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    Geospatial Function

    마지막 업데이트 시간:2024-03-20 11:47:49
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      This document introduces the basic syntax and examples of geospatial functions.

      Concepts

      Geospatial functions support Well-Known Text (WKT) and Well-Known Binary (WKB) forms of geometries. For related concepts, see Well-known text representation of geometry - Wikipedia.
      Geometry
      WKT Format
      Point
      POINT (0 0)
      LineString
      LINESTRING (0 0, 1 1, 1 2)
      Polygon
      POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))
      MultiPoint
      MULTIPOINT (0 0, 1 2)
      MultiLineString
      MULTILINESTRING ((0 0, 1 1, 1 2), (2 3, 3 2, 5 4))
      MultiPolygon
      MULTIPOLYGON (((0 0, 4 0, 4 4, 0 4, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), ((-1 -1, -1 -2, -2 -2, -2 -1, -1 -1)))
      GeometryCollection
      GEOMETRYCOLLECTION (POINT(2 3), LINESTRING (2 3, 3 4))
      Geometries default to plane geometries, in which the shortest distance between two points is a straight line. Geometries also support spherical geometries, where the shortest distance between two points is a great circle arc. You can use to_spherical_geography() to convert a plane geometry into a spherical geometry. For example: ST_Distance(ST_Point(-71.0882, 42.3607), ST_Point(-74.1197, 40.6976)) calculates the distance between two points on a plane, and the result is 3.4577. ST_Distance(to_spherical_geography(ST_Point(-71.0882, 42.3607)), to_spherical_geography(ST_Point(-74.1197, 40.6976))) calculates the distance between two points on a sphere, and the result is 312822.179.
      When a length is calculated (for example, ST_Distance() and ST_Length()), the unit is meter. When an area is calculated (for example, ST_Area()), the unit is square meter.

      Constructing a Geometry

      Function
      Return Value Type
      Description
      ST_Point(double, double)
      Point
      Constructs a point.
      ST_LineFromText(varchar)
      LineString
      Constructs a LineString based on WKT text.
      ST_Polygon(varchar)
      Polygon
      Constructs a polygon based on WKT text.
      ST_GeometryFromText(varchar)
      Geometry
      Constructs a geometry based on WKT text.
      ST_GeomFromBinary(varbinary)
      Geometry
      Constructs a geometry based on WKB representation.
      ST_AsText(Geometry)
      varchar
      Converts a geometry into WKT format.
      to_spherical_geography(Geometry)
      SphericalGeography
      Converts a plane geometry into a spherical geometry.
      to_geometry(SphericalGeography)
      Geometry
      Converts a spherical geometry into a plane geometry.

      Relationship Tests

      Function
      Return Value Type
      Description
      ST_Contains(Geometry, Geometry)
      boolean
      Returns true if and only if no points of the second geometry lie in the exterior of the first geometry, and at least one point of the interior of the first geometry lies in the interior of the second geometry. Returns false if the second geometry lies exactly on the boundary of the first geometry.
      ST_Crosses(Geometry, Geometry)
      boolean
      Returns true if the given geometries have some, but not all, interior points in common.
      ST_Disjoint(Geometry, Geometry)
      boolean
      Returns true if the given geometries do not spatially intersect.
      ST_Equals(Geometry, Geometry)
      boolean
      Returns true if the given geometries represent the same geometry.
      ST_Intersects(Geometry, Geometry)
      boolean
      Returns true if the given geometries spatially intersect in two dimensions.
      ST_Overlaps(Geometry, Geometry)
      boolean
      Returns true if the given geometries are of the same dimension, but are not completely contained by each other.
      ST_Relate(Geometry, Geometry)
      boolean
      Returns true if the first geometry is spatially related to the second geometry.
      ST_Touches(Geometry, Geometry)
      boolean
      Returns true if a geometry spatially touches another geometry, but their interiors do not intersect.
      ST_Within(Geometry, Geometry)
      boolean
      Returns true if first geometry is completely inside the second geometry. Return false if their boundaries intersect.

      Operations

      Function
      Return Value Type
      Description
      geometry_nearest_points(Geometry, Geometry)
      row(Point, Point)
      Returns the two closest points between two geometries.
      geometry_union(array(Geometry))
      Geometry
      Combines multiple geometries into one.
      ST_Boundary(Geometry)
      Geometry
      Returns the boundary (closure) of a geometry.
      ST_Buffer(Geometry, distance)
      Geometry
      Returns a geometric object that represents the union of all points whose distance from a geometry is less than or equal to a specified value.
      ST_Difference(Geometry, Geometry)
      Geometry
      Returns the geometry value that represents the point set difference of the two given geometries.
      ST_Envelope(Geometry)
      Geometry
      Returns the bounding rectangular polygon of the geometry.
      ST_ExteriorRing(Geometry)
      Geometry
      Returns the exterior ring of the input polygon.
      ST_Intersection(Geometry, Geometry)
      Geometry
      Returns the geometry value that represents the point set intersection of two given geometries.
      ST_SymDifference(Geometry, Geometry)
      Geometry
      Returns the geometry value that represents the point set symmetric difference of two geometries.

      Accessors

      Function
      Return Value Type
      Description
      ST_Area(Geometry)
      double
      Returns the area of a polygon in a plane geometry.
      ST_Area(SphericalGeography)
      double
      Returns the area of a polygon in a spherical geometry.
      ST_Centroid(Geometry)
      Geometry
      Returns the point value that is the mathematical centroid of a geometry.
      ST_CoordDim(Geometry)
      bigint
      Returns the coordinate dimension of the geometry.
      ST_Dimension(Geometry)
      bigint
      Returns the inherent dimension of this geometry, which must be less than or equal to the coordinate dimension.
      ST_Distance(Geometry, Geometry)
      double
      Returns the minimum distance between two geometries.
      ST_Distance(SphericalGeography, SphericalGeography)
      double
      Returns the smallest distance between two spherical geographies.
      ST_IsClosed(Geometry)
      boolean
      Returns true if the start and end points of the given geometry are the same.
      ST_IsEmpty(Geometry)
      boolean
      Returns true if the geometry is an empty GeometryCollection, polygon, point etc.
      ST_IsRing(Geometry)
      boolean
      Returns true if and only if the geometry is a closed and simple line.
      ST_Length(Geometry)
      double
      Returns the length of a LineString or MultiLineString on a plane geometry.
      ST_Length(SphericalGeography)
      double
      Returns the length of a LineString or MultiLineString on a spherical geometry.
      ST_XMax(Geometry)
      double
      Returns the X maxima of a bounding box of a geometry.
      ST_YMax(Geometry)
      double
      Returns the Y maxima of a bounding box of a geometry.
      ST_XMin(Geometry)
      double
      Returns the X minima of a bounding box of a geometry.
      ST_YMin(Geometry)
      double
      Returns the Y minima of a bounding box of a geometry.
      ST_StartPoint(Geometry)
      point
      Returns the first point of a LineString geometry.
      ST_EndPoint(Geometry)
      point
      Returns the last point of a LineString geometry.
      ST_X(Point)
      double
      Returns the X coordinate of the point.
      ST_Y(Point)
      double
      Returns the Y coordinate of the point.
      ST_NumPoints(Geometry)
      bigint
      Returns the number of points in a geometry.
      ST_NumInteriorRing(Geometry)
      bigint
      Returns the number of the interior rings of a polygon.
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