Geography Functions

The Geography type in WherobotsDB represents spatial objects on a spherical (geodesic) model of the Earth. Unlike the planar Geometry type, distance, area, and other measurements performed on Geography objects account for the curvature of the Earth and return results in real-world units (e.g., meters).

Geography Constructors

These functions create geography objects from various formats.

Function	Return type	Description
ST_GeogCollFromText	Geography	Constructs a Geography Collection from a WKT (Well-Known Text) string. If SRID is not set, it defaults to 0 (unknown).
ST_GeogFromEWKB	Geography	Construct a Geography from EWKB Binary. This function is an alias of ST_GeogFromWKB.
ST_GeogFromEWKT	Geography	Construct a Geography from OGC Extended WKT.
ST_GeogFromGeoHash	Geography	Create Geography from geohash string and optional precision
ST_GeogFromText	Geography	Constructs a Geography object from a WKT (Well-Known Text) string. If SRID is not set, it defaults to 0 (unknown).
ST_GeogFromWKB	Geography	Construct a Geography from WKB Binary.
ST_GeogFromWKT	Geography	Construct a Geography from WKT. If SRID is not set, it defaults to 0 (unknown).
ST_GeogToGeometry	Geometry	This function constructs a planar Geometry object from a Geography. While WherobotsDB makes every effort to preserve the original spatial object, the conversion is not always exact because Geography and…
ST_GeomToGeography	Geography	This function constructs a Geography object from a planar Geometry. This function is intended for geometries defined in a Geographic Coordinate Reference System (CRS), most commonly WGS84 (EPSG:432…
ST_MakeLine	Geography	Create a Geography LineString from two supported geographies.

Geography Accessors and Output

These functions return properties of geography objects or convert them to text.

Function	Return type	Description
ST_AsEWKT	String	Return the Extended Well-Known Text representation of a geography. EWKT is an extended version of WKT which includes the SRID of the geography. The format originated in PostGIS but is supported by …
ST_AsText	String	Well-Known Text (WKT) representation of a geography.
ST_GeometryType	String	Type of a geography as a string (e.g., `ST_Point`).
ST_NPoints	Integer	Number of points (vertices) in a geography.
ST_NumGeometries	Integer	Number of sub-geometries in a geography (1 for single geometries).
ST_X	Double	Longitude of a point geography.
ST_Y	Double	Latitude of a point geography.

Geography Predicates

These functions test spatial relationships between geographies, returning boolean values.

Function	Return type	Description
ST_Contains	Boolean	Test whether geography A fully contains geography B.
ST_DWithin	Boolean	Test whether two geographies are within a given geodesic distance (in meters).
ST_Equals	Boolean	Test whether two geographies are spatially equal.
ST_Intersects	Boolean	Test whether two geographies intersect.
ST_Within	Boolean	Test whether geography A is fully within geography B.

Geography Measurement

These functions compute geodesic distance, area, and length, in meters.

Function	Return type	Description
ST_Area	Double	Spherical area of a geography, in square meters.
ST_Distance	Double	Minimum geodesic distance between two geographies, in meters.
ST_Length	Double	Spherical length of a geography, in meters.

Geography Processing

These functions compute new geographies from existing ones.

Function	Return type	Description
ST_Buffer	Geography	Metric ε-buffer of a geography (distance in meters along the spheroid).
ST_Centroid	Geography	Spherical centroid of a geography, as a Geography point.
ST_Envelope	Geography	This function returns the bounding box (envelope) of A. It’s important to note that the bounding box is calculated using a cylindrical topology, not a spherical one. If the envelope crosses the ant…
ST_Intersection	Geography	Closed-set spherical intersection of two geographies.

​Geography Constructors

​Geography Accessors and Output

​Geography Predicates

​Geography Measurement

​Geography Processing

Geography Constructors

Geography Accessors and Output

Geography Predicates

Geography Measurement

Geography Processing