Spatial Relationships and Measurements
ST_3DClosestPoint
Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of
the 3D shortest line.
geometry ST_3DClosestPoint
geometry
g1
geometry
g2
Description
Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of
the 3D shortest line. The 3D length of the 3D shortest line is the 3D distance.
&Z_support;
&P_support;
Availability: 2.0.0
Examples
linestring and point -- both 3d and 2d closest point
SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
) As foo;
cp3d_line_pt | cp2d_line_pt
-----------------------------------------------------------+------------------------------------------
POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(73.0769230769231 115.384615384615)
linestring and multipoint -- both 3d and 2d closest point
SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
) As foo;
cp3d_line_pt | cp2d_line_pt
-----------------------------------------------------------+--------------
POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(50 75)
Multilinestring and polygon both 3d and 2d closest point
SELECT ST_AsEWKT(ST_3DClosestPoint(poly, mline)) As cp3d,
ST_AsEWKT(ST_ClosestPoint(poly, mline)) As cp2d
FROM (SELECT ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
(1 10 2, 5 20 1))') As mline ) As foo;
cp3d | cp2d
-------------------------------------------+--------------
POINT(39.993580415989 54.1889925532825 5) | POINT(20 40)
See Also
, , ,
ST_3DDistance
For geometry type Returns the 3-dimensional cartesian minimum distance (based on spatial ref) between two geometries in
projected units.
float ST_3DDistance
geometry
g1
geometry
g2
Description
For geometry type returns the 3-dimensional minimum cartesian distance between two geometries in
projected units (spatial ref units).
&Z_support;
&P_support;
&sqlmm_compliant; SQL-MM ?
&sfcgal_enhanced;
Availability: 2.0.0
Examples
-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
-- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
SELECT ST_3DDistance(
ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
) As dist_3d,
ST_Distance(
ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),2163),
ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),2163)
) As dist_2d;
dist_3d | dist_2d
------------------+-----------------
127.295059324629 | 126.66425605671
-- Multilinestring and polygon both 3d and 2d distance
-- Same example as 3D closest point example
SELECT ST_3DDistance(poly, mline) As dist3d,
ST_Distance(poly, mline) As dist2d
FROM (SELECT ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
(1 10 2, 5 20 1))') As mline ) As foo;
dist3d | dist2d
-------------------+--------
0.716635696066337 | 0
See Also
, , , , ,
ST_3DDWithin
For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units.
boolean ST_3DDWithin
geometry
g1
geometry
g2
double precision
distance_of_srid
Description
For geometry type returns true if the 3d distance between two objects is within distance_of_srid specified
projected units (spatial ref units).
&Z_support;
&P_support;
&sqlmm_compliant; SQL-MM ?
Availability: 2.0.0
Examples
-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
-- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
SELECT ST_3DDWithin(
ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
126.8
) As within_dist_3d,
ST_DWithin(
ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
126.8
) As within_dist_2d;
within_dist_3d | within_dist_2d
----------------+----------------
f | t
See Also
, , , ,
ST_3DDFullyWithin
Returns true if all of the 3D geometries are within the specified
distance of one another.
boolean ST_3DDFullyWithin
geometry
g1
geometry
g2
double precision
distance
Description
Returns true if the 3D geometries are fully within the specified distance
of one another. The distance is specified in units defined by the
spatial reference system of the geometries. For this function to make
sense, the source geometries must both be of the same coordinate projection,
having the same SRID.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries.
Availability: 2.0.0
&Z_support;
&P_support;
Examples
-- This compares the difference between fully within and distance within as well
-- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
(select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
------------------+-------------+------------------+------------------
f | t | t | f
See Also
, , ,
ST_3DIntersects
Returns TRUE if the Geometries "spatially
intersect" in 3d - only for points, linestrings, polygons, polyhedral surface (area). With SFCGAL backend enabled also supports TINS
boolean ST_3DIntersects
geometry
geomA
geometry
geomB
Description
Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned
returns true, then the geometries also spatially intersect.
Disjoint implies false for spatial intersection.
Availability: 2.0.0
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on the
geometries.
In order to take advantage of support for TINS, you need to enable the SFCGAL backend. This can be done at session time with: set postgis.backend = sfcgal;
or at the database or system level. Database level can be done with ALTER DATABASE gisdb SET postgis.backend = sfcgal;
.
&Z_support;
&P_support;
&T_support;
&sfcgal_enhanced;
&sqlmm_compliant; SQL-MM 3: ?
