# Geometry Constructors

ST_Collect

Creates a GeometryCollection or Multi* geometry from a set of geometries.

    				geometry ST_Collect
    					geometry g1
    					geometry g2

    				geometry ST_Collect
    					geometry[] g1_array

    				geometry ST_Collect
    					geometry set g1field

### Description

Collects geometries into a geometry collection. The result is either a Multi* or a GeometryCollection, depending on whether the input geometries have the same or different types (homogeneous or heterogeneous). The input geometries are left unchanged within the collection.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries.

If any of the input geometries are collections (Multi* or GeometryCollection) ST_Collect returns a GeometryCollection (since that is the only type which can contain nested collections). To prevent this, use ST_Dump in a subquery to expand the input collections to their atomic elements (see example below).

ST_Collect and ST_Union appear similar, but in fact operate quite differently. ST_Collect aggregates geometries into a collection without changing them in any way. ST_Union geometrically merges geometries where they overlap, and splits linestrings at intersections. It may return single geometries when it dissolves boundaries.

Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.

&Z_support;

&curve_support;

### Examples - Two-input variant

Collect 2D points.

    SELECT ST_AsText( ST_Collect( ST_GeomFromText('POINT(1 2)'),
    	ST_GeomFromText('POINT(-2 3)') ));

    st_astext
    ----------
    MULTIPOINT(1 2,-2 3)

Collect 3D points.

    SELECT ST_AsEWKT( ST_Collect( ST_GeomFromEWKT('POINT(1 2 3)'),
    		ST_GeomFromEWKT('POINT(1 2 4)') ) );

    		st_asewkt
    -------------------------
     MULTIPOINT(1 2 3,1 2 4)

Collect curves.

    SELECT ST_AsText( ST_Collect( 'CIRCULARSTRING(220268 150415,220227 150505,220227 150406)',
    		'CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));

    		st_astext
    ------------------------------------------------------------------------------------
    MULTICURVE(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),
     CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

### Examples - Array variant

Using an array constructor for a subquery.

    SELECT ST_Collect( ARRAY( SELECT geom FROM sometable ) );

Using an array constructor for values.

    SELECT ST_AsText(  ST_Collect(
    		ARRAY[ ST_GeomFromText('LINESTRING(1 2, 3 4)'),
    			ST_GeomFromText('LINESTRING(3 4, 4 5)') ] )) As wktcollect;

    --wkt collect --
    MULTILINESTRING((1 2,3 4),(3 4,4 5))

### Examples - Aggregate variant

Creating multiple collections by grouping geometries in a table.

    SELECT stusps, ST_Collect(f.geom) as geom
    	 FROM (SELECT stusps, (ST_Dump(geom)).geom As geom
    				FROM
    				somestatetable ) As f
    	GROUP BY stusps

### See Also

ST_Dump, ST_Union

ST_LineFromMultiPoint

Creates a LineString from a MultiPoint geometry.

    			geometry ST_LineFromMultiPoint
    			geometry  aMultiPoint

### Description

Creates a LineString from a MultiPoint geometry.

Use ST_MakeLine to create lines from Point or LineString inputs.

&Z_support;

### Examples

Create a 3D line string from a 3D MultiPoint

    SELECT ST_AsEWKT(  ST_LineFromMultiPoint('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')  ));

    --result--
    LINESTRING(1 2 3,4 5 6,7 8 9)

### See Also

ST_AsEWKT, ST_MakeLine

ST_MakeEnvelope

Creates a rectangular Polygon from minimum and maximum coordinates.

    			geometry ST_MakeEnvelope
    			float xmin
    			float ymin
    			float xmax
    			float ymax
    			integer srid=unknown

### Description

Creates a rectangular Polygon from the minimum and maximum values for X and Y. Input values must be in the spatial reference system specified by the SRID. If no SRID is specified the unknown spatial reference system (SRID 0) is used.

