# Geometry Editors

ST_AddPoint

Add a point to a LineString.

    				geometry ST_AddPoint
    				geometry linestring
    				geometry point

    				geometry ST_AddPoint
    				geometry linestring
    				geometry point
    				integer position

### Description

Adds a point to a LineString before point <position> (0-based index). Third parameter can be omitted or set to -1 for appending.

Availability: 1.1.0

&Z_support;

### Examples

    		--guarantee all linestrings in a table are closed
    		--by adding the start point of each linestring to the end of the line string
    		--only for those that are not closed
    		UPDATE sometable
    		SET the_geom = ST_AddPoint(the_geom, ST_StartPoint(the_geom))
    		FROM sometable
    		WHERE ST_IsClosed(the_geom) = false;

    		--Adding point to a 3-d line
    		SELECT ST_AsEWKT(ST_AddPoint(ST_GeomFromEWKT('LINESTRING(0 0 1, 1 1 1)'), ST_MakePoint(1, 2, 3)));

    		--result
    		st_asewkt
    		----------
    		LINESTRING(0 0 1,1 1 1,1 2 3)

### See Also

ST_RemovePoint, ST_SetPoint

ST_CollectionExtract

Given a (multi)geometry, return a (multi)geometry consisting only of elements of the specified type.

    				geometry ST_CollectionExtract
    				geometry  collection
    				integer  type

### Description

Given a (multi)geometry, returns a (multi)geometry consisting only of elements of the specified type. Sub-geometries that are not the specified type are ignored. If there are no sub-geometries of the right type, an EMPTY geometry will be returned. Only points, lines and polygons are supported. Type numbers are 1 == POINT, 2 == LINESTRING, 3 == POLYGON.

Availability: 1.5.0

Prior to 1.5.3 this function returned non-collection inputs untouched, no matter type. In 1.5.3 non-matching single geometries result in a NULL return. In of 2.0.0 every case of missing match results in a typed EMPTY return.

When specifying 3 == POLYGON a multipolygon is returned even when the edges are shared. This results in an invalid multipolygon for many cases such as applying this function on an ST_Split result.

### Examples

    -- Constants: 1 == POINT, 2 == LINESTRING, 3 == POLYGON
    SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(POINT(0 0)))'),1));
    st_astext
    ---------------
    MULTIPOINT(0 0)
    (1 row)

    SELECT ST_AsText(ST_CollectionExtract(ST_GeomFromText('GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))'),2));
    st_astext
    ---------------
    MULTILINESTRING((0 0, 1 1), (2 2, 3 3))
    (1 row)

### See Also

ST_Multi, ST_Dump, ST_CollectionHomogenize

ST_CollectionHomogenize

Given a geometry collection, return the "simplest" representation of the contents.

    					geometry ST_CollectionHomogenize
    					geometry  collection

### Description

Given a geometry collection, returns the "simplest" representation of the contents. Singletons will be returned as singletons. Collections that are homogeneous will be returned as the appropriate multi-type.

When specifying 3 == POLYGON a multipolygon is returned even when the edges are shared. This results in an invalid multipolygon for many cases such as applying this function on an ST_Split result.

Availability: 2.0.0

### Examples

      SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0))'));

    	st_astext
    	------------
    	 POINT(0 0)
    	(1 row)

      SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))'));

    	st_astext
    	---------------------
    	 MULTIPOINT(0 0,1 1)
    	(1 row)

### See Also

ST_Multi, ST_CollectionExtract

ST_Force2D

Force the geometries into a "2-dimensional mode".

    			geometry ST_Force2D
    			geometry  geomA

### Description

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates. This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_2D.

&curve_support;

&P_support;

&Z_support;

### Examples

    SELECT ST_AsEWKT(ST_Force2D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    		st_asewkt
    -------------------------------------
    CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)

    SELECT  ST_AsEWKT(ST_Force2D('POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))'));

    				  st_asewkt
    ----------------------------------------------
     POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

### See Also

ST_Force_3D

ST_Force3D

Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.

    			geometry ST_Force3D
    			geometry  geomA

### Description

Forces the geometries into XYZ mode. This is an alias for ST_Force_3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3D.

&P_support;

&curve_support;

&Z_support;

### Examples

    		--Nothing happens to an already 3D geometry
    		SELECT ST_AsEWKT(ST_Force3D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force3D('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

### See Also

ST_AsEWKT, ST_Force2D, ST_Force_3DM, ST_Force_3DZ

ST_Force3DZ

Force the geometries into XYZ mode.

    			geometry ST_Force3DZ
    			geometry  geomA

### Description

Forces the geometries into XYZ mode. This is a synonym for ST_Force3DZ. If a geometry has no Z component, then a 0 Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DZ.