Geometry Examples
SELECT ST_3DIntersects(pt, line), ST_Intersects(pt,line)
FROM (SELECT 'POINT(0 0 2)'::geometry As pt,
'LINESTRING (0 0 1, 0 2 3 )'::geometry As line) As foo;
st_3dintersects | st_intersects
-----------------+---------------
f | t
(1 row)
TIN Examples
set postgis.backend = sfcgal;
SELECT ST_3DIntersects('TIN(((0 0,1 0,0 1,0 0)))'::geometry, 'POINT(.1 .1)'::geometry);
st_3dintersects
-----------------
t
See Also
ST_3DLongestLine
Returns the 3-dimensional longest line between two geometries
geometry ST_3DLongestLine
geometry
g1
geometry
g2
Description
Returns the 3-dimensional longest line between two geometries. The function will
only return the first longest line if more than one.
The line returned will always start in g1 and end in g2.
The 3D length of the line this function returns will always be the same as returns for g1 and g2.
Availability: 2.0.0
&Z_support;
&P_support;
Examples
linestring and point -- both 3d and 2d longest line
SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
) As foo;
lol3d_line_pt | lol2d_line_pt
-----------------------------------+----------------------------
LINESTRING(50 75 1000,100 100 30) | LINESTRING(98 190,100 100)
linestring and multipoint -- both 3d and 2d longest line
SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
) As foo;
lol3d_line_pt | lol2d_line_pt
---------------------------------+--------------------------
LINESTRING(98 190 1,50 74 1000) | LINESTRING(98 190,50 74)
Multilinestring and polygon both 3d and 2d longest line
SELECT ST_AsEWKT(ST_3DLongestLine(poly, mline)) As lol3d,
ST_AsEWKT(ST_LongestLine(poly, mline)) As lol2d
FROM (SELECT ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
(1 10 2, 5 20 1))') As mline ) As foo;
lol3d | lol2d
------------------------------+--------------------------
LINESTRING(175 150 5,1 10 2) | LINESTRING(175 150,1 10)
See Also
, , , ,
ST_3DMaxDistance
For geometry type Returns the 3-dimensional cartesian maximum distance (based on spatial ref) between two geometries in
projected units.
float ST_3DMaxDistance
geometry
g1
geometry
g2
Description
For geometry type returns the 3-dimensional maximum cartesian distance between two geometries in
projected units (spatial ref units).
&Z_support;
&P_support;
Availability: 2.0.0
Examples
-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
-- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
SELECT ST_3DMaxDistance(
ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
) As dist_3d,
ST_MaxDistance(
ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
) As dist_2d;
dist_3d | dist_2d
------------------+------------------
24383.7467488441 | 22247.8472107251
See Also
, , ,
ST_3DShortestLine
Returns the 3-dimensional shortest line between two geometries
geometry ST_3DShortestLine
geometry
g1
geometry
g2
Description
Returns the 3-dimensional shortest line between two geometries. The function will
only return the first shortest line if more than one, that the function finds.
If g1 and g2 intersects in just one point the function will return a line with both start
and end in that intersection-point.
If g1 and g2 are intersecting with more than one point the function will return a line with start
and end in the same point but it can be any of the intersecting points.
The line returned will always start in g1 and end in g2.
The 3D length of the line this function returns will always be the same as returns for g1 and g2.
Availability: 2.0.0
&Z_support;
&P_support;
Examples
linestring and point -- both 3d and 2d shortest line
SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
) As foo;
shl3d_line_pt | shl2d_line_pt
----------------------------------------------------------------------------+------------------------------------------------------
LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | LINESTRING(73.0769230769231 115.384615384615,100 100)
linestring and multipoint -- both 3d and 2d shortest line
SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
) As foo;
shl3d_line_pt | shl2d_line_pt
---------------------------------------------------------------------------+------------------------
LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | LINESTRING(50 75,50 74)
Multilinestring and polygon both 3d and 2d shortest line
SELECT ST_AsEWKT(ST_3DShortestLine(poly, mline)) As shl3d,
ST_AsEWKT(ST_ShortestLine(poly, mline)) As shl2d
FROM (SELECT ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
(1 10 2, 5 20 1))') As mline ) As foo;
shl3d | shl2d
---------------------------------------------------------------------------------------------------+------------------------
LINESTRING(39.993580415989 54.1889925532825 5,40.4078575708294 53.6052383805529 5.03423778139177) | LINESTRING(20 40,20 40)
See Also
, , , ,
ST_Area
Returns the area of the surface if it is a Polygon or
MultiPolygon. For geometry, a 2D Cartesian area is determined with units specified by the SRID. For geography, area is determined on a curved surface with units in square meters.
float ST_Area
geometry g1
float ST_Area
geography geog
boolean use_spheroid=true
Description
Returns the area of the geometry if it is a Polygon or
MultiPolygon. Return the area measurement of an ST_Surface or
ST_MultiSurface value. For geometry, a 2D Cartesian area is determined with units specified by the SRID. For geography, by default area is determined on a spheroid with units in square meters.
