geo_closest_point_on_line()

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

Calculates a point on a line or a multiline, which is closest to a given point on Earth.

Syntax

geo_closest_point_on_line(longitude,latitude,lineString)

Learn more about syntax conventions.

Parameters

Name Type Required Description
longitude real ✔️ The geospatial coordinate longitude value in degrees. A valid value is in the range [-180, +180].
latitude real ✔️ The geospatial coordinate latitude value in degrees. A valid value is in the range [-90, +90].
lineString dynamic ✔️ A line or multiline in the GeoJSON format.

Returns

A point in GeoJSON Format and of a dynamic data type on a line or multiline which is the closest to a given point on Earth. If the coordinate or lineString 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 to measure distance on Earth is a sphere. Line edges are geodesics on the sphere.
  • If input line edges are straight cartesian lines, consider using geo_line_densify() in order to convert planar edges to geodesics.
  • In order to calculate a distance between the closest point on a line or multiline to a given point, use geo_distance_point_to_line()

LineString definition and constraints

dynamic({"type": "LineString","coordinates": [[lng_1,lat_1], [lng_2,lat_2],..., [lng_N,lat_N]]})

dynamic({"type": "MultiLineString","coordinates": [[line_1, line_2, ..., line_N]]})

  • LineString coordinates array must contain at least two entries.
  • Coordinates [longitude, latitude] must be valid where longitude is a real number in the range [-180, +180] and latitude is a real number in the range [-90, +90].
  • Edge length must be less than 180 degrees. The shortest edge between the two vertices is chosen.

Tip

  • Using literal LineString or a MultiLineString may result in better performance.

Examples

The following example finds the point on a road which is the closest to North Las Vegas Airport.

Screenshot of a map showing the distance between North Las Vegas Airport and a specific road.

Run the query

print point_on_line = geo_closest_point_on_line(-115.199625, 36.210419, dynamic({ "type":"LineString","coordinates":[[-115.115385,36.229195],[-115.136995,36.200366],[-115.140252,36.192470],[-115.143558,36.188523],[-115.144076,36.181954],[-115.154662,36.174483],[-115.166431,36.176388],[-115.183289,36.175007],[-115.192612,36.176736],[-115.202485,36.173439],[-115.225355,36.174365]]}))

Output

point_on_line
{ "type": "Point", "coordinates": [ -115.192612, 36.176736]}

The following example returns a null result because of the invalid LineString input.

Run the query

print isnull(geo_closest_point_on_line(1,1, dynamic({ "type":"LineString"})))

Output

result
true

The following example returns a null result because of the invalid coordinate input.

Run the query

print result = isnull(geo_closest_point_on_line(300, 3, dynamic({ "type":"LineString","coordinates":[[1,1],[2,2]]})))

Output

result
true
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