&P_support;

&Z_support;

&curve_support;

### Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force3DZ(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force3DZ('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

### See Also

ST_AsEWKT, ST_Force2D, ST_Force_3DM, ST_Force_3D

ST_Force3DM

Force the geometries into XYM mode.

    			geometry ST_Force3DM
    			geometry  geomA

### Description

Forces the geometries into XYM mode. If a geometry has no M component, then a 0 M coordinate is tacked on. If it has a Z component, then Z is removed

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DM.

&curve_support;

### Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    ------------------------------------------------
     CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)

    SELECT  ST_AsEWKT(ST_Force3DM('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    						  st_asewkt
    ---------------------------------------------------------------
     POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

### See Also

ST_AsEWKT, ST_Force2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

ST_Force4D

Force the geometries into XYZM mode.

    			geometry ST_Force4D
    			geometry  geomA

### Description

Forces the geometries into XYZM mode. 0 is tacked on for missing Z and M dimensions.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_4D.

&Z_support;

&curve_support;

### Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force4D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    						st_asewkt
    ---------------------------------------------------------
     CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)

    SELECT  ST_AsEWKT(ST_Force4D('MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    									  st_asewkt
    --------------------------------------------------------------------------------------
     MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

### See Also

ST_AsEWKT, ST_Force2D, ST_Force_3DM, ST_Force_3D

ST_ForcePolygonCCW

Orients all exterior rings counter-clockwise and all interior rings clockwise.

    						geometry
    						ST_ForcePolygonCCW

    						geometry
    						geom

### Description

Forces (Multi)Polygons to use a counter-clockwise orientation for their exterior ring, and a clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Availability: 2.4.0

&Z_support;

&M_support;

### See Also

ST_ForcePolygonCW, ST_IsPolygonCCW, ST_IsPolygonCW

ST_ForceCollection

Convert the geometry into a GEOMETRYCOLLECTION.

    			geometry ST_ForceCollection
    			geometry  geomA

### Description

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_Collection.

&P_support;

&Z_support;

&curve_support;

### Examples

    SELECT  ST_AsEWKT(ST_ForceCollection('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    								   st_asewkt
    ----------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))

      SELECT ST_AsText(ST_ForceCollection('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));
    								   st_astext
    --------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
    (1 row)

    -- POLYHEDRAL example --
    SELECT ST_AsEWKT(ST_ForceCollection('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_asewkt
    ----------------------------------------------------------------------------------
    GEOMETRYCOLLECTION(
      POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
      POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
      POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
      POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
      POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
      POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
    )

### See Also

ST_AsEWKT, ST_Force2D, ST_Force_3DM, ST_Force_3D, ST_GeomFromEWKT

ST_ForcePolygonCW

Orients all exterior rings clockwise and all interior rings counter-clockwise.

    						geometry
    						ST_ForcePolygonCW

    						geometry
    						geom

### Description

Forces (Multi)Polygons to use a clockwise orientation for their exterior ring, and a counter-clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Availability: 2.4.0

&Z_support;

&M_support;

### See Also

ST_ForcePolygonCCW, ST_IsPolygonCCW, ST_IsPolygonCW

ST_ForceSFS

Force the geometries to use SFS 1.1 geometry types only.

    			geometry ST_ForceSFS
    			geometry  geomA

    			geometry ST_ForceSFS
    			geometry  geomA
    			text  version

### Description

&P_support;

&T_support;

&curve_support;

&Z_support;

ST_ForceRHR

Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

    					geometry
    						ST_ForceRHR
    						geometry g

### Description

Forces the orientation of the vertices in a polygon to follow a Right-Hand-Rule, in which the area that is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise direction and the interior rings in a counter-clockwise direction. This function is a synonym for ST_ForcePolygonCW

The above definition of the Right-Hand-Rule conflicts with definitions used in other contexts. To avoid confusion, it is recommended to use ST_ForcePolygonCW.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

&Z_support;

&P_support;

### Examples

    SELECT ST_AsEWKT(
      ST_ForceRHR(
    	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
      )
    );
    						  st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
    (1 row)

### See Also

ST_ForcePolygonCCW, ST_ForcePolygonCW, ST_IsPolygonCCW, ST_IsPolygonCW, ST_BuildArea, ST_Polygonize, ST_Reverse

ST_ForceCurve

Upcast a geometry into its curved type, if applicable.

    					geometry
    						ST_ForceCurve
    						geometry g

### Description

Turns a geometry into its curved representation, if applicable: lines become compoundcurves, multilines become multicurves polygons become curvepolygons multipolygons become multisurfaces. If the geometry input is already a curved representation returns back same as input.