To measure around the faster but less accurate sphere, use ST_Area(geog,false).
Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced.
Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness.
&sfs_compliant;
&sqlmm_compliant; SQL-MM 3: 8.1.2, 9.5.3
&P_support;
For polyhedral surfaces, only supports 2D polyhedral surfaces (not 2.5D). For 2.5D, may give a non-zero answer, but only for the faces that
sit completely in XY plane.
&sfcgal_enhanced;
Examples
Return area in square feet for a plot of Massachusetts land and multiply by conversion to get square meters.
Note this is in square feet because EPSG:2249 is
Massachusetts State Plane Feet
SELECT ST_Area(the_geom) As sqft, ST_Area(the_geom)*POWER(0.3048,2) As sqm
FROM (SELECT
ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
743265 2967450,743265.625 2967416,743238 2967416))',2249) ) As foo(the_geom);
sqft | sqm
---------+-------------
928.625 | 86.27208552
Return area square feet and transform to Massachusetts state plane meters (EPSG:26986) to get square meters.
Note this is in square feet because 2249 is
Massachusetts State Plane Feet and transformed area is in square meters since EPSG:26986 is state plane Massachusetts meters
SELECT ST_Area(the_geom) As sqft, ST_Area(ST_Transform(the_geom,26986)) As sqm
FROM (SELECT
ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
743265 2967450,743265.625 2967416,743238 2967416))',2249) ) As foo(the_geom);
sqft | sqm
---------+------------------
928.625 | 86.2724304199219
Return area square feet and square meters using geography data type. Note that we transform to our geometry to geography
(before you can do that make sure your geometry is in WGS 84 long lat 4326). Geography always measures in meters.
This is just for demonstration to compare. Normally your table will be stored in geography data type already.
SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft_spheroid, ST_Area(the_geog,false)/POWER(0.3048,2) As sqft_sphere, ST_Area(the_geog) As sqm_spheroid
FROM (SELECT
geography(
ST_Transform(
ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))',
2249
) ,4326
)
)
) As foo(the_geog);
sqft_spheroid | sqft_sphere | sqm_spheroid
------------------+------------------+------------------
928.684403538925 | 927.049336105925 | 86.2776042893529
--if your data is in geography already
SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft, ST_Area(the_geog) As sqm
FROM somegeogtable;
See Also
, , ,
ST_Azimuth
Returns the north-based azimuth as the angle in radians measured clockwise from the vertical on pointA to pointB.
float ST_Azimuth
geometry pointA
geometry pointB
float ST_Azimuth
geography pointA
geography pointB
Description
Returns the azimuth in radians of the segment defined by the given
point geometries, or NULL if the two points are coincident. The azimuth is angle is referenced from north, and is positive clockwise: North = 0; East = π/2; South = π; West = 3π/2.
For the geography type, the forward azimuth is solved as part of the inverse geodesic problem.
The azimuth is mathematical concept defined as the angle between a reference plane and a point, with angular units in radians.
Units can be converted to degrees using a built-in PostgreSQL function degrees(), as shown in the example.
Availability: 1.1.0
Enhanced: 2.0.0 support for geography was introduced.
Enhanced: 2.2.0 measurement on spheroid performed with GeographicLib for improved accuracy and robustness.
Azimuth is especially useful in conjunction with ST_Translate for shifting an object along its perpendicular axis. See
upgis_lineshift Plpgsqlfunctions PostGIS wiki section for example of this.
Examples
Geometry Azimuth in degrees
SELECT degrees(ST_Azimuth(ST_Point(25, 45), ST_Point(75, 100))) AS degA_B,
degrees(ST_Azimuth(ST_Point(75, 100), ST_Point(25, 45))) AS degB_A;
dega_b | degb_a
------------------+------------------
42.2736890060937 | 222.273689006094
Green: the start Point(25,45) with its vertical. Yellow: degA_B as the path to travel (azimuth).
Green: the start Point(75,100) with its vertical. Yellow: degB_A as the path to travel (azimuth).
