geo_h3cell_children()

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Applies to: ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel

Calculates the H3 cell children.

Read more about H3 Cell.

Syntax

geo_h3cell_children(h3cell,resolution)

Learn more about syntax conventions.

Parameters

Name Type Required Description
h3cell string ✔️ An H3 Cell token value as it was calculated by geo_point_to_h3cell().
resolution int Defines the requested children cells resolution. Supported values are in the range [1, 15]. If unspecified, an immediate children token will be calculated.

Returns

Array of H3 Cell children tokens. If the H3 Cell is invalid or child resolution is lower than given cell, the query will produce a null result.

Note

A difference between cell resolution and its children can't be more than 5. A difference of 5 levels will be resulted in up to 16807 children tokens.

Examples

The following example calculates the H3 cell children.

Run the query

print children = geo_h3cell_children('862a1072fffffff')

Output

children
[ "872a10728ffffff", "872a10729ffffff", "872a1072affffff", "872a1072bffffff", "872a1072cffffff", "872a1072dffffff", "872a1072effffff" ]

The following example counts children 3 levels below a given cell.

Run the query

let h3_cell = '862a1072fffffff'; 
print children_count = array_length(geo_h3cell_children(h3_cell, geo_h3cell_level(h3_cell) + 3))

Output

children_count
343

The following example assembles GeoJSON geometry collection of H3 Cell children polygons.

Run the query

print children = geo_h3cell_children('862a1072fffffff')
| mv-expand children to typeof(string)
| project child = geo_h3cell_to_polygon(children)
| summarize h3_hash_polygon_lst = make_list(child)
| project geojson = bag_pack(
    "type", "Feature",
    "geometry", bag_pack("type", "GeometryCollection", "geometries", h3_hash_polygon_lst),
    "properties", bag_pack("name", "H3 polygons collection"))

Output

geojson
{ "type": "Feature", "geometry": { "type": "GeometryCollection", "geometries": [ ... ... ... ] }, "properties": { "name": "H3 polygons collection" }}

The following example returns true because of the invalid cell.

Run the query

print is_null = isnull(geo_h3cell_children('abc'))

Output

is_null
1

The following example returns true because the level difference between cell and its children is more than 5.

Run the query

print is_null = isnull(geo_h3cell_children(geo_point_to_h3cell(1, 1, 9), 15))

Output

is_null
1
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