geo_line_densify()

Learn how to use the geo_line_densify() function to convert planar lines or multiline edges to geodesics.

Converts planar lines or multiline edges to geodesics by adding intermediate points.

Syntax

geo_line_densify(lineString, tolerance, [ preserve_crossing ])

Parameters

NameTypeRequiredDescription
lineStringdynamic✔️A LineString or MultiLineString in the GeoJSON format.
toleranceint, long, or realDefines maximum distance in meters between the original planar edge and the converted geodesic edge chain. Supported values are in the range [0.1, 10000]. If unspecified, the default value 10 is used.
preserve_crossingboolIf true, preserves edge crossing over antimeridian. If unspecified, the default value false is used.

Returns

Densified line in the GeoJSON format and of a dynamic data type. If either the line or tolerance is invalid, the query will produce a null result.

LineString definition

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.
  • The coordinates [longitude, latitude] must be valid. The longitude must be a real number in the range [-180, +180] and the latitude must be a real number in the range [-90, +90].
  • The edge length must be less than 180 degrees. The shortest edge between the two vertices will be chosen.

Constraints

  • The maximum number of points in the densified line is limited to 10485760.
  • Storing lines in dynamic format has size limits.

Motivation

  • GeoJSON format defines an edge between two points as a straight cartesian line while geo_line_densify() uses geodesic.
  • The decision to use geodesic or planar edges might depend on the dataset and is especially relevant in long edges.

Examples

The following example densifies a road in Manhattan island. The edge is short and the distance between the planar edge and its geodesic counterpart is less than the distance specified by tolerance. As such, the result remains unchanged.

print densified_line = tostring(geo_line_densify(dynamic({"type":"LineString","coordinates":[[-73.949247, 40.796860],[-73.973017, 40.764323]]})))

Output

densified_line
{“type”:“LineString”,“coordinates”:[[-73.949247, 40.796860], [-73.973017, 40.764323]]}

The following example densifies an edge of ~130-km length

print densified_line = tostring(geo_line_densify(dynamic({"type":"LineString","coordinates":[[50, 50], [51, 51]]})))

Output

densified_line
{“type”:“LineString”,“coordinates”:[[50,50],[50.125,50.125],[50.25,50.25],[50.375,50.375],[50.5,50.5],[50.625,50.625],[50.75,50.75],[50.875,50.875],[51,51]]}

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

print densified_line = geo_line_densify(dynamic({"type":"LineString","coordinates":[[300,1],[1,1]]}))

Output

densified_line

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

print densified_line = geo_line_densify(dynamic({"type":"LineString","coordinates":[[1,1],[2,2]]}), 0)

Output

densified_line