See Also
, , , PostgreSQL Math Functions
ST_Centroid
Returns the geometric center of a geometry.
geometry ST_Centroid
geometry
g1
Description
Computes the geometric center of a geometry, or equivalently,
the center of mass of the geometry as a POINT. For
[MULTI]POINTs, this is computed
as the arithmetic mean of the input coordinates. For
[MULTI]LINESTRINGs, this is
computed as the weighted length of each line segment. For
[MULTI]POLYGONs, "weight" is
thought in terms of area. If an empty geometry is supplied, an empty
GEOMETRYCOLLECTION is returned. If
NULL is supplied, NULL is
returned.
The centroid is equal to the centroid of the set of component
Geometries of highest dimension (since the lower-dimension geometries
contribute zero "weight" to the centroid).
Computation will be more accurate if performed by the GEOS
module (enabled at compile time).
&sfs_compliant;
&sqlmm_compliant; SQL-MM 3: 8.1.4, 9.5.5
Examples
In each of the following illustrations, the blue dot represents
the centroid of the source geometry.
Centroid of a
MULTIPOINT
Centroid of a
LINESTRING
Centroid of a
POLYGON
Centroid of a
GEOMETRYCOLLECTION
SELECT ST_AsText(ST_Centroid('MULTIPOINT ( -1 0, -1 2, -1 3, -1 4, -1 7, 0 1, 0 3, 1 1, 2 0, 6 0, 7 8, 9 8, 10 6 )'));
st_astext
------------------------------------------
POINT(2.30769230769231 3.30769230769231)
(1 row)
See Also
ST_ClosestPoint
Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of
the shortest line.
geometry ST_ClosestPoint
geometry
g1
geometry
g2
Description
Returns the 2-dimensional point on g1 that is closest to g2. This is the first point of
the shortest line.
If you have a 3D Geometry, you may prefer to use .
Availability: 1.5.0
Examples
Closest between point and linestring is the point itself, but closest
point between a linestring and point is the point on line string that is closest.
SELECT ST_AsText(ST_ClosestPoint(pt,line)) AS cp_pt_line,
ST_AsText(ST_ClosestPoint(line,pt)) As cp_line_pt
FROM (SELECT 'POINT(100 100)'::geometry As pt,
'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry As line
) As foo;
cp_pt_line | cp_line_pt
----------------+------------------------------------------
POINT(100 100) | POINT(73.0769230769231 115.384615384615)
closest point on polygon A to polygon B
SELECT ST_AsText(
ST_ClosestPoint(
ST_GeomFromText('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'),
ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
)
) As ptwkt;
ptwkt
------------------------------------------
POINT(140.752120669087 125.695053378061)
See Also
,, , ,
ST_Contains
Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.
boolean ST_Contains
geometry
geomA
geometry
geomB
Description
Geometry A contains Geometry B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.
An important subtlety of this definition is that A does not contain its boundary, but A does contain itself. Contrast that to where geometry
A does not Contain Properly itself.
Returns TRUE if geometry B is completely inside geometry A. For this function to make
sense, the source geometries must both be of the same coordinate projection,
having the same SRID. ST_Contains is the inverse of ST_Within. So ST_Contains(A,B) implies ST_Within(B,A) except in the case of
invalid geometries where the result is always false regardless or not defined.
Performed by the GEOS module
Do not call with a GEOMETRYCOLLECTION as an argument
Do not use this function with invalid geometries. You will get unexpected results.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_Contains.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
&sfs_compliant; s2.1.1.2 // s2.1.13.3
- same as within(geometry B, geometry A)
&sqlmm_compliant; SQL-MM 3: 5.1.31
There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
For details check out Subtleties of OGC Covers, Contains, Within
Examples
The ST_Contains predicate returns TRUE in all the following illustrations.
LINESTRING / MULTIPOINT
POLYGON / POINT
POLYGON / LINESTRING
POLYGON / POLYGON
The ST_Contains predicate returns FALSE in all the following illustrations.
POLYGON / MULTIPOINT
POLYGON / LINESTRING
-- A circle within a circle
SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
ST_Contains(bigc,smallc) As bigcontainssmall,
ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
-- Result
smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
f | t | t | t | t | f
-- Example demonstrating difference between contains and contains properly
SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
( ST_Point(1,1) )
) As foo(geomA);
geomtype | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon | t | f | f | f
ST_LineString | t | f | f | f
ST_Point | t | t | f | f
See Also
, , , , ,
ST_ContainsProperly
Returns true if B intersects the interior of A but not the boundary (or exterior). A does not contain properly itself, but does contain itself.
boolean ST_ContainsProperly
geometry
geomA
geometry
geomB
Description
Returns true if B intersects the interior of A but not the boundary (or exterior).