Availability: 1.5

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

### Example: Building a bounding box polygon

    SELECT ST_AsText( ST_MakeEnvelope(10, 10, 11, 11, 4326) );

    st_asewkt
    -----------
    POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))

### See Also

ST_MakePoint, ST_MakeLine, ST_MakePolygon, ST_TileEnvelope

ST_MakeLine

Creates a LineString from Point, MultiPoint, or LineString geometries.

    				geometry ST_MakeLine
    				geometry geom1
    				geometry geom2

    				geometry ST_MakeLine
    				geometry[] geoms_array

    				geometry ST_MakeLine
    				geometry set geoms

### Description

Creates a LineString containing the points of Point, MultiPoint, or LineString geometries. Other geometry types cause an error.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries. To ensure the order of the input geometries use `ORDER BY` in the function call, or a subquery with an `ORDER BY` clause.

Repeated nodes at the beginning of input LineStrings are collapsed to a single point. Repeated points in Point and MultiPoint inputs are not collapsed. ST_RemoveRepeatedPoints can be used to collapse repeated points from the output LineString.

&Z_support;

Availability: 2.3.0 - Support for MultiPoint input elements was introduced

Availability: 2.0.0 - Support for LineString input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

### Examples: Two-input variant

Create a line composed of two points.

    SELECT ST_AsText( ST_MakeLine(ST_Point(1,2), ST_Point(3,4)) );

    	  st_astext
    ---------------------
     LINESTRING(1 2,3 4)

Create a 3D line from two 3D points.

    SELECT ST_AsEWKT( ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5) ));

    		st_asewkt
    -------------------------
     LINESTRING(1 2 3,3 4 5)

Create a line from two disjoint LineStrings.

     select ST_AsText( ST_MakeLine( 'LINESTRING(0 0, 1 1)', 'LINESTRING(2 2, 3 3)' ) );

              st_astext
    -----------------------------
     LINESTRING(0 0,1 1,2 2,3 3)

### Examples: Array variant

Create a line from an array formed by a subquery with ordering.

    SELECT ST_MakeLine( ARRAY( SELECT ST_Centroid(geom) FROM visit_locations ORDER BY visit_time) );

Create a 3D line from an array of 3D points

    SELECT ST_AsEWKT( ST_MakeLine(
              ARRAY[ ST_MakePoint(1,2,3), ST_MakePoint(3,4,5), ST_MakePoint(6,6,6) ]  ));

    		st_asewkt
    -------------------------
    LINESTRING(1 2 3,3 4 5,6 6 6)

### Examples: Aggregate variant

This example queries time-based sequences of GPS points from a set of tracks and creates one record for each track. The result geometries are LineStrings composed of the GPS track points in the order of travel.

Using aggregate `ORDER BY` provides a correctly-ordered LineString.

    SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) As geom
    	FROM gps_points As gps
    	GROUP BY track_id;

Prior to PostgreSQL 9, ordering in a subquery can be used. However, sometimes the query plan may not respect the order of the subquery.

    SELECT gps.track_id, ST_MakeLine(gps.geom) As geom
    	FROM ( SELECT track_id, gps_time, geom
    			FROM gps_points ORDER BY track_id, gps_time ) As gps
    	GROUP BY track_id;

### See Also

ST_RemoveRepeatedPoints, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_MakePoint, ST_Point

ST_MakePoint

Creates a 2D, 3DZ or 4D Point.

    			geometry ST_MakePoint
    			float x
    			float y

    			geometry ST_MakePoint
    			float x
    			float y
    			float z

    			geometry ST_MakePoint
    			float x
    			float y
    			float z
    			float m

### Description

Creates a 2D, 3D Z or 4D ZM Point geometry.

Use ST_MakePointM to make points with XYM coordinates.

While not OGC-compliant, `ST_MakePoint` is faster and more precise than ST_GeomFromText and ST_PointFromText. It is also easier to use for numeric coordinate values.

For geodetic coordinates, `X` is longitude and `Y` is latitude

&Z_support;

### Examples

    --Return point with unknown SRID
    SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

    --Return point marked as WGS 84 long lat
    SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

    --Return a 3D point (e.g. has altitude)
    SELECT ST_MakePoint(1, 2,1.5);

    --Get z of point
    SELECT ST_Z(ST_MakePoint(1, 2,1.5));
    result
    -------
    1.5

### See Also

ST_GeomFromText, ST_PointFromText, ST_SetSRID, ST_MakePointM

ST_MakePointM

Creates a Point from X, Y and M values.

    				geometry ST_MakePointM
    				float x
    				float y
    				float m

### Description

Creates a point with X, Y and M (measure) coordinates.

