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A LINESTRING is a collection of Points that are “strung together” into one geometric object. A LineString can be used to represent an arbitrary curve, such as a Bézier curve. In practice, this means that LineStrings are useful for representing real-world objects such as roads and rivers. The coordinates of each Point that makes up the LineString are translated according to the current spatial reference system (denoted by an SRID) to determine what the Point “is”, or what it “means” relative to the other spatial objects (if any) in the data set. You can also store a “ with the following additional dimensions:
  • A third dimension coordinate Z (Z).
  • A measure coordinate M (M).
  • Both a third dimension and a measure coordinate (ZM).
The Z and M dimensions can be accessed or modified using a number of built-in functions, including:
  • ST_Z
  • ST_M
  • ST_Affine
  • ST_Zmflag
  • ST_MakePoint
  • ST_MakePointM
  • ST_Force3D
  • ST_Force3DZ
  • ST_Force3DM
  • ST_Force4D
  • ST_Snap
  • ST_SnapToGrid
  • ST_RotateZ
  • ST_AddMeasure
Note that CockroachDB’s spatial indexing is still based on the 2D coordinate system. This means that:
  • The Z/M dimension is not index accelerated when using spatial predicates.
  • Some spatial functions ignore the Z/M dimension, with transformations discarding the Z/M value.

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Examples

A LineString can be created from SQL by calling the st_geomfromtext function on a LineString definition expressed in the Well Known Text (WKT) format as shown below.
You can also make a LineString using the aggregate function form of st_makeline.

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See also