41. 附录 A：PostGIS 函数¶

41.1. 构造器¶

ST_MakePoint(Longitude, Latitude): 返回一个新的点。注意坐标分量的顺序（先经度，然后纬度）。
ST_GeomFromText(WellKnownText, srid): 输入 WKT 字符串和 srid 并返回一个新的几何对象。
ST_SetSRID(geometry, srid): Updates the srid on a geometry. Returns the same geometry. This does not alter the coordinates of the geometry, it just updates the srid. This function is useful for conditioning geometries created without an srid.
ST_Expand(geometry, Radius): Returns a new geometry that is an expanded bounding box of the input geometry. This function is useful for creating envelopes for use in indexed searches.

ST_Area(geometry): 返回基于坐标系单位的几何对象的面积。
ST_Length(geometry): Returns the length of the geometry in the units of the spatial reference system.
ST_Perimeter(geometry): Returns the perimeter of the geometry in the units of the spatial reference system.
ST_NumPoints(linestring): Returns the number of vertices in a linestring.
ST_NumRings(polygon): 返回 Polygon 中 Ring 的数量。
ST_NumGeometries(geometry): 返回几何容器（GeometryCollection）中几何对象的个数。

ST_Distance(geometry, geometry): Returns the distance between two geometries in the units of the spatial reference system.
ST_DWithin(geometry, geometry, radius): Returns true if the geometries are within the radius distance of one another, otherwise false.
ST_Intersects(geometry, geometry): Returns true if the geometries are not disjoint, otherwise false.
ST_Contains(geometry, geometry): Returns true if the first geometry fully contains the second geometry, otherwise false.
ST_Crosses(geometry, geometry): Returns true if a line or polygon boundary crosses another line or polygon boundary, otherwise false.