Use ST_MakePoint to make points with XY, XYZ, or XYZM coordinates.

For geodetic coordinates, `X` is longitude and `Y` is latitude

### Examples

ST_AsEWKT is used for text output because ST_AsText does not support M values.

Create point with unknown SRID.

    SELECT ST_AsEWKT(  ST_MakePointM(-71.1043443253471, 42.3150676015829, 10)  );

    				   st_asewkt
    -----------------------------------------------
     POINTM(-71.1043443253471 42.3150676015829 10)

Create point with a measure in the WGS 84 geodetic coordinate system.

    SELECT ST_AsEWKT( ST_SetSRID(  ST_MakePointM(-71.104, 42.315, 10),  4326));

    						st_asewkt
    ---------------------------------------------------------
    SRID=4326;POINTM(-71.104 42.315 10)

Get measure of created point.

    SELECT ST_M(  ST_MakePointM(-71.104, 42.315, 10)  );

    result
    -------
    10

### See Also

ST_AsEWKT, ST_MakePoint, ST_SetSRID

ST_MakePolygon

Creates a Polygon from a shell and optional list of holes.

    			geometry ST_MakePolygon
    			geometry linestring

    			geometry ST_MakePolygon
    			geometry outerlinestring
    			geometry[] interiorlinestrings

### Description

Creates a Polygon formed by the given shell and optional array of holes. Input geometries must be closed LineStrings (rings).

Variant 1: Accepts one shell LineString.

Variant 2: Accepts a shell LineString and an array of inner (hole) LineStrings. A geometry array can be constructed using the PostgreSQL array_agg(), ARRAY[] or ARRAY() constructs.

This function does not accept MultiLineStrings. Use ST_LineMerge to generate a LineString, or ST_Dump to extract LineStrings.

&Z_support;

### Examples: Single input variant

Create a Polygon from a 2D LineString.

    SELECT ST_MakePolygon( ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)'));

Create a Polygon from an open LineString, using ST_StartPoint and ST_AddPoint to close it.

    SELECT ST_MakePolygon( ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)) )
    FROM (
      SELECT ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)') As open_line) As foo;

Create a Polygon from a 3D LineString

    SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

    st_asewkt
    -----------
    POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

Create a Polygon from a LineString with measures

    SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)' ));

    st_asewkt
    ----------
    POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))

### Examples: Outer shell with inner holes variant

Create a donut Polygon with an extra hole

    SELECT ST_MakePolygon( ST_ExteriorRing( ST_Buffer(ring.line,10)),
    	ARRAY[  ST_Translate(ring.line, 1, 1),
    		ST_ExteriorRing(ST_Buffer(ST_Point(20,20),1)) ]
    	)
    FROM (SELECT ST_ExteriorRing(
    	ST_Buffer(ST_Point(10,10),10,10)) AS line ) AS ring;

Create a set of province boundaries with holes representing lakes. The input is a table of province Polygons/MultiPolygons and a table of water linestrings. Lines forming lakes are determined by using ST_IsClosed. The province linework is extracted by using ST_Boundary. As required by `ST_MakePolygon`, the boundary is forced to be a single LineString by using ST_LineMerge. (However, note that if a province has more than one region or has islands this will produce an invalid polygon.) Using a LEFT JOIN ensures all provinces are included even if they have no lakes.

The CASE construct is used because passing a null array into ST_MakePolygon results in a NULL return value.

    SELECT p.gid, p.province_name,
    	CASE WHEN array_agg(w.geom) IS NULL
    	THEN p.geom
    	ELSE  ST_MakePolygon( ST_LineMerge(ST_Boundary(p.geom)),
                            array_agg(w.geom)) END
    FROM
    	provinces p LEFT JOIN waterlines w
    		ON (ST_Within(w.geom, p.geom) AND ST_IsClosed(w.geom))
    GROUP BY p.gid, p.province_name, p.geom;

Another technique is to utilize a correlated subquery and the ARRAY() constructor that converts a row set to an array.