Availability: 2.2.0

&Z_support;

&curve_support;

### Examples

    SELECT ST_AsText(
      ST_ForceCurve(
    	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'::geometry
      )
    );
                                  st_astext
    ----------------------------------------------------------------------
     CURVEPOLYGON Z ((0 0 2,5 0 2,0 5 2,0 0 2),(1 1 2,1 3 2,3 1 2,1 1 2))
    (1 row)

### See Also

ST_LineToCurve

ST_LineMerge

Return a (set of) LineString(s) formed by sewing together a MULTILINESTRING.

    				geometry ST_LineMerge
    				geometry  amultilinestring

### Description

Returns a (set of) LineString(s) formed by sewing together the constituent line work of a MULTILINESTRING.

Only use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or geometry collection into this function, it will return an empty GEOMETRYCOLLECTION

Performed by the GEOS module.

Availability: 1.1.0

Will strip the M dimension.

### Examples

    SELECT ST_AsText(ST_LineMerge(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
    		)
    );
    st_astext
    --------------------------------------------------------------------------------------------------
    LINESTRING(-29 -27,-30 -29.7,-36 -31,-45 -33,-46 -32)
    (1 row)

    --If can't be merged - original MULTILINESTRING is returned
    SELECT ST_AsText(ST_LineMerge(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45.2 -33.2,-46 -32))')
    )
    );
    st_astext
    ----------------
    MULTILINESTRING((-45.2 -33.2,-46 -32),(-29 -27,-30 -29.7,-36 -31,-45 -33))

    -- example with Z dimension
    SELECT ST_AsText(ST_LineMerge(
    ST_GeomFromText('MULTILINESTRING((-29 -27 11,-30 -29.7 10,-36 -31 5,-45 -33 6), (-29 -27 12,-30 -29.7 5), (-45 -33 1,-46 -32 11))')
    		)
    );
    st_astext
    --------------------------------------------------------------------------------------------------
    LINESTRING Z (-30 -29.7 5,-29 -27 11,-30 -29.7 10,-36 -31 5,-45 -33 1,-46 -32 11)
    (1 row)

### See Also

ST_Segmentize, ST_LineSubstring

ST_Multi

Return the geometry as a MULTI* geometry.

    				geometry ST_Multi
    				geometry  g1

### Description

Returns the geometry as a MULTI* geometry. If the geometry is already a MULTI*, it is returned unchanged.

### Examples

    SELECT ST_AsText(ST_Multi(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    			743265 2967450,743265.625 2967416,743238 2967416))')));
    			st_astext
    			--------------------------------------------------------------------------------------------------
    			MULTIPOLYGON(((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,
    			743238 2967416)))
    			(1 row)

### See Also

ST_AsText

ST_Normalize

Return the geometry in its canonical form.

    				geometry ST_Normalize
    				geometry  geom

### Description

Returns the geometry in its normalized/canonical form. May reorder vertices in polygon rings, rings in a polygon, elements in a multi-geometry complex.

Mostly only useful for testing purposes (comparing expected and obtained results).

Availability: 2.3.0

### Examples

    SELECT ST_AsText(ST_Normalize(ST_GeomFromText(
      'GEOMETRYCOLLECTION(
        POINT(2 3),
        MULTILINESTRING((0 0, 1 1),(2 2, 3 3)),
        POLYGON(
          (0 10,0 0,10 0,10 10,0 10),
          (4 2,2 2,2 4,4 4,4 2),
          (6 8,8 8,8 6,6 6,6 8)
        )
      )'
    )));
                                                                         st_astext
    ----------------------------------------------------------------------------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0,0 10,10 10,10 0,0 0),(6 6,8 6,8 8,6 8,6 6),(2 2,4 2,4 4,2 4,2 2)),MULTILINESTRING((2 2,3 3),(0 0,1 1)),POINT(2 3))
    (1 row)

### See Also

ST_Equals,

ST_QuantizeCoordinates

Sets least significant bits of coordinates to zero

    						geometry
    						ST_QuantizeCoordinates

    						geometry
    						g

    						int
    						prec_x

    						int
    						prec_y

    						int
    						prec_z

    						int
    						prec_m

### Description

`ST_QuantizeCoordinates` determines the number of bits (`N`) required to represent a coordinate value with a specified number of digits after the decimal point, and then sets all but the `N` most significant bits to zero. The resulting coordinate value will still round to the original value, but will have improved compressiblity. This can result in a significant disk usage reduction provided that the geometry column is using a compressible storage type. The function allows specification of a different number of digits after the decimal point in each dimension; unspecified dimensions are assumed to have the precsion of the `x` dimension. Negative digits are interpreted to refer digits to the left of the decimal point, (i.e., `prec_x=-2` will preserve coordinate values to the nearest 100.