A does not contain properly itself, but does contain itself.
Every point of the other geometry is a point of this geometry's interior. The DE-9IM Intersection Matrix for the two geometries matches
[T**FF*FF*] used in
From JTS docs slightly reworded: The advantage to using this predicate over and is that it can be computed
efficiently, with no need to compute topology at individual points.
An example use case for this predicate is computing the intersections
of a set of geometries with a large polygonal geometry.
Since intersection is a fairly slow operation, it can be more efficient
to use containsProperly to filter out test geometries which lie
wholly inside the area. In these cases the intersection is
known a priori to be exactly the original test geometry.
Availability: 1.4.0 - requires GEOS >= 3.1.0.
Do not call with a GEOMETRYCOLLECTION as an argument
Do not use this function with invalid geometries. You will get unexpected results.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_ContainsProperly.
Examples
--a circle within a circle
SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
--Result
smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
f | t | f | t | t | f
--example demonstrating difference between contains and contains properly
SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
( ST_Point(1,1) )
) As foo(geomA);
geomtype | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon | t | f | f | f
ST_LineString | t | f | f | f
ST_Point | t | t | f | f
See Also
, , , , , , ,
ST_Covers
Returns 1 (TRUE) if no point in Geometry B is outside
Geometry A
boolean ST_Covers
geometry
geomA
geometry
geomB
boolean ST_Covers
geography
geogpolyA
geography
geogpointB
Description
Returns 1 (TRUE) if no point in Geometry/Geography B is outside
Geometry/Geography A
Performed by the GEOS module
Do not call with a GEOMETRYCOLLECTION as an argument
For geography only Polygon covers point is supported.
Do not use this function with invalid geometries. You will get unexpected results.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_Covers.
Availability: 1.2.2 - requires GEOS >= 3.0
Availability: 1.5 - support for geography was introduced.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
Not an OGC standard, but Oracle has it too.
There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
For details check out Subtleties of OGC Covers, Contains, Within
Examples
Geometry example
--a circle covering a circle
SELECT ST_Covers(smallc,smallc) As smallinsmall,
ST_Covers(smallc, bigc) As smallcoversbig,
ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
--Result
smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior
--------------+----------------+-------------------+---------------------
t | f | t | f
(1 row)
Geeography Example
-- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer
SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,
ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent
FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly,
ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo;
poly_covers_pt | buff_10m_covers_cent
----------------+------------------
f | t
See Also
, ,
ST_CoveredBy
Returns 1 (TRUE) if no point in Geometry/Geography A is outside
Geometry/Geography B
boolean ST_CoveredBy
geometry
geomA
geometry
geomB
boolean ST_CoveredBy
geography
geogA
geography
geogB
Description
Returns 1 (TRUE) if no point in Geometry/Geography A is outside
Geometry/Geography B
Performed by the GEOS module
Do not call with a GEOMETRYCOLLECTION as an argument
Do not use this function with invalid geometries. You will get unexpected results.
Availability: 1.2.2 - requires GEOS >= 3.0
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_CoveredBy.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
Not an OGC standard, but Oracle has it too.
There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
For details check out Subtleties of OGC Covers, Contains, Within
Examples
--a circle coveredby a circle
SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
--Result
smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
--------------+-------------------+----------------------+------------------
t | t | t | f
(1 row)
See Also
, , ,
ST_Crosses
Returns TRUE if the supplied geometries have some, but not all,
interior points in common.
boolean ST_Crosses
geometry g1
geometry g2
Description
ST_Crosses takes two geometry objects and
returns TRUE if their intersection "spatially cross", that is, the
geometries have some, but not all interior points in common. The
intersection of the interiors of the geometries must not be the empty
set and must have a dimensionality less than the the maximum dimension
of the two input geometries. Additionally, the intersection of the two
geometries must not equal either of the source geometries. Otherwise, it
returns FALSE.
In mathematical terms, this is expressed as:
TODO: Insert appropriate MathML markup here or use a gif.
Simple HTML markup does not work well in both IE and Firefox.
The DE-9IM Intersection Matrix for the two geometries is:
T*T****** (for Point/Line, Point/Area, and
Line/Area situations)
T*****T** (for Line/Point, Area/Point, and
Area/Line situations)
0******** (for Line/Line situations)
For any other combination of dimensions this predicate returns
false.
The OpenGIS Simple Features Specification defines this predicate
only for Point/Line, Point/Area, Line/Line, and Line/Area situations.
JTS / GEOS extends the definition to apply to Line/Point, Area/Point and
Area/Line situations as well. This makes the relation
symmetric.