    SELECT p.gid,  p.province_name,
        CASE WHEN EXISTS( SELECT w.geom
            FROM waterlines w
            WHERE ST_Within(w.geom, p.geom)
            AND ST_IsClosed(w.geom))
        THEN ST_MakePolygon(
            ST_LineMerge(ST_Boundary(p.geom)),
            ARRAY( SELECT w.geom
                FROM waterlines w
                WHERE ST_Within(w.geom, p.geom)
                AND ST_IsClosed(w.geom)))
        ELSE p.geom
        END AS geom
    FROM provinces p;

### See Also

ST_BuildArea ST_Polygon

ST_Point

Creates a Point with the given coordinate values. Alias for ST_MakePoint.

    			geometry ST_Point
    			float x
    			float y

                geometry ST_Point
                float x
                float y
                integer srid=unknown

### Description

Returns an Point with the given X and Y coordinate values. This is the SQL-MM alias for ST_MakePoint that takes just X and Y.

For geodetic coordinates, `X` is longitude and `Y` is latitude

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry. Creates a Point with X, Y and SRID values.

&sqlmm_compliant; SQL-MM 3: 6.1.2

### Examples: Geometry

    SELECT ST_SetSRID( ST_Point( -71.104, 42.315), 4326)

### Examples: Geography

Pre-PostGIS 3.2 syntax

    SELECT CAST( ST_SetSRID(ST_Point( -71.104, 42.315), 4326) AS geography);

3.2 and on you can include the srid

    SELECT CAST( ST_Point( -71.104, 42.315, 4326) AS geography);

PostgreSQL also provides the `::` short-hand for casting

    SELECT ST_Point( -71.104, 42.315, 4326)::geography;

If the point coordinates are not in a geodetic coordinate system (such as WGS84), then they must be reprojected before casting to a geography. In this example a point in Pennsylvania State Plane feet (SRID 2273) is projected to WGS84 (SRID 4326).

    SELECT ST_Transform(ST_SetSRID( ST_Point( 3637510, 3014852 ), 2273), 4326)::geography;

### See Also

PostGIS_Geography, ST_MakePoint, ST_SetSRID, ST_Transform, ST_PointZ, ST_PointM, ST_PointZM

ST_PointZ

Creates a Point with the given coordinate and SRID values.

                geometry ST_PointZ
                float x
                float y
                float z
                integer srid=unknown

### Description

Returns an Point with the given X, Y and Z coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

### Examples

    SELECT ST_PointZ(-71.104, 42.315, 3.4, 4326)

    SELECT ST_PointZ(-71.104, 42.315, 3.4, srid => 4326)

    SELECT ST_PointZ(-71.104, 42.315, 3.4)

### See Also

ST_MakePoint, ST_Point, ST_PointM, ST_PointZM

ST_PointM

Creates a Point with the given coordinate and SRID values.

                geometry ST_PointZ
                float x
                float y
                float m
                integer srid=unknown

### Description

Returns an Point with the given X, Y and M coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

### Examples

    SELECT ST_PointM(-71.104, 42.315, 3.4, 4326)

    SELECT ST_PointM(-71.104, 42.315, 3.4, srid => 4326)

    SELECT ST_PointM(-71.104, 42.315, 3.4)

### See Also

ST_MakePoint, ST_Point, ST_PointZ, ST_PointZM

ST_PointZM

Creates a Point with the given coordinate and SRID values.

                geometry ST_PointZM
                float x
                float y
                float z
                float m
                integer srid=unknown

### Description

Returns an Point with the given X, Y, Z and M coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

### Examples

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, 4326)

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, srid => 4326)

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5)

### See Also

ST_MakePoint, ST_Point, ST_PointM, ST_PointZ, ST_SetSRID

ST_Polygon

Creates a Polygon from a LineString with a specified SRID.

    			geometry ST_Polygon
    			geometry  lineString
    			integer  srid

### Description

Returns a polygon built from the given LineString and sets the spatial reference system from the `srid`.

ST_Polygon is similar to ST_MakePolygon Variant 1 with the addition of setting the SRID.

To create polygons with holes use ST_MakePolygon Variant 2 and then ST_SetSRID.

