geo_point_to_geohash()

Calculates the geohash string value of a geographic location.

Read more about geohash.

Syntax

geo_point_to_geohash(longitude, latitude,[ accuracy ])

Learn more about syntax conventions.

Parameters

Name	Type	Required	Description
longitude	real	✔️	Geospatial coordinate, longitude value in degrees. Valid value is a real number and in the range [-180, +180].
latitude	real	✔️	Geospatial coordinate, latitude value in degrees. Valid value is a real number and in the range [-90, +90].
accuracy	int		Defines the requested accuracy. Supported values are in the range [1, 18]. If unspecified, the default value 5 is used.

Returns

The geohash string value of a given geographic location with requested accuracy length. If the coordinate or accuracy is invalid, the query produces an empty result.

Note

• Geohash can be a useful geospatial clustering tool.
• Geohash has 18 accuracy levels with area coverage ranging from 25 Million km² at the highest level 1 to 0.6 μ² at the lowest level 18.
• Common prefixes of geohash indicate proximity of points to each other. The longer a shared prefix is, the closer the two places are. Accuracy value translates to geohash length.
• Geohash is a rectangular area on a plane surface.
• Invoking the geo_geohash_to_central_point() function on a geohash string that was calculated on longitude x and latitude y won't necessarily return x and y.
• Due to the geohash definition, it's possible that two geographic locations are very close to each other but have different geohash codes.

Geohash rectangular area coverage per accuracy value:

Accuracy	Width	Height
1	5000 km	5000 km
2	1250 km	625 km
3	156.25 km	156.25 km
4	39.06 km	19.53 km
5	4.88 km	4.88 km
6	1.22 km	0.61 km
7	152.59 m	152.59 m
8	38.15 m	19.07 m
9	4.77 m	4.77 m
10	1.19 m	0.59 m
11	149.01 mm	149.01 mm
12	37.25 mm	18.63 mm
13	4.66 mm	4.66 mm
14	1.16 mm	0.58 mm
15	145.52 μ	145.52 μ
16	36.28 μ	18.19 μ
17	4.55 μ	4.55 μ
18	1.14 μ	0.57 μ

See also geo_point_to_s2cell(), geo_point_to_h3cell().

For comparison with other available grid systems, see geospatial clustering with Kusto Query Language.

Examples

The following example finds US storm events aggregated by geohash.

Run the query

StormEvents
| project BeginLon, BeginLat
| summarize by hash=geo_point_to_geohash(BeginLon, BeginLat, 3)
| project geo_geohash_to_central_point(hash)
| render scatterchart with (kind=map)

Output

The following example calculates and returns the geohash string value.

Run the query

print geohash = geo_point_to_geohash(-80.195829, 25.802215, 8)

Output

geohash
dhwfz15h

The following example finds groups of coordinates. Every pair of coordinates in the group resides in a rectangular area of 4.88 km by 4.88 km.

Run the query

datatable(location_id:string, longitude:real, latitude:real)
[
  "A", double(-122.303404), 47.570482,
  "B", double(-122.304745), 47.567052,
  "C", double(-122.278156), 47.566936,
]
| summarize count = count(),                                          // items per group count
            locations = make_list(location_id)                        // items in the group
            by geohash = geo_point_to_geohash(longitude, latitude)    // geohash of the group

Output

geohash	count	locations
c23n8	2	["A", "B"]
c23n9	1	["C"]

The following example produces an empty result because of the invalid coordinate input.

Run the query

print geohash = geo_point_to_geohash(200,1,8)

Output

geohash

The following example produces an empty result because of the invalid accuracy input.

Run the query

print geohash = geo_point_to_geohash(1,1,int(null))

Output

geohash