geo_intersection_2polygons()

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

Calculates the intersection of two polygons or multipolygons.

Syntax

geo_intersection_2polygons(polygon1,polygon1)

Learn more about syntax conventions.

Parameters

Name	Type	Required	Description
polygon1	dynamic	✔️	Polygon or multipolygon in the GeoJSON format.
polygon2	dynamic	✔️	Polygon or multipolygon in the GeoJSON format.

Returns

Intersection in GeoJSON Format and of a dynamic data type. If Polygon or a MultiPolygon are invalid, the query will produce a null result.

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.
• Polygon contains its vertices.

Examples

The following example calculates intersection between two polygons. In this case, the result is a polygon.

let polygon1 = dynamic({"type":"Polygon","coordinates":[[[-73.9630937576294,40.77498840732385],[-73.963565826416,40.774383111780914],[-73.96205306053162,40.773745311181585],[-73.96160781383514,40.7743912365898],[-73.9630937576294,40.77498840732385]]]});
let polygon2 = dynamic({"type":"Polygon","coordinates":[[[-73.96213352680206,40.775045280447145],[-73.9631313085556,40.774578106920345],[-73.96207988262177,40.77416780398293],[-73.96213352680206,40.775045280447145]]]});
print intersection = geo_intersection_2polygons(polygon1, polygon2)

Output

intersection
{"type": "Polygon", "coordinates": [[[-73.962105776437156,40.774591360999679],[-73.962642403166868,40.774807020251778],[-73.9631313085556,40.774578106920352],[-73.962079882621765,40.774167803982927],[-73.962105776437156,40.774591360999679]]]}

The following example calculates intersection between two polygons. In this case, the result is a point.

let polygon1 = dynamic({"type":"Polygon","coordinates":[[[2,45],[0,45],[1,44],[2,45]]]});
let polygon2 = dynamic({"type":"Polygon","coordinates":[[[3,44],[2,45],[2,43],[3,44]]]});
print intersection = geo_intersection_2polygons(polygon1, polygon2)

Output

intersection
{"type": "Point","coordinates": [2,45]}

The following two polygons intersection is a collection.

let polygon1 = dynamic({"type":"Polygon","coordinates":[[[2,45],[0,45],[1,44],[2,45]]]});
let polygon2 = dynamic({"type":"MultiPolygon","coordinates":[[[[3,44],[2,45],[2,43],[3,44]]],[[[1.192,45.265],[1.005,44.943],[1.356,44.937],[1.192,45.265]]]]});
print intersection = geo_intersection_2polygons(polygon1, polygon2)

Output

intersection
{"type": "GeometryCollection","geometries": [ { "type": "Point", "coordinates": [2, 45]}, { "type": "Polygon", "coordinates": [[[1.3227075526410679,45.003909145068739],[1.0404565374899824,45.004356403066552],[1.005,44.943],[1.356,44.937],[1.3227075526410679,45.003909145068739]]]}]}

The following two polygons don't intersect.

let polygon1 = dynamic({"type":"Polygon","coordinates":[[[2,45],[0,45],[1,44],[2,45]]]});
let polygon2 = dynamic({"type":"Polygon","coordinates":[[[3,44],[3,45],[2,43],[3,44]]]});
print intersection = geo_intersection_2polygons(polygon1, polygon2)

Output

intersection
{"type": "GeometryCollection", "geometries": []}

The following example finds all counties in USA that intersect with area of interest polygon.

let area_of_interest = dynamic({"type":"Polygon","coordinates":[[[-73.96213352680206,40.775045280447145],[-73.9631313085556,40.774578106920345],[-73.96207988262177,40.77416780398293],[-73.96213352680206,40.775045280447145]]]});
US_Counties
| project name = features.properties.NAME, county = features.geometry
| project name, intersection = geo_intersection_2polygons(county, area_of_interest)
| where array_length(intersection.geometries) != 0

Output

name	intersection
New York	{"type": "Polygon","coordinates": [[[-73.96213352680206, 40.775045280447145], [-73.9631313085556, 40.774578106920345], [-73.96207988262177,40.77416780398293],[-73.96213352680206, 40.775045280447145]]]}

The following example will return a null result because one of the polygons is invalid.

let central_park_polygon = dynamic({"type":"Polygon","coordinates":[[[-73.9495,40.7969],[-73.95807266235352,40.80068603561921],[-73.98201942443848,40.76825672305777],[-73.97317886352539,40.76455136505513],[-73.9495,40.7969]]]});
let invalid_polygon = dynamic({"type":"Polygon"});
print isnull(geo_intersection_2polygons(invalid_polygon, central_park_polygon))

Output

print_0
1