geo_polygon_perimeter()

  • Article
  • 09/30/2024

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

Calculates the length of the boundary of a polygon or a multipolygon on Earth.

Syntax

geo_polygon_perimeter(polygon)

Learn more about syntax conventions.

Parameters

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

Returns

The length of the boundary of polygon or a multipolygon, in meters, on Earth. If polygon or multipolygon are invalid, the query will produce 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 length of the boundary 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. The smaller of the two regions will be chosen.
  • LinearRing edge length must be less than 180 degrees. The shortest edge between the two vertices will be chosen.
  • LinearRings must not cross and must not share edges. LinearRings may share vertices.

Examples

The following example calculates the NYC Central Park perimeter, in meters.

Run the query

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 perimeter = geo_polygon_perimeter(central_park)

Output

perimeter
9930.30149604938

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

Run the query

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 perimeter = geo_polygon_perimeter(polygons)

Output

perimeter
15943.5384578745

The following example returns True because of the invalid polygon.

Run the query

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

Output

is_invalid
True