Functions for Working with Geohash 

Geohash is the geocode system, which subdivides Earth’s surface into buckets of grid shape and encodes each cell into a short string of letters and digits. It is a hierarchical data structure, so the longer is the geohash string, the more precise is the geographic location.

If you need to manually convert geographic coordinates to geohash strings, you can use geohash.org.

geohashEncode 

Encodes latitude and longitude as a geohash-string.

geohashEncode(longitude, latitude, [precision])

Input values

  • longitude - longitude part of the coordinate you want to encode. Floating in range[-180°, 180°]
  • latitude - latitude part of the coordinate you want to encode. Floating in range [-90°, 90°]
  • precision - Optional, length of the resulting encoded string, defaults to 12. Integer in range [1, 12]. Any value less than 1 or greater than 12 is silently converted to 12.

Returned values

  • alphanumeric String of encoded coordinate (modified version of the base32-encoding alphabet is used).

Example

SELECT geohashEncode(-5.60302734375, 42.593994140625, 0) AS res
┌─res──────────┐
│ ezs42d000000 │
└──────────────┘

geohashDecode 

Decodes any geohash-encoded string into longitude and latitude.

Input values

  • encoded string - geohash-encoded string.

Returned values

  • (longitude, latitude) - 2-tuple of Float64 values of longitude and latitude.

Example

SELECT geohashDecode('ezs42') AS res
┌─res─────────────────────────────┐
│ (-5.60302734375,42.60498046875) │
└─────────────────────────────────┘

geohashesInBox 

Returns an array of geohash-encoded strings of given precision that fall inside and intersect boundaries of given box, basically a 2D grid flattened into array.

Syntax

geohashesInBox(longitude_min, latitude_min, longitude_max, latitude_max, precision)

Parameters

  • longitude_min — Minimum longitude. Range: [-180°, 180°]. Type: Float.
  • latitude_min — Minimum latitude. Range: [-90°, 90°]. Type: Float.
  • longitude_max — Maximum longitude. Range: [-180°, 180°]. Type: Float.
  • latitude_max — Maximum latitude. Range: [-90°, 90°]. Type: Float.
  • precision — Geohash precision. Range: [1, 12]. Type: UInt8.

Returned values

  • Array of precision-long strings of geohash-boxes covering provided area, you should not rely on order of items.
  • [] - Empty array if minimum latitude and longitude values aren’t less than corresponding maximum values.

Type: Array(String).

Example

Query:

SELECT geohashesInBox(24.48, 40.56, 24.785, 40.81, 4) AS thasos

Result:

┌─thasos──────────────────────────────────────┐
│ ['sx1q','sx1r','sx32','sx1w','sx1x','sx38'] │
└─────────────────────────────────────────────┘

Original article

Rating: 4 - 1 votes

Was this content helpful?
★★★★☆