Do not call with a GEOMETRYCOLLECTION as an argument
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on the
geometries.
&sfs_compliant; s2.1.13.3
&sqlmm_compliant; SQL-MM 3: 5.1.29
Examples
The following illustrations all return TRUE.
MULTIPOINT / LINESTRING
MULTIPOINT / POLYGON
LINESTRING / POLYGON
LINESTRING / LINESTRING
Consider a situation where a user has two tables: a table of roads
and a table of highways.
CREATE TABLE roads (
id serial NOT NULL,
the_geom geometry,
CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);
CREATE TABLE highways (
id serial NOT NULL,
the_gem geometry,
CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);
To determine a list of roads that cross a highway, use a query
similiar to:
SELECT roads.id
FROM roads, highways
WHERE ST_Crosses(roads.the_geom, highways.the_geom);
ST_LineCrossingDirection
Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing.
integer ST_LineCrossingDirection
geometry linestringA
geometry linestringB
Description
Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing. This is only supported for LINESTRING
Definition of integer constants is as follows:
0: LINE NO CROSS
-1: LINE CROSS LEFT
1: LINE CROSS RIGHT
-2: LINE MULTICROSS END LEFT
2: LINE MULTICROSS END RIGHT
-3: LINE MULTICROSS END SAME FIRST LEFT
3: LINE MULTICROSS END SAME FIRST RIGHT
Availability: 1.4
Examples
Line 1 (green), Line 2 ball is start point,
triangle are end points. Query below.
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As line2
) As foo;
l1_cross_l2 | l2_cross_l1
-------------+-------------
3 | -3
Line 1 (green), Line 2 (blue) ball is start point,
triangle are end points. Query below.
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
ST_GeomFromText('LINESTRING (171 154, 20 140, 71 74, 2.99 90.16)') As line2
) As foo;
l1_cross_l2 | l2_cross_l1
-------------+-------------
2 | -2
Line 1 (green), Line 2 (blue) ball is start point,
triangle are end points. Query below.
SELECT
ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As line2
) As foo;
l1_cross_l2 | l2_cross_l1
-------------+-------------
-1 | 1
Line 1 (green), Line 2 (blue) ball is start point,
triangle are end points. Query below.
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
ST_GeomFromText('LINESTRING(2.99 90.16,71 74,20 140,171 154)') As line2
) As foo;
l1_cross_l2 | l2_cross_l1
-------------+-------------
-2 | 2
SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)
FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom && s2.the_geom )
WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;
See Also
ST_Disjoint
Returns TRUE if the Geometries do not "spatially
intersect" - if they do not share any space together.
boolean ST_Disjoint
geometry
A
geometry
B
Description
Overlaps, Touches, Within all imply geometries are not spatially disjoint. If any of the aforementioned
returns true, then the geometries are not spatially disjoint.
Disjoint implies false for spatial intersection.
Do not call with a GEOMETRYCOLLECTION as an argument
Performed by the GEOS module
This function call does not use indexes
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
&sfs_compliant; s2.1.1.2 //s2.1.13.3
- a.Relate(b, 'FF*FF****')
&sqlmm_compliant; SQL-MM 3: 5.1.26
Examples
SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
st_disjoint
---------------
t
(1 row)
SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
st_disjoint
---------------
f
(1 row)
See Also
ST_Intersects
ST_Distance
For geometry type Returns the 2D Cartesian distance between two geometries in
projected units (based on spatial ref). For geography type defaults to return minimum geodesic distance between two geographies in meters.
float ST_Distance
geometry
g1
geometry
g2
float ST_Distance
geography
gg1
geography
gg2
float ST_Distance
geography
gg1
geography
gg2
boolean
use_spheroid
Description
For geometry type returns the minimum 2D Cartesian distance between two geometries in
projected units (spatial ref units). For geography type defaults to return the minimum geodesic distance between two geographies in meters. If use_spheroid is
false, a faster sphere calculation is used instead of a spheroid.
&sfs_compliant;
&sqlmm_compliant; SQL-MM 3: 5.1.23
&curve_support;
&sfcgal_enhanced;
Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertex geometries
Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.
Enhanced: 2.1.0 - support for curved geometries was introduced.
Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness.
