50_Geohash_mapping.asciidoc

Mapping Geohashes

The first step is to decide just how much precision you need. Although you could index all geo-points with the default full 12 levels of precision, do you really need to be accurate to within a few centimeters? You can save yourself a lot of space in the index by reducing your precision requirements to something more realistic, such as 1km:

PUT /attractions
{
  "mappings": {
    "restaurant": {
      "properties": {
        "name": {
          "type": "string"
        },
        "location": {
          "type":               "geo_point",
          "geohash_prefix":     true, (1)
          "geohash_precision":  "1km" (2)
        }
      }
    }
  }
}

1. Setting geohash_prefix to true tells Elasticsearch to index all geohash prefixes, up to the specified precision.

2. The precision can be specified as an absolute number, representing the length of the geohash, or as a distance. A precision of 1km corresponds to a geohash of length 7.

With this mapping in place, geohash prefixes of lengths 1 to 7 will be indexed, providing geohashes accurate to about 150 meters.