This function does not accept MultiLineStrings. Use ST_LineMerge to generate a LineString, or ST_Dump to extract LineStrings.

&sfs_compliant;

&sqlmm_compliant; SQL-MM 3: 8.3.2

&Z_support;

### Examples

Create a 2D polygon.

    SELECT ST_AsText( ST_Polygon('LINESTRING(75 29, 77 29, 77 29, 75 29)'::geometry, 4326) );

    -- result --
    POLYGON((75 29, 77 29, 77 29, 75 29))

Create a 3D polygon.

    SELECT ST_AsEWKT( ST_Polygon( ST_GeomFromEWKT('LINESTRING(75 29 1, 77 29 2, 77 29 3, 75 29 1)'), 4326) );

    -- result --
    SRID=4326;POLYGON((75 29 1, 77 29 2, 77 29 3, 75 29 1))

### See Also

ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_GeomFromText, ST_LineMerge, ST_MakePolygon

ST_TileEnvelope

Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.

    			geometry ST_TileEnvelope
    			integer tileZoom
    			integer tileX
    			integer tileY
    			geometry bounds=SRID=3857;LINESTRING(-20037508.342789 -20037508.342789,20037508.342789 20037508.342789)
    			float margin=0.0

### Description

Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system. By default, the bounds are the in EPSG:3857 using the standard range of the Web Mercator system (-20037508.342789, 20037508.342789). The optional bounds parameter can be used to generate envelopes for any tiling scheme: provide a geometry that has the SRID and extent of the initial "zoom level zero" square within which the tile system is to be inscribed.

The optional margin parameter can be used to grow a tile by the given percentage, e.g. margin=0.125 grows the tile by 12.5%, which is equivalent to buffer=512 when extent is 4096, as used in ST_AsMVTGeom. This is useful to create a tile buffer -- to include data lying outside of the tile's visible area, but whose existence affects current tile's rendering. For example, a city name (a geopoint) could be near an edge of a tile, but the text would need to render on two tiles, even though the geopoint is located in the visible area of just one tile. Using an expanded tile in a search would include the city geopoint for both tiles. Use negative value to shrink the tile instead. Values less than -0.5 are prohibited because that would eliminate the tile completely. Do not use margin with ST_AsMVTGeom(). See example in ST_AsMVT.

Enhanced: 3.1.0 Added margin parameter.

Availability: 3.0.0

### Example: Building a tile envelope

    SELECT ST_AsText( ST_TileEnvelope(2, 1, 1) );

     st_astext
    ------------------------------
     POLYGON((-10018754.1713945 0,-10018754.1713945 10018754.1713945,0 10018754.1713945,0 0,-10018754.1713945 0))

    SELECT ST_AsText( ST_TileEnvelope(3, 1, 1, ST_MakeEnvelope(-180, -90, 180, 90, 4326) ) );

                          st_astext
    ------------------------------------------------------
     POLYGON((-135 45,-135 67.5,-90 67.5,-90 45,-135 45))

### See Also

ST_MakeEnvelope

ST_HexagonGrid

Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.

    			setof record ST_HexagonGrid
    			float8 size
    			geometry bounds

### Description

Starts with the concept of a hexagon tiling of the plane. (Not a hexagon tiling of the globe, this is not the H3 tiling scheme.) For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique hexagonal tiling of the plane, Tiling(SRS, Size). This function answers the question: what hexagons in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output hexagons is the SRS provided by the bounds geometry.

Doubling or tripling the edge size of the hexagon generates a new parent tiling that fits with the origin tiling. Unfortunately, it is not possible to generate parent hexagon tilings that the child tiles perfectly fit inside.

Availability: 3.1.0

### Example: Counting points in hexagons

To do a point summary against a hexagonal tiling, generate a hexagon grid using the extent of the points as the bounds, then spatially join to that grid.

    SELECT COUNT(*), hexes.geom
    FROM
        ST_HexagonGrid(
            10000,
            ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
        ) AS hexes
        INNER JOIN
        pointtable AS pts
        ON ST_Intersects(pts.geom, hexes.geom)
    GROUP BY hexes.geom;

### Example: Generating hex coverage of polygons

If we generate a set of hexagons for each polygon boundary and filter out those that do not intersect their hexagons, we end up with a tiling for each polygon.

