geo_polygon_centroid()

  • Article

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

Calculates the centroid of a polygon or a multipolygon on Earth.

Syntax

geo_polygon_centroid(polygon)

Learn more about syntax conventions.

Parameters

Name Type Required Description
polygon dynamic ✔️ Polygon or multipolygon in the GeoJSON format.

Returns

The centroid coordinate values in GeoJSON Format and of a dynamic data type. If polygon or multipolygon are invalid, the query produces a null result.

Note

  • The geospatial coordinates are interpreted as represented by the WGS-84 coordinate reference system.
  • The geodetic datum used for measurements on Earth is a sphere. Polygon edges are geodesics on the sphere.
  • If input polygon edges are straight cartesian lines, consider using geo_polygon_densify() to convert planar edges to geodesics.
  • If input is a multipolygon and contains more than one polygon, the result will be the centroid of polygons union.

Polygon definition and constraints

dynamic({"type": "Polygon","coordinates": [ LinearRingShell, LinearRingHole_1, ..., LinearRingHole_N ]})

dynamic({"type": "MultiPolygon","coordinates": [[ LinearRingShell, LinearRingHole_1, ..., LinearRingHole_N], ..., [LinearRingShell, LinearRingHole_1, ..., LinearRingHole_M]]})

  • LinearRingShell is required and defined as a counterclockwise ordered array of coordinates [[lng_1,lat_1],...,[lng_i,lat_i],...,[lng_j,lat_j],...,[lng_1,lat_1]]. There can be only one shell.
  • LinearRingHole is optional and defined as a clockwise ordered array of coordinates [[lng_1,lat_1],...,[lng_i,lat_i],...,[lng_j,lat_j],...,[lng_1,lat_1]]. There can be any number of interior rings and holes.
  • LinearRing vertices must be distinct with at least three coordinates. The first coordinate must be equal to the last. At least four entries are required.
  • Coordinates [longitude, latitude] must be valid. Longitude must be a real number in the range [-180, +180] and latitude must be a real number in the range [-90, +90].
  • LinearRingShell encloses at most half of the sphere. LinearRing divides the sphere into two regions and chooses the smaller of the two regions.
  • LinearRing edge length must be less than 180 degrees. The shortest edge between the two vertices is chosen.
  • LinearRings must not cross and must not share edges. LinearRings might share vertices.

Examples

The following example calculates the Central Park centroid in New York City.

let central_park = dynamic({"type":"Polygon","coordinates":[[[-73.9495,40.7969],[-73.95807266235352,40.80068603561921],[-73.98201942443848,40.76825672305777],[-73.97317886352539,40.76455136505513],[-73.9495,40.7969]]]});
print centroid = geo_polygon_centroid(central_park)

Output

centroid
{"type": "Point", "coordinates": [-73.965735689907618, 40.782550538057812]}

The following example calculates the Central Park centroid longitude.

let central_park = dynamic({"type":"Polygon","coordinates":[[[-73.9495,40.7969],[-73.95807266235352,40.80068603561921],[-73.98201942443848,40.76825672305777],[-73.97317886352539,40.76455136505513],[-73.9495,40.7969]]]});
print 
centroid = geo_polygon_centroid(central_park)
| project lng = centroid.coordinates[0]

Output

lng
-73.9657356899076

The following example performs union of polygons in multipolygon and calculates the centroid of the unified polygon.

let polygons = dynamic({"type":"MultiPolygon","coordinates":[[[[-73.9495,40.7969],[-73.95807266235352,40.80068603561921],[-73.98201942443848,40.76825672305777],[-73.97317886352539,40.76455136505513],[-73.9495,40.7969]]],[[[-73.94262313842773,40.775991804565585],[-73.98107528686523,40.791849155467695],[-73.99600982666016,40.77092185281977],[-73.96150588989258,40.75609977566361],[-73.94262313842773,40.775991804565585]]]]});
print polygons_union_centroid = geo_polygon_centroid(polygons)

Output

polygons_union_centroid
"type": "Point", "coordinates": [-73.968569587829577, 40.776310752555119]}

The following example visualizes the Central Park centroid on a map.

let central_park = dynamic({"type":"Polygon","coordinates":[[[-73.9495,40.7969],[-73.95807266235352,40.80068603561921],[-73.98201942443848,40.76825672305777],[-73.97317886352539,40.76455136505513],[-73.9495,40.7969]]]});
print 
centroid = geo_polygon_centroid(central_park)
| render scatterchart with (kind = map)

Output

Screenshot of New York City Central park centroid.

The following example returns true because of the invalid polygon.

print isnull(geo_polygon_centroid(dynamic({"type": "Polygon","coordinates": [[[0,0],[10,10],[10,10],[0,0]]]})))

Output

print_0
true