The coordinates produced by `ST_QuantizeCoordinates` are independent of the geometry that contains those coordinates and the relative position of those coordinates within the geometry. As a result, existing topological relationships between geometries are unaffected by use of this function. The function may produce invalid geometry when it is called with a number of digits lower than the intrinsic precision of the geometry.

Availability: 2.5.0

### Technical Background

PostGIS stores all coordinate values as double-precision floating point integers, which can reliably represent 15 significant digits. However, PostGIS may be used to manage data that intrinsically has fewer than 15 significant digits. An example is TIGER data, which is provided as geographic coordinates with six digits of precision after the decimal point (thus requiring only nine significant digits of longitude and eight significant digits of latitude.)

When 15 significant digits are available, there are many possible representations of a number with 9 significant digits. A double precision floating point number uses 52 explicit bits to represent the significand (mantissa) of the coordinate. Only 30 bits are needed to represent a mantissa with 9 significant digits, leaving 22 insignificant bits; we can set their value to anything we like and still end up with a number that rounds to our input value. For example, the value 100.123456 can be represented by the floating point numbers closest to 100.123456000000, 100.123456000001, and 100.123456432199. All are equally valid, in that `ST_AsText(geom, 6)` will return the same result with any of these inputs. As we can set these bits to any value, `ST_QuantizeCoordinates` sets the 22 insignificant bits to zero. For a long coordinate sequence this creates a pattern of blocks of consecutive zeros that is compressed by PostgreSQL more effeciently.

Only the on-disk size of the geometry is potentially affected by `ST_QuantizeCoordinates`. ST_MemSize, which reports the in-memory usage of the geometry, will return the the same value regardless of the disk space used by a geometry.

### Examples

    SELECT ST_AsText(ST_QuantizeCoordinates('POINT (100.123456 0)'::geometry, 4));
    st_astext
    -------------------------
    POINT(100.123455047607 0)

    WITH test AS (SELECT 'POINT (123.456789123456 123.456789123456)'::geometry AS geom)
    SELECT
      digits,
      encode(ST_QuantizeCoordinates(geom, digits), 'hex'),
      ST_AsText(ST_QuantizeCoordinates(geom, digits))
    FROM test, generate_series(15, -15, -1) AS digits;

    digits  |                   encode                   |                st_astext
    --------+--------------------------------------------+------------------------------------------
    15      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    14      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    13      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    12      | 01010000005c9a72083cdd5e405c9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    11      | 0101000000409a72083cdd5e40409a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    10      | 0101000000009a72083cdd5e40009a72083cdd5e40 | POINT(123.456789123455 123.456789123455)
    9       | 0101000000009072083cdd5e40009072083cdd5e40 | POINT(123.456789123418 123.456789123418)
    8       | 0101000000008072083cdd5e40008072083cdd5e40 | POINT(123.45678912336 123.45678912336)
    7       | 0101000000000070083cdd5e40000070083cdd5e40 | POINT(123.456789121032 123.456789121032)
    6       | 0101000000000040083cdd5e40000040083cdd5e40 | POINT(123.456789076328 123.456789076328)
    5       | 0101000000000000083cdd5e40000000083cdd5e40 | POINT(123.456789016724 123.456789016724)
    4       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
    3       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
    2       | 01010000000000000038dd5e400000000038dd5e40 | POINT(123.45654296875 123.45654296875)
    1       | 01010000000000000000dd5e400000000000dd5e40 | POINT(123.453125 123.453125)
    0       | 01010000000000000000dc5e400000000000dc5e40 | POINT(123.4375 123.4375)
    -1      | 01010000000000000000c05e400000000000c05e40 | POINT(123 123)
    -2      | 01010000000000000000005e400000000000005e40 | POINT(120 120)
    -3      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -4      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -5      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -6      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -7      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -8      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -9      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -10     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -11     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -12     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -13     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -14     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -15     | 010100000000000000000058400000000000005840 | POINT(96 96)

### See Also

ST_SnapToGrid

ST_RemovePoint

Remove point from a linestring.

    			geometry ST_RemovePoint
    			geometry linestring
    			integer offset

### Description

Remove a point from a linestring, given its 0-based index. Useful for turning a closed ring into an open line string

Availability: 1.1.0

&Z_support;

### Examples

    --guarantee no LINESTRINGS are closed
    --by removing the end point.  The below assumes the_geom is of type LINESTRING
    UPDATE sometable
    	SET the_geom = ST_RemovePoint(the_geom, ST_NPoints(the_geom) - 1)
    	FROM sometable
    	WHERE ST_IsClosed(the_geom) = true;

### See Also

ST_AddPoint, ST_NPoints, ST_NumPoints

ST_Reverse

Return the geometry with vertex order reversed.

    			geometry ST_Reverse
    			geometry  g1

### Description

Can be used on any geometry and reverses the order of the vertexes.

Enhanced: 2.4.0 support for curves was introduced.

&Z_support;

&P_support;

### Examples

    SELECT ST_AsText(the_geom) as line, ST_AsText(ST_Reverse(the_geom)) As reverseline
    FROM
    (SELECT ST_MakeLine(ST_MakePoint(1,2),
    		ST_MakePoint(1,10)) As the_geom) as foo;
    --result
    		line         |     reverseline
    ---------------------+----------------------
    LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)

ST_Segmentize

Return a modified geometry/geography having no segment longer than the given distance.

    				geometry ST_Segmentize
    				geometry  geom
    				float  max_segment_length

    				geography ST_Segmentize
    				geography  geog
    				float  max_segment_length

### Description

Returns a modified geometry having no segment longer than the given `max_segment_length`. Distance computation is performed in 2d only. For geometry, length units are in units of spatial reference. For geography, units are in meters.

Availability: 1.2.2

Enhanced: 3.0.0 Segmentize geometry now uses equal length segments

Enhanced: 2.3.0 Segmentize geography now uses equal length segments

Enhanced: 2.1.0 support for geography was introduced.

Changed: 2.1.0 As a result of the introduction of geography support: The construct `SELECT ST_Segmentize('LINESTRING(1 2, 3 4)',0.5);` will result in ambiguous function error. You need to have properly typed object e.g. a geometry/geography column, use ST_GeomFromText, ST_GeogFromText or `SELECT ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry,0.5);`

This will only increase segments. It will not lengthen segments shorter than max length

### Examples

    SELECT ST_AsText(ST_Segmentize(
    ST_GeomFromText('MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45 -33,-46 -32))')
    		,5)
    );
    st_astext
    --------------------------------------------------------------------------------------------------
    MULTILINESTRING((-29 -27,-30 -29.7,-34.886615700134 -30.758766735029,-36 -31,
    -40.8809353009198 -32.0846522890933,-45 -33),
    (-45 -33,-46 -32))
    (1 row)

    SELECT ST_AsText(ST_Segmentize(ST_GeomFromText('POLYGON((-29 28, -30 40, -29 28))'),10));
    st_astext
    -----------------------
    POLYGON((-29 28,-29.8304547985374 37.9654575824488,-30 40,-29.1695452014626 30.0345424175512,-29 28))
    (1 row)

### See Also

ST_LineSubstring

ST_SetPoint

Replace point of a linestring with a given point.

    				geometry ST_SetPoint
    				geometry linestring
    				integer zerobasedposition
    				geometry point

### Description

Replace point N of linestring with given point. Index is 0-based.Negative index are counted backwards, so that -1 is last point. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.

Availability: 1.1.0

Updated 2.3.0 : negative indexing

&Z_support;

### Examples

    --Change first point in line string from -1 3 to -1 1
    SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
    	   st_astext
    -----------------------
     LINESTRING(-1 1,-1 3)

    ---Change last point in a line string (lets play with 3d linestring this time)
    SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
    FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As the_geom) As foo;
    	   st_asewkt
    -----------------------
    LINESTRING(-1 2 3,-1 3 4,-1 1 3)

    SELECT ST_AsText(ST_SetPoint(g, -3, p))
    FROM ST_GEomFromText('LINESTRING(0 0, 1 1, 2 2, 3 3, 4 4)') AS g
    	, ST_PointN(g,1) as p;
    	   st_astext
    -----------------------
    LINESTRING(0 0,1 1,0 0,3 3,4 4)

