geo_line_interpolate_point()

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

Calculates a point at fraction value on a line on Earth.

Syntax

geo_line_interpolate_point(lineString,fraction)

Learn more about syntax conventions.

Parameters

Name Type Required Description
lineString dynamic ✔️ A LineString in the GeoJSON format.
fraction real ✔️ fraction value should be between 0 (start of the line) and 1 (end of the line).

Returns

The point coordinate value in GeoJSON Format and of a dynamic data type on line string at the specific fraction value. If the line or fraction value is 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.
  • The input should not contain more than a single line string.
  • In order to calculate a fraction value use geo_line_locate_point()

LineString definition and constraints

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

Examples

The following example calculates a point at 25% location since line start.

Run the query

let line = dynamic({"type":"LineString","coordinates":[[-73.95796, 40.80042], [-73.97317, 40.764486]]});
print point = geo_line_interpolate_point(line, 0.25);

Output

point
{"type": "Point", "coordinates": [-73.961764043218281, 40.791436687257232]}

The following example calculates point longitude at 90% since line start.

Run the query

let line = dynamic({"type":"LineString","coordinates":[[-73.95807266235352,40.800426144169315],[-73.94966125488281,40.79691751000055],[-73.97317886352539,40.764486356930334],[-73.98210525512695,40.76786669510221],[-73.96004676818848,40.7980870753293]]});
print point = geo_line_interpolate_point(line, 0.9)
| project lng = point.coordinates[0]

Output

result
-73.96556545832799

The following example visualizes point on a map.

Run the query

let line = dynamic({"type":"LineString","coordinates":[[-73.95807266235352,40.800426144169315],[-73.94966125488281,40.79691751000055],[-73.97317886352539,40.764486356930334],[-73.98210525512695,40.76786669510221],[-73.96004676818848,40.7980870753293]]});
print point = geo_line_interpolate_point(line, 0.9)
| render scatterchart with (kind = map)

Screenshot of an interpolated point at the New York City Central Park.

The following example returns true because of the invalid line.

Run the query

print is_bad_line = isnull(geo_line_interpolate_point(dynamic({"type":"LineString","coordinates":[[1, 1]]}), 0.5))

Output

is_bad_line
true
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