements one lands on Merlion park as 6PH57VP3+PR.
It is a 10 characters code, representing a ~10m×10m box. The same point of a ~5m×5m box in the Geohash representation, w21z76281, consumes 9 characters.

Solution	Template URL	Pros	Cons
Geohash at OSM - ideal OSM's redirection (is a fantasi, not exists)	OSM.ORG/G{geohashCode}	Short URL, good and precise zoom and renderization	(no relevant problem)
Geohash at Geohash.org - bad OSM's redirection	geohash.org/{geohashCode}	Short URL	No zoom, no cell renderization
Geohash at movable-type.co.uk/scripts - good renderization but no redirection	2	3	4
? Good zoom and renderization	(no redirection)	3	4
PlusCode	.../{PlusCode}	...	...
Mapcode	.../{Mapcode}	...	...
what3words ([Wikipedia](https://en.wikipedia.org/wiki/What3words))... Easy to remember...	2	3	4

IMPORTANT-1: Mapcode and What3words are patented systems, so they are not suject to selection or merit, only to technical analisis.

IMPORTANT-2: the What3words strategy to translate the geo-ID into dictionary words can be reproduced by any other code, using a non-copyrighted set of words of any language. It is good to write at Telegram or Whatsapp chats, but it is not a good choice for official ID of a Map Feature or address. So it its a "secondary ID" (translated), and can enhance and can be removed from comparisons.

Administrative names conventions

Standards like ISO_3166-2 when adopted for principal subdivisions (by for instance AD, AR, BR or CL), can be conjugated with city names or city-3-letter abbreviations to express a cell (so a prefix of internal cells), a reference system or a "local BBOX". For Singapure suppose SG or SG-1.

Solution - city	City mnemonic (len)	Prefix (len)	Complete Feature code (len)	Feature code (len)	Complete Feature alias (len)
Geohash - Singapure	SG-1 (3)	w21 (3)	w21z7628 (8)	z7628 (5)	SG1-Z7628 (8)
PlusCode - Singapure	Singapure (9)	6PH5 (4)	6PH57VP3+PR6 (11)	7VP3+PR6 (7)	7VP3+PR6 Singapure (16)
Adapted PlusCode - Singapure	SG-1 (3)	6PH5 (4)	6PH57VP3+PR6 (11)	7VP3+PR6 (7)	7VP3+PR6 SG-1 (10)
Mapcode - Singapure	SGP (3)	SPG (3)	HSF9S.TNMH (9)	NP.PZ (4)	SGP NP.PZ (7)