GEOHASH key member [member …]

Available since 3.2.0.

Time complexity: O(log(N)) for each member requested, where N is the number of elements in the sorted set.

Return valid Geohash strings representing the position of one or more elements in a sorted set value representing a geospatial index (where elements were added using GEOADD).

Normally Redis represents positions of elements using a variation of the Geohash technique where positions are encoded using 52 bit integers. The encoding is also different compared to the standard because the initial min and max coordinates used during the encoding and decoding process are different. This command however returns a standard Geohash in the form of a string as described in the Wikipedia article and compatible with the geohash.org web site.

*Geohash string properties

The command returns 10 characters Geohash strings, so only two bits of precision are lost compared to the Redis internal 52 bit representation, but this loss doesn't affect the precision in a sensible way: normally geohashes are cut to up to 8 characters, giving anyway a precision of +/- 0.019 km.

  • Geo hashes can be shortened removing characters from the right. It will lose precision but will still point to the same area.
  • It is possible to use them in geohash.org URLs such as http://geohash.org/<geohash-string&gt;. This is an example of such URL.
  • Strings with a similar prefix are nearby, but the contrary is not true, it is possible that strings with different prefixes are nearby too.Note: older versions of Redis used to return 11 characters instead of 10, however because of a bug the last character was not correct and was not helping in having a better precision.

*Return value

Array reply, specifically:

The command returns an array where each element is the Geohash corresponding to each member name passed as argument to the command.

*Examples

redis> GEOADD Sicily 13.361389 38.115556 "Palermo" 15.087269 37.502669 "Catania" 

  1. (integer) 2

redis> GEOHASH Sicily Palermo Catania 

  1. 1) "sqc8b49rny0"
  2. 2) "sqdtr74hyu0"
redis>