Basic Geometry Examples
--Geometry example - units in planar degrees 4326 is WGS 84 long lat unit=degrees
SELECT ST_Distance(
ST_GeomFromText('POINT(-72.1235 42.3521)',4326),
ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326)
);
st_distance
-----------------
0.00150567726382282
-- Geometry example - units in meters (SRID: 26986 Massachusetts state plane meters) (most accurate for Massachusetts)
SELECT ST_Distance(
ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),26986),
ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),26986)
);
st_distance
-----------------
123.797937878454
-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (least accurate)
SELECT ST_Distance(
ST_Transform(ST_GeomFromText('POINT(-72.1235 42.3521)',4326),2163),
ST_Transform(ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326),2163)
);
st_distance
------------------
126.664256056812
Geography Examples
-- same as geometry example but note units in meters - use sphere for slightly faster less accurate
SELECT ST_Distance(gg1, gg2) As spheroid_dist, ST_Distance(gg1, gg2, false) As sphere_dist
FROM (SELECT
ST_GeographyFromText('SRID=4326;POINT(-72.1235 42.3521)') As gg1,
ST_GeographyFromText('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)') As gg2
) As foo ;
spheroid_dist | sphere_dist
------------------+------------------
123.802076746848 | 123.475736916397
See Also
, , , , ,
ST_HausdorffDistance
Returns the Hausdorff distance between two geometries. Basically a measure of how similar or dissimilar 2 geometries are. Units are in the units of the spatial
reference system of the geometries.
float ST_HausdorffDistance
geometry
g1
geometry
g2
float ST_HausdorffDistance
geometry
g1
geometry
g2
float
densifyFrac
Description
Implements algorithm for computing a distance metric which can be thought of as the "Discrete Hausdorff Distance".
This is the Hausdorff distance restricted to discrete points for one of the geometries. Wikipedia article on Hausdorff distance
Martin Davis note on how Hausdorff Distance calculation was used to prove correctness of the CascadePolygonUnion approach.
When densifyFrac is specified, this function performs a segment densification before computing the discrete hausdorff distance. The densifyFrac parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.
The current implementation supports only vertices as the discrete locations. This could be extended to allow an arbitrary density of points to be used.
This algorithm is NOT equivalent to the standard Hausdorff distance. However, it computes an approximation that is correct for a large subset of useful cases.
One important part of this subset is Linestrings that are roughly parallel to each other, and roughly equal in length. This is a useful metric for line matching.
Availability: 1.5.0 - requires GEOS >= 3.2.0
Examples
For each building, find the parcel that best represents it. First we require the parcel intersect with the geometry.
DISTINCT ON guarantees we get each building listed only once, the ORDER BY .. ST_HausdorffDistance gives us a preference of parcel that is most similar to the building.
SELECT DISTINCT ON(buildings.gid) buildings.gid, parcels.parcel_id
FROM buildings INNER JOIN parcels ON ST_Intersects(buildings.geom,parcels.geom)
ORDER BY buildings.gid, ST_HausdorffDistance(buildings.geom, parcels.geom);
postgis=# SELECT ST_HausdorffDistance(
'LINESTRING (0 0, 2 0)'::geometry,
'MULTIPOINT (0 1, 1 0, 2 1)'::geometry);
st_hausdorffdistance
----------------------
1
(1 row)
postgis=# SELECT st_hausdorffdistance('LINESTRING (130 0, 0 0, 0 150)'::geometry, 'LINESTRING (10 10, 10 150, 130 10)'::geometry, 0.5);
st_hausdorffdistance
----------------------
70
(1 row)
ST_MaxDistance
Returns the 2-dimensional largest distance between two geometries in
projected units.
float ST_MaxDistance
geometry g1
geometry g2
Description
Returns the 2-dimensional maximum distance between two geometries in
projected units. If g1 and g2 is the same geometry the function will return the distance between
the two vertices most far from each other in that geometry.
Availability: 1.5.0
Examples
Basic furthest distance the point is to any part of the line
postgis=# SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
st_maxdistance
-----------------
2
(1 row)
postgis=# SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 2, 2 2 )'::geometry);
st_maxdistance
------------------
2.82842712474619
(1 row)
See Also
, ,
ST_DistanceSphere
Returns minimum distance in meters between two lon/lat
geometries. Uses a spherical earth and radius derived from the spheroid
defined by the SRID.
Faster than ST_DistanceSpheroid , but less
accurate. PostGIS versions prior to 1.5 only implemented for points.
float ST_DistanceSphere
geometry geomlonlatA
geometry geomlonlatB
Description
Returns minimum distance in meters between two lon/lat
points. Uses a spherical earth and radius derived from the spheroid
defined by the SRID.
Faster than , but less
accurate. PostGIS Versions prior to 1.5 only implemented for points.
Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.