### See Also

ST_AddPoint, ST_NPoints, ST_NumPoints, ST_PointN, ST_RemovePoint

ST_SnapToGrid

Snap all points of the input geometry to a regular grid.

    			geometry ST_SnapToGrid
    			geometry  geomA
    			float  originX
    			float  originY
    			float  sizeX
    			float  sizeY

    			geometry ST_SnapToGrid
    			geometry  geomA
    			float  sizeX
    			float  sizeY

    			geometry ST_SnapToGrid
    			geometry  geomA
    			float  size

    			geometry ST_SnapToGrid
    			geometry  geomA
    			geometry  pointOrigin
    			float  sizeX
    			float  sizeY
    			float  sizeZ
    			float  sizeM

### Description

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don't want to snap to a grid.

The returned geometry might lose its simplicity (see ST_IsSimple).

Before release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have same dimensionality as the input one with higher dimension values untouched. Use the version taking a second geometry argument to define all grid dimensions.

Availability: 1.0.0RC1

Availability: 1.1.0 - Z and M support

&Z_support;

### Examples

    --Snap your geometries to a precision grid of 10^-3
    UPDATE mytable
       SET the_geom = ST_SnapToGrid(the_geom, 0.001);

    SELECT ST_AsText(ST_SnapToGrid(
    			ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
    			0.001)
    		);
    			  st_astext
    -------------------------------------
     LINESTRING(1.112 2.123,4.111 3.237)
     --Snap a 4d geometry
    SELECT ST_AsEWKT(ST_SnapToGrid(
    	ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
    		4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
     ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
     0.1, 0.1, 0.1, 0.01) );
    								  st_asewkt
    ------------------------------------------------------------------------------
     LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)

    --With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
    SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
    		4.111111 3.2374897 3.1234 1.1111)'),
    	   0.01)      );
    						st_asewkt
    ---------------------------------------------------------
     LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

### See Also

ST_Snap, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_GeomFromEWKT, ST_Simplify

ST_Snap

Snap segments and vertices of input geometry to vertices of a reference geometry.

    			geometry ST_Snap
    			geometry  input
    			geometry  reference
    			float  tolerance

### Description

Snaps the vertices and segments of a geometry to another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed. The result geometry is the input geometry with the vertices snapped. If no snapping occurs then the input geometry is returned unchanged.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

The returned geometry might lose its simplicity (see ST_IsSimple) and validity (see ST_IsValid).

Performed by the GEOS module.

Availability: 2.0.0

### Examples

A multipolygon shown with a linestring (before any snapping)
A multipolygon snapped to linestring to tolerance: 1.01 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly,line)*1.01)) AS polysnapped
    FROM (SELECT
       ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
     MULTIPOLYGON(((26 125,26 200,126 200,126 125,101 100,26 125),
     (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
| A multipolygon snapped to linestring to tolerance: 1.25 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(
        ST_Snap(poly,line, ST_Distance(poly,line)*1.25)
      ) AS polysnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
        (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
    MULTIPOLYGON(((5 107,26 200,126 200,126 125,101 100,54 84,5 107),
    (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
The linestring snapped to the original multipolygon at tolerance 1.01 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
       ST_Snap(line, poly, ST_Distance(poly,line)*1.01)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100)))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                  linesnapped
    ----------------------------------------
     LINESTRING(5 107,26 125,54 84,101 100)
| The linestring snapped to the original multipolygon at tolerance 1.25 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
     ST_Snap(line, poly, ST_Distance(poly,line)*1.25)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;
                  linesnapped
    ---------------------------------------
    LINESTRING(26 125,54 84,101 100)

### See Also

ST_SnapToGrid

ST_SwapOrdinates

Returns a version of the given geometry with given ordinate values swapped.

    			geometry ST_SwapOrdinates
    			geometry geom
    			cstring ords

### Description

Returns a version of the given geometry with given ordinates swapped.

The `ords` parameter is a 2-characters string naming the ordinates to swap. Valid names are: x,y,z and m.

Availability: 2.2.0

&curve_support;

&Z_support;

&M_support;

&P_support;

&T_support;

### Example

    -- Scale M value by 2
    SELECT ST_AsText(
      ST_SwapOrdinates(
        ST_Scale(
          ST_SwapOrdinates(g,'xm'),
          2, 1
        ),
      'xm')
    ) FROM ( SELECT 'POINT ZM (0 0 0 2)'::geometry g ) foo;
         st_astext
    --------------------
     POINT ZM (0 0 0 4)

### See Also

ST_FlipCoordinates