Tiling states results in a hexagon coverage of each state, and multiple hexagons overlapping at the borders between states.

The LATERAL keyword is implied for set-returning functions when referring to a prior table in the FROM list. So CROSS JOIN LATERAL, CROSS JOIN, or just plain , are equivalent constructs for this example.

    SELECT admin1.gid, hex.geom
    FROM
        admin1
        CROSS JOIN
        ST_HexagonGrid(100000, admin1.geom) AS hex
    WHERE
        adm0_a3 = 'USA'
        AND
        ST_Intersects(admin1.geom, hex.geom)

### See Also

ST_EstimatedExtent, ST_SetSRID, ST_SquareGrid, ST_TileEnvelope

ST_Hexagon

Returns a single hexagon, using the provided edge size and cell coordinate within the hexagon grid space.

    			geometry ST_Hexagon
    			float8 size
    			integer cell_i
    			integer cell_j
    			geometry origin

### Description

Uses the same hexagon tiling concept as ST_HexagonGrid, but generates just one hexagon at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Hexagons are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Availability: 3.1.0

### Example: Creating a hexagon at the origin

    SELECT ST_AsText(ST_SetSRID(ST_Hexagon(1.0, 0, 0), 3857));

    POLYGON((-1 0,-0.5
             -0.866025403784439,0.5
             -0.866025403784439,1
             0,0.5
             0.866025403784439,-0.5
             0.866025403784439,-1 0))

### See Also

ST_TileEnvelope, ST_HexagonGrid, ST_Square

ST_SquareGrid

Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.

                setof record ST_SquareGrid
                float8 size
                geometry bounds

### Description

Starts with the concept of a square tiling of the plane. For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique square tiling of the plane, Tiling(SRS, Size). This function answers the question: what grids in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output squares is the SRS provided by the bounds geometry.

Doubling or edge size of the square generates a new parent tiling that perfectly fits with the original tiling. Standard web map tilings in mercator are just powers-of-two square grids in the mercator plane.

Availability: 3.1.0

### Example: Generating a 1 degree grid for a country

The grid will fill the whole bounds of the country, so if you want just squares that touch the country you will have to filter afterwards with ST_Intersects.

    WITH grid AS (
    SELECT (ST_SquareGrid(1, ST_Transform(geom,4326))).*
    FROM admin0 WHERE name = 'Canada'
    )
      SELEcT ST_AsText(geom)
      FROM grid

### Example: Counting points in squares (using single chopped grid)

To do a point summary against a square tiling, generate a square grid using the extent of the points as the bounds, then spatially join to that grid. Note the estimated extent might be off from actual extent, so be cautious and at very least make sure you've analyzed your table.

    SELECT COUNT(*), squares.geom
        FROM
        pointtable AS pts
        INNER JOIN
        ST_SquareGrid(
            1000,
            ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
        ) AS squares
        ON ST_Intersects(pts.geom, squares.geom)
        GROUP BY squares.geom

### Example: Counting points in squares using set of grid per point

This yields the same result as the first example but will be slower for a large number of points

    SELECT COUNT(*), squares.geom
        FROM
        pointtable AS pts
        INNER JOIN
        ST_SquareGrid(
            1000,
           pts.geom
        ) AS squares
        ON ST_Intersects(pts.geom, squares.geom)
        GROUP BY squares.geom

### See Also

ST_TileEnvelope, ST_HexagonGrid , ST_EstimatedExtent , ST_SetSRID

ST_Square

Returns a single square, using the provided edge size and cell coordinate within the square grid space.

    			geometry ST_Square
    			float8 size
    			integer cell_i
    			integer cell_j
    			geometry origin

### Description

Uses the same square tiling concept as ST_SquareGrid, but generates just one square at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Squares are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Availability: 3.1.0

### Example: Creating a square at the origin

    SELECT ST_AsText(ST_SetSRID(ST_Square(1.0, 0, 0), 3857));

     POLYGON((0 0,0 1,1 1,1 0,0 0))

### See Also

ST_TileEnvelope, ST_SquareGrid, ST_Hexagon