Changed: 2.2.0 In prior versions this used to be called ST_Distance_Sphere
Examples
SELECT round(CAST(ST_DistanceSphere(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters,
round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),
ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters,
round(CAST(ST_Distance(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)', 4326)) As numeric),5) As dist_degrees,
round(CAST(ST_Distance(ST_Transform(the_geom,32611),
ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As min_dist_line_point_meters
FROM
(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As the_geom) as foo;
dist_meters | dist_utm11_meters | dist_degrees | min_dist_line_point_meters
-------------+-------------------+--------------+----------------------------
70424.47 | 70438.00 | 0.72900 | 65871.18
See Also
,
ST_DistanceSpheroid
Returns the minimum distance between two lon/lat geometries given a
particular spheroid.
PostGIS versions prior to 1.5 only support points.
float ST_DistanceSpheroid
geometry geomlonlatA
geometry geomlonlatB
spheroid measurement_spheroid
Description
Returns minimum distance in meters between two lon/lat
geometries given a particular spheroid. See the explanation of spheroids given for
. PostGIS version prior to 1.5 only support points.
This function currently does not look at the SRID of a geometry and will always assume its represented in the coordinates of the passed in spheroid. Prior versions of this function only support points.
Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.
Changed: 2.2.0 In prior versions this used to be called ST_Distance_Spheroid
Examples
SELECT round(CAST(
ST_DistanceSpheroid(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326), 'SPHEROID["WGS 84",6378137,298.257223563]')
As numeric),2) As dist_meters_spheroid,
round(CAST(ST_DistanceSphere(ST_Centroid(the_geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters_sphere,
round(CAST(ST_Distance(ST_Transform(ST_Centroid(the_geom),32611),
ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters
FROM
(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As the_geom) as foo;
dist_meters_spheroid | dist_meters_sphere | dist_utm11_meters
----------------------+--------------------+-------------------
70454.92 | 70424.47 | 70438.00
See Also
,
ST_DFullyWithin
Returns true if all of the geometries are within the specified
distance of one another
boolean ST_DFullyWithin
geometry
g1
geometry
g2
double precision
distance
Description
Returns true if the geometries is fully within the specified distance
of one another. The distance is specified in units defined by the
spatial reference system of the geometries. For this function to make
sense, the source geometries must both be of the same coordinate projection,
having the same SRID.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries.
Availability: 1.5.0
Examples
postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from
(select ST_GeomFromText('POINT(1 1)') as geom_a,ST_GeomFromText('LINESTRING(1 5, 2 7, 1 9, 14 12)') as geom_b) t1;
-----------------
DFullyWithin10 | DWithin10 | DFullyWithin20 |
---------------+----------+---------------+
f | t | t |
See Also
,
ST_DWithin
Returns true if the geometries are within the specified
distance of one another. For geometry units are in those of spatial reference and For geography units are in meters and measurement is
defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.
boolean ST_DWithin
geometry
g1
geometry
g2
double precision
distance_of_srid
boolean ST_DWithin
geography
gg1
geography
gg2
double precision
distance_meters
boolean ST_DWithin
geography
gg1
geography
gg2
double precision
distance_meters
boolean
use_spheroid
Description
Returns true if the geometries are within the specified distance
of one another.
For Geometries: The distance is specified in units defined by the
spatial reference system of the geometries. For this function to make
sense, the source geometries must both be of the same coordinate projection,
having the same SRID.
For geography units are in meters and measurement is
defaulted to use_spheroid=true, for faster check, use_spheroid=false to measure along sphere.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries.
Prior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to
achieve the same effect and in pre-1.3.4 this function was basically short-hand for that construct.
From 1.3.4, ST_DWithin uses a more short-circuit distance function which should make it more efficient
than prior versions for larger buffer regions.
Use ST_3DDWithin if you have 3D geometries.
&sfs_compliant;
Availability: 1.5.0 support for geography was introduced
Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.
Enhanced: 2.1.0 support for curved geometries was introduced.
Examples
--Find the nearest hospital to each school
--that is within 3000 units of the school.
-- We do an ST_DWithin search to utilize indexes to limit our search list
-- that the non-indexable ST_Distance needs to process
--If the units of the spatial reference is meters then units would be meters
SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.the_geom, h.hospital_name
FROM schools s
LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)
ORDER BY s.gid, ST_Distance(s.the_geom, h.the_geom);
--The schools with no close hospitals
--Find all schools with no hospital within 3000 units
--away from the school. Units is in units of spatial ref (e.g. meters, feet, degrees)
SELECT s.gid, s.school_name
FROM schools s
LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)
WHERE h.gid IS NULL;
See Also
,
ST_Equals
Returns true if the given geometