GeometryType Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc. text GeometryType geometry geomA Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc. OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member. The name of the instantiable subtype of Geometry is returned as a string. This function also indicates if the geometry is measured, by returning a string of the form 'POINTM'. Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. &sfs_compliant; &curve_support; &Z_support; &P_support; &T_support; SELECT GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')); geometrytype -------------- LINESTRING SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')); --result POLYHEDRALSURFACE SELECT GeometryType(geom) as result FROM (SELECT ST_GeomFromEWKT('TIN ((( 0 0 0, 0 0 1, 0 1 0, 0 0 0 )), (( 0 0 0, 0 1 0, 1 1 0, 0 0 0 )) )') AS geom ) AS g; result -------- TIN ST_Boundary Returns the closure of the combinatorial boundary of this Geometry. geometry ST_Boundary geometry geomA Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2. Performed by the GEOS module Prior to 2.0.0, this function throws an exception if used with GEOMETRYCOLLECTION. From 2.0.0 up it will return NULL instead (unsupported input). &sfs_compliant; OGC SPEC s2.1.1.1 &sqlmm_compliant; SQL-MM 3: 5.1.14 &Z_support; SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)'))); st_astext ----------- MULTIPOINT(1 1,-1 1) SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))'))); st_astext ---------- LINESTRING(1 1,0 0,-1 1,1 1) --Using a 3d polygon SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))'))); st_asewkt ----------------------------------- LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1) --Using a 3d multilinestring SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )'))); st_asewkt ---------- MULTIPOINT(-1 1 1,1 1 0.75) , ST_CoordDim Return the coordinate dimension of the ST_Geometry value. integer ST_CoordDim geometry geomA Return the coordinate dimension of the ST_Geometry value. This is the MM compliant alias name for &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 5.1.3 &curve_support; &Z_support; &P_support; &T_support; SELECT ST_CoordDim('CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)'); ---result-- 3 SELECT ST_CoordDim(ST_Point(1,2)); --result-- 2 ST_Dimension The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. integer ST_Dimension geometry g The inherent dimension of this Geometry object, which must be less than or equal to the coordinate dimension. OGC SPEC s2.1.1.1 - returns 0 for POINT, 1 for LINESTRING, 2 for POLYGON, and the largest dimension of the components of a GEOMETRYCOLLECTION. If unknown (empty geometry) null is returned. &sqlmm_compliant; SQL-MM 3: 5.1.2 Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry. Prior to 2.0.0, this function throws an exception if used with empty geometry. &P_support; &T_support; SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))'); ST_Dimension ----------- 1 ST_EndPoint Returns the last point of a LINESTRING geometry as a POINT. boolean ST_EndPoint geometry g Returns the last point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING. &sqlmm_compliant; SQL-MM 3: 7.1.4 &Z_support; Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now. postgis=# SELECT ST_AsText(ST_EndPoint('LINESTRING(1 1, 2 2, 3 3)'::geometry)); st_astext ------------ POINT(3 3) (1 row) postgis=# SELECT ST_EndPoint('POINT(1 1)'::geometry) IS NULL AS is_null; is_null ---------- t (1 row) --3d endpoint SELECT ST_AsEWKT(ST_EndPoint('LINESTRING(1 1 2, 1 2 3, 0 0 5)')); st_asewkt -------------- POINT(0 0 5) (1 row) , ST_Envelope Returns a geometry representing the double precision (float8) bounding box of the supplied geometry. geometry ST_Envelope geometry g1 Returns the float8 minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the corner points of the bounding box ((MINX, MINY), (MINX, MAXY), (MAXX, MAXY), (MAXX, MINY), (MINX, MINY)). (PostGIS will add a ZMIN/ZMAX coordinate as well). Degenerate cases (vertical lines, points) will return a geometry of lower dimension than POLYGON, ie. POINT or LINESTRING. Availability: 1.5.0 behavior changed to output double precision instead of float4 &sfs_compliant; s2.1.1.1 &sqlmm_compliant; SQL-MM 3: 5.1.15 SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry)); st_astext ------------ POINT(1 3) (1 row) SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry)); st_astext -------------------------------- POLYGON((0 0,0 3,1 3,1 0,0 0)) (1 row) SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry)); st_astext -------------------------------------------------------------- POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0)) (1 row) SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry)); st_astext -------------------------------------------------------------- POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0)) (1 row) SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewkt FROM (SELECT 'POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))'::geometry As geom) As foo; , ST_ExteriorRing Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Will not work with MULTIPOLYGON geometry ST_ExteriorRing geometry a_polygon Returns a line string representing the exterior ring of the POLYGON geometry. Return NULL if the geometry is not a polygon. Only works with POLYGON geometry types &sfs_compliant; 2.1.5.1 &sqlmm_compliant; SQL-MM 3: 8.2.3, 8.3.3 &Z_support; --If you have a table of polygons SELECT gid, ST_ExteriorRing(the_geom) AS ering FROM sometable; --If you have a table of MULTIPOLYGONs --and want to return a MULTILINESTRING composed of the exterior rings of each polygon SELECT gid, ST_Collect(ST_ExteriorRing(the_geom)) AS erings FROM (SELECT gid, (ST_Dump(the_geom)).geom As the_geom FROM sometable) As foo GROUP BY gid; --3d Example SELECT ST_AsEWKT( ST_ExteriorRing( ST_GeomFromEWKT('POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))') ) ); st_asewkt --------- LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1) , , ST_GeometryN Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL. geometry ST_GeometryN geometry geomA integer n Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead. If you want to extract all geometries, of a geometry, ST_Dump is more efficient and will also work for singular geoms. Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case. &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 9.1.5 &Z_support; &curve_support; &P_support; &T_support; --Extracting a subset of points from a 3d multipoint SELECT n, ST_AsEWKT(ST_GeometryN(the_geom, n)) As geomewkt FROM ( VALUES (ST_GeomFromEWKT('MULTIPOINT(1 2 7, 3 4 7, 5 6 7, 8 9 10)') ), ( ST_GeomFromEWKT('MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))') ) )As foo(the_geom) CROSS JOIN generate_series(1,100) n WHERE n <= ST_NumGeometries(the_geom); n | geomewkt ---+----------------------------------------- 1 | POINT(1 2 7) 2 | POINT(3 4 7) 3 | POINT(5 6 7) 4 | POINT(8 9 10) 1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5) 2 | LINESTRING(10 11,12 11) --Extracting all geometries (useful when you want to assign an id) SELECT gid, n, ST_GeometryN(the_geom, n) FROM sometable CROSS JOIN generate_series(1,100) n WHERE n <= ST_NumGeometries(the_geom); -- Polyhedral surface example -- Break a Polyhedral surface into its faces SELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt FROM (SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )') AS p_geom ) AS a; geom_ewkt ------------------------------------------ POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)) -- TIN -- SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt FROM (SELECT ST_GeomFromEWKT('TIN ((( 0 0 0, 0 0 1, 0 1 0, 0 0 0 )), (( 0 0 0, 0 1 0, 1 1 0, 0 0 0 )) )') AS geom ) AS g; -- result -- wkt ------------------------------------- TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0)) , ST_GeometryType Return the geometry type of the ST_Geometry value. text ST_GeometryType geometry g1 Returns the type of the geometry as a string. EG: 'ST_Linestring', 'ST_Polygon','ST_MultiPolygon' etc. This function differs from GeometryType(geometry) in the case of the string and ST in front that is returned, as well as the fact that it will not indicate whether the geometry is measured. Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. &sqlmm_compliant; SQL-MM 3: 5.1.4 &Z_support; &P_support; SELECT ST_GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')); --result ST_LineString SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')); --result ST_PolyhedralSurface SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')); --result ST_PolyhedralSurface SELECT ST_GeometryType(geom) as result FROM (SELECT ST_GeomFromEWKT('TIN ((( 0 0 0, 0 0 1, 0 1 0, 0 0 0 )), (( 0 0 0, 0 1 0, 1 1 0, 0 0 0 )) )') AS geom ) AS g; result -------- ST_Tin ST_InteriorRingN Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range. geometry ST_InteriorRingN geometry a_polygon integer n Return the Nth interior linestring ring of the polygon geometry. Return NULL if the geometry is not a polygon or the given N is out of range. index starts at 1. This will not work for MULTIPOLYGONs. Use in conjunction with ST_Dump for MULTIPOLYGONS &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 8.2.6, 8.3.5 &Z_support; SELECT ST_AsText(ST_InteriorRingN(the_geom, 1)) As the_geom FROM (SELECT ST_BuildArea( ST_Collect(ST_Buffer(ST_Point(1,2), 20,3), ST_Buffer(ST_Point(1, 2), 10,3))) As the_geom ) as foo , , , , ST_IsClosed Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral surface is closed (volumetric). boolean ST_IsClosed geometry g Returns TRUE if the LINESTRING's start and end points are coincident. For Polyhedral Surfaces, it tells you if the surface is areal (open) or volumetric (closed). &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 7.1.5, 9.3.3 SQL-MM defines the result of ST_IsClosed(NULL) to be 0, while PostGIS returns NULL. &Z_support; &curve_support; Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. &P_support; postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 1 1)'::geometry); st_isclosed ------------- f (1 row) postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 0 1, 1 1, 0 0)'::geometry); st_isclosed ------------- t (1 row) postgis=# SELECT ST_IsClosed('MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))'::geometry); st_isclosed ------------- f (1 row) postgis=# SELECT ST_IsClosed('POINT(0 0)'::geometry); st_isclosed ------------- t (1 row) postgis=# SELECT ST_IsClosed('MULTIPOINT((0 0), (1 1))'::geometry); st_isclosed ------------- t (1 row) -- A cube -- SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')); st_isclosed ------------- t -- Same as cube but missing a side -- SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )')); st_isclosed ------------- f ST_IsCollection Returns TRUE if the argument is a collection (MULTI*, GEOMETRYCOLLECTION, ...) boolean ST_IsCollection geometry g Returns TRUE if the geometry type of the argument is either: GEOMETRYCOLLECTION MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE} COMPOUNDCURVE This function analyzes the type of the geometry. This means that it will return TRUE on collections that are empty or that contain a single element. &Z_support; &curve_support; postgis=# SELECT ST_IsCollection('LINESTRING(0 0, 1 1)'::geometry); st_iscollection ------------- f (1 row) postgis=# SELECT ST_IsCollection('MULTIPOINT EMPTY'::geometry); st_iscollection ------------- t (1 row) postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0))'::geometry); st_iscollection ------------- t (1 row) postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'::geometry); st_iscollection ------------- t (1 row) postgis=# SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'::geometry); st_iscollection ------------- t (1 row) ST_IsEmpty Returns true if this Geometry is an empty geometrycollection, polygon, point etc. boolean ST_IsEmpty geometry geomA Returns true if this Geometry is an empty geometry. If true, then this Geometry represents an empty geometry collection, polygon, point etc. SQL-MM defines the result of ST_IsEmpty(NULL) to be 0, while PostGIS returns NULL. &sfs_compliant; s2.1.1.1 &sqlmm_compliant; SQL-MM 3: 5.1.7 &curve_support; Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards SELECT ST_IsEmpty(ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')); st_isempty ------------ t (1 row) SELECT ST_IsEmpty(ST_GeomFromText('POLYGON EMPTY')); st_isempty ------------ t (1 row) SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')); st_isempty ------------ f (1 row) SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')) = false; ?column? ---------- t (1 row) SELECT ST_IsEmpty(ST_GeomFromText('CIRCULARSTRING EMPTY')); st_isempty ------------ t (1 row) ST_IsRing Returns TRUE if this LINESTRING is both closed and simple. boolean ST_IsRing geometry g Returns TRUE if this LINESTRING is both (ST_StartPoint(g) ~= ST_Endpoint(g)) and (does not self intersect). &sfs_compliant; 2.1.5.1 &sqlmm_compliant; SQL-MM 3: 7.1.6 SQL-MM defines the result of ST_IsRing(NULL) to be 0, while PostGIS returns NULL. SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom) FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS the_geom) AS foo; st_isring | st_isclosed | st_issimple -----------+-------------+------------- t | t | t (1 row) SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom) FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS the_geom) AS foo; st_isring | st_isclosed | st_issimple -----------+-------------+------------- f | t | f (1 row) , , , ST_IsSimple Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency. boolean ST_IsSimple geometry geomA Returns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries" SQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL. &sfs_compliant; s2.1.1.1 &sqlmm_compliant; SQL-MM 3: 5.1.8 &Z_support; SELECT ST_IsSimple(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')); st_issimple ------------- t (1 row) SELECT ST_IsSimple(ST_GeomFromText('LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)')); st_issimple ------------- f (1 row) ST_IsValid Returns true if the ST_Geometry is well formed. boolean ST_IsValid geometry g boolean ST_IsValid geometry g integer flags Test if an ST_Geometry value is well formed. For geometries that are invalid, the PostgreSQL NOTICE will provide details of why it is not valid. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries" SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL. The version accepting flags is available starting with 2.0.0 and requires GEOS >= 3.3.0. Such version does not print a NOTICE explaining the invalidity. Allowed flags are documented in . &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 5.1.9 SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line, ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly --results NOTICE: Self-intersection at or near point 0 0 good_line | bad_poly -----------+---------- t | f , , , ST_IsValidReason Returns text stating if a geometry is valid or not and if not valid, a reason why. text ST_IsValidReason geometry geomA text ST_IsValidReason geometry geomA integer flags Returns text stating if a geometry is valid or not an if not valid, a reason why. Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons. Allowed flags are documented in . Availability: 1.4 - requires GEOS >= 3.1.0. Availability: 2.0 - requires GEOS >= 3.3.0 for the version taking flags. --First 3 Rejects from a successful quintuplet experiment SELECT gid, ST_IsValidReason(the_geom) as validity_info FROM (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid FROM generate_series(-4,6) x1 CROSS JOIN generate_series(2,5) y1 CROSS JOIN generate_series(1,8) z1 WHERE x1 > y1*0.5 AND z1 < x1*y1) As e INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line FROM generate_series(-3,6) x1 CROSS JOIN generate_series(2,5) y1 CROSS JOIN generate_series(1,10) z1 WHERE x1 > y1*0.75 AND z1 < x1*y1) As f ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line)) GROUP BY gid, e.buff) As quintuplet_experiment WHERE ST_IsValid(the_geom) = false ORDER BY gid LIMIT 3; gid | validity_info ------+-------------------------- 5330 | Self-intersection [32 5] 5340 | Self-intersection [42 5] 5350 | Self-intersection [52 5] --simple example SELECT ST_IsValidReason('LINESTRING(220227 150406,2220227 150407,222020 150410)'); st_isvalidreason ------------------ Valid Geometry , ST_IsValidDetail Returns a valid_detail (valid,reason,location) row stating if a geometry is valid or not and if not valid, a reason why and a location where. valid_detail ST_IsValidDetail geometry geom valid_detail ST_IsValidDetail geometry geom integer flags Returns a valid_detail row, formed by a boolean (valid) stating if a geometry is valid, a varchar (reason) stating a reason why it is invalid and a geometry (location) pointing out where it is invalid. Useful to substitute and improve the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalid geometries. The 'flags' argument is a bitfield. It can have the following values: 1: Consider self-intersecting rings forming holes as valid. This is also know as "the ESRI flag". Note that this is against the OGC model. Availability: 2.0.0 - requires GEOS >= 3.3.0. --First 3 Rejects from a successful quintuplet experiment SELECT gid, reason(ST_IsValidDetail(the_geom)), ST_AsText(location(ST_IsValidDetail(the_geom))) as location FROM (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), ST_Accum(f.line)) As the_geom, gid FROM (SELECT ST_Buffer(ST_MakePoint(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid FROM generate_series(-4,6) x1 CROSS JOIN generate_series(2,5) y1 CROSS JOIN generate_series(1,8) z1 WHERE x1 > y1*0.5 AND z1 < x1*y1) As e INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_MakePoint(x1*10,y1), z1)),y1*1, z1*2) As line FROM generate_series(-3,6) x1 CROSS JOIN generate_series(2,5) y1 CROSS JOIN generate_series(1,10) z1 WHERE x1 > y1*0.75 AND z1 < x1*y1) As f ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line)) GROUP BY gid, e.buff) As quintuplet_experiment WHERE ST_IsValid(the_geom) = false ORDER BY gid LIMIT 3; gid | reason | location ------+-------------------+------------- 5330 | Self-intersection | POINT(32 5) 5340 | Self-intersection | POINT(42 5) 5350 | Self-intersection | POINT(52 5) --simple example SELECT * FROM ST_IsValidDetail('LINESTRING(220227 150406,2220227 150407,222020 150410)'); valid | reason | location -------+--------+---------- t | | , ST_M Return the M coordinate of the point, or NULL if not available. Input must be a point. float ST_M geometry a_point Return the M coordinate of the point, or NULL if not available. Input must be a point. This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list. &sfs_compliant; &sqlmm_compliant; &Z_support; SELECT ST_M(ST_GeomFromEWKT('POINT(1 2 3 4)')); st_m ------ 4 (1 row) , , , ST_NDims Returns coordinate dimension of the geometry as a small int. Values are: 2,3 or 4. integer ST_NDims geometry g1 Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3D with measure space x,y,z,m &Z_support; SELECT ST_NDims(ST_GeomFromText('POINT(1 1)')) As d2point, ST_NDims(ST_GeomFromEWKT('POINT(1 1 2)')) As d3point, ST_NDims(ST_GeomFromEWKT('POINTM(1 1 0.5)')) As d2pointm; d2point | d3point | d2pointm ---------+---------+---------- 2 | 3 | 3 , , ST_NPoints Return the number of points (vertexes) in a geometry. integer ST_NPoints geometry g1 Return the number of points in a geometry. Works for all geometries. Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+ &Z_support; &curve_support; &P_support; SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')); --result 4 --Polygon in 3D space SELECT ST_NPoints(ST_GeomFromEWKT('LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 -1,77.29 29.07 3)')) --result 4 ST_NRings If the geometry is a polygon or multi-polygon returns the number of rings. integer ST_NRings geometry geomA If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings as well. &Z_support; &curve_support; SELECT ST_NRings(the_geom) As Nrings, ST_NumInteriorRings(the_geom) As ninterrings FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As the_geom) As foo; nrings | ninterrings --------+------------- 1 | 0 (1 row) ST_NumGeometries If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL. integer ST_NumGeometries geometry geom Returns the number of Geometries. If geometry is a GEOMETRYCOLLECTION (or MULTI*) return the number of geometries, for single geometries will return 1, otherwise return NULL. Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT. &sqlmm_compliant; SQL-MM 3: 9.1.4 &Z_support; &P_support; &T_support; --Prior versions would have returned NULL for this -- in 2.0.0 this returns 1 SELECT ST_NumGeometries(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')); --result 1 --Geometry Collection Example - multis count as one geom in a collection SELECT ST_NumGeometries(ST_GeomFromEWKT('GEOMETRYCOLLECTION(MULTIPOINT(-2 3 , -2 2), LINESTRING(5 5 ,10 10), POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))')); --result 3 , ST_NumInteriorRings Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry. integer ST_NumInteriorRings geometry a_polygon Return the number of interior rings of the first polygon in the geometry. This will work with both POLYGON and MULTIPOLYGON types but only looks at the first polygon. Return NULL if there is no polygon in the geometry. &sqlmm_compliant; SQL-MM 3: 8.2.5 --If you have a regular polygon SELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholes FROM sometable; --If you have multipolygons --And you want to know the total number of interior rings in the MULTIPOLYGON SELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholes FROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom FROM sometable) As foo GROUP BY gid, field1,field2; ST_NumInteriorRing Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings. integer ST_NumInteriorRing geometry a_polygon Return the number of interior rings of the first polygon in the geometry. Synonym to ST_NumInteriorRings. The OpenGIS specs are ambiguous about the exact function naming, so we provide both spellings. &sqlmm_compliant; SQL-MM 3: 8.2.5 ST_NumPatches Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. integer ST_NumPatches geometry g1 Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias for ST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don't care about MM convention. Availability: 2.0.0 &Z_support; &sfs_compliant; &sqlmm_compliant; SQL-MM 3: ? &P_support; SELECT ST_NumPatches(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')); --result 6 , ST_NumPoints Return the number of points in an ST_LineString or ST_CircularString value. integer ST_NumPoints geometry g1 Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with Linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just line strings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types. &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 7.2.4 SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')); --result 4 ST_PatchN Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL. geometry ST_PatchN geometry geomA integer n >Return the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE, POLYHEDRALSURFACEM. Otherwise, return NULL. This returns the same answer as ST_GeometryN for Polyhedral Surfaces. Using ST_GemoetryN is faster. Index is 1-based. If you want to extract all geometries, of a geometry, ST_Dump is more efficient. Availability: 2.0.0 &sqlmm_compliant; SQL-MM 3: ? &Z_support; &P_support; --Extract the 2nd face of the polyhedral surface SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt FROM ( VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom); geomewkt ---+----------------------------------------- POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)) , , , , ST_PointN Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry. geometry ST_PointN geometry a_linestring integer n Return the Nth point in the first linestring or circular linestring in the geometry. Return NULL if there is no linestring in the geometry. Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead. If you want to get the nth point of each line string in a multilinestring, use in conjunction with ST_Dump &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 7.2.5, 7.3.5 &Z_support; &curve_support; -- Extract all POINTs from a LINESTRING SELECT ST_AsText( ST_PointN( column1, generate_series(1, ST_NPoints(column1)) )) FROM ( VALUES ('LINESTRING(0 0, 1 1, 2 2)'::geometry) ) AS foo; st_astext ------------ POINT(0 0) POINT(1 1) POINT(2 2) (3 rows) --Example circular string SELECT ST_AsText(ST_PointN(ST_GeomFromText('CIRCULARSTRING(1 2, 3 2, 1 2)'),2)); st_astext ---------- POINT(3 2) ST_SRID Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. integer ST_SRID geometry g1 Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries. &sfs_compliant; s2.1.1.1 &sqlmm_compliant; SQL-MM 3: 5.1.5 &curve_support; SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326)); --result 4326 , , , ST_StartPoint Returns the first point of a LINESTRING geometry as a POINT. geometry ST_StartPoint geometry geomA Returns the first point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING. &sqlmm_compliant; SQL-MM 3: 7.1.3 &Z_support; Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now. SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry)); st_astext ------------ POINT(0 1) (1 row) SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null; is_null ---------- t (1 row) --3d line SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry)); st_asewkt ------------ POINT(0 1 1) (1 row) , ST_Summary Returns a text summary of the contents of the geometry. text ST_Summary geometry g text ST_Summary geography g Returns a text summary of the contents of the geometry. Flags shown square brackets after the geometry type have the following meaning: M: has M ordinate Z: has Z ordinate B: has a cached bounding box G: is geodetic (geography) Availability: 1.2.2 - 2.0.0 added support for geography =# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom, ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog; geom | geog -----------------------------+-------------------------- LineString[B] with 2 points | Polygon[BG] with 1 rings : ring 0 has 5 points : (1 row) =# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line, ST_Summary(ST_GeomFromText('POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly; ; geog_line | geom_poly -------------------------------+-------------------------- LineString[ZBG] with 2 points | Polygon[ZB] with 1 rings : ring 0 has 5 points : (1 row) , , , , , , , , ST_X Return the X coordinate of the point, or NULL if not available. Input must be a point. float ST_X geometry a_point Return the X coordinate of the point, or NULL if not available. Input must be a point. If you want to get the max min x values of any geometry look at ST_XMin, ST_XMax functions. &sqlmm_compliant; SQL-MM 3: 6.1.3 &Z_support; SELECT ST_X(ST_GeomFromEWKT('POINT(1 2 3 4)')); st_x ------ 1 (1 row) SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)'))); st_y ------ 1.5 (1 row) , , , , , , ST_XMax Returns X maxima of a bounding box 2d or 3d or a geometry. float ST_XMax box3d aGeomorBox2DorBox3D Returns X maxima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_XMax('BOX3D(1 2 3, 4 5 6)'); st_xmax ------- 4 SELECT ST_XMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)')); st_xmax ------- 5 SELECT ST_XMax(CAST('BOX(-3 2, 3 4)' As box2d)); st_xmax ------- 3 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_XMax('LINESTRING(1 3, 5 6)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_XMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_xmax -------- 220288.248780547 , , , , ST_XMin Returns X minima of a bounding box 2d or 3d or a geometry. float ST_XMin box3d aGeomorBox2DorBox3D Returns X minima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_XMin('BOX3D(1 2 3, 4 5 6)'); st_xmin ------- 1 SELECT ST_XMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)')); st_xmin ------- 1 SELECT ST_XMin(CAST('BOX(-3 2, 3 4)' As box2d)); st_xmin ------- -3 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_XMin('LINESTRING(1 3, 5 6)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_XMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_xmin -------- 220186.995121892 , , , , ST_Y Return the Y coordinate of the point, or NULL if not available. Input must be a point. float ST_Y geometry a_point Return the Y coordinate of the point, or NULL if not available. Input must be a point. &sfs_compliant; &sqlmm_compliant; SQL-MM 3: 6.1.4 &Z_support; SELECT ST_Y(ST_GeomFromEWKT('POINT(1 2 3 4)')); st_y ------ 2 (1 row) SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)'))); st_y ------ 1.5 (1 row) , , , , , , ST_YMax Returns Y maxima of a bounding box 2d or 3d or a geometry. float ST_YMax box3d aGeomorBox2DorBox3D Returns Y maxima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_YMax('BOX3D(1 2 3, 4 5 6)'); st_ymax ------- 5 SELECT ST_YMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)')); st_ymax ------- 6 SELECT ST_YMax(CAST('BOX(-3 2, 3 4)' As box2d)); st_ymax ------- 4 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_YMax('LINESTRING(1 3, 5 6)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_YMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_ymax -------- 150506.126829327 , , , , ST_YMin Returns Y minima of a bounding box 2d or 3d or a geometry. float ST_YMin box3d aGeomorBox2DorBox3D Returns Y minima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_YMin('BOX3D(1 2 3, 4 5 6)'); st_ymin ------- 2 SELECT ST_YMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)')); st_ymin ------- 3 SELECT ST_YMin(CAST('BOX(-3 2, 3 4)' As box2d)); st_ymin ------- 2 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_YMin('LINESTRING(1 3, 5 6)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_YMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_ymin -------- 150406 , , , , , ST_Z Return the Z coordinate of the point, or NULL if not available. Input must be a point. float ST_Z geometry a_point Return the Z coordinate of the point, or NULL if not available. Input must be a point. &sqlmm_compliant; &Z_support; SELECT ST_Z(ST_GeomFromEWKT('POINT(1 2 3 4)')); st_z ------ 3 (1 row) , , , , , ST_ZMax Returns Z minima of a bounding box 2d or 3d or a geometry. float ST_ZMax box3d aGeomorBox2DorBox3D Returns Z maxima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_ZMax('BOX3D(1 2 3, 4 5 6)'); st_zmax ------- 6 SELECT ST_ZMax(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)')); st_zmax ------- 7 SELECT ST_ZMax('BOX3D(-3 2 1, 3 4 1)' ); st_zmax ------- 1 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_ZMax('LINESTRING(1 3 4, 5 6 7)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_ZMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_zmax -------- 3 , , , , , ST_Zmflag Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d. smallint ST_Zmflag geometry geomA Returns ZM (dimension semantic) flag of the geometries as a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d. &Z_support; &curve_support; SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRING(1 2, 3 4)')); st_zmflag ----------- 0 SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRINGM(1 2 3, 3 4 3)')); st_zmflag ----------- 1 SELECT ST_Zmflag(ST_GeomFromEWKT('CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)')); st_zmflag ----------- 2 SELECT ST_Zmflag(ST_GeomFromEWKT('POINT(1 2 3 4)')); st_zmflag ----------- 3 , , ST_ZMin Returns Z minima of a bounding box 2d or 3d or a geometry. float ST_ZMin box3d aGeomorBox2DorBox3D Returns Z minima of a bounding box 2d or 3d or a geometry. Although this function is only defined for box3d, it will work for box2d and geometry because of the auto-casting behavior defined for geometries and box2d. However you can not feed it a geometry or box2d text representation, since that will not auto-cast. &Z_support; &curve_support; SELECT ST_ZMin('BOX3D(1 2 3, 4 5 6)'); st_zmin ------- 3 SELECT ST_ZMin(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)')); st_zmin ------- 4 SELECT ST_ZMin('BOX3D(-3 2 1, 3 4 1)' ); st_zmin ------- 1 --Observe THIS DOES NOT WORK because it will try to autocast the string representation to a BOX3D SELECT ST_ZMin('LINESTRING(1 3 4, 5 6 7)'); --ERROR: BOX3D parser - doesnt start with BOX3D( SELECT ST_ZMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')); st_zmin -------- 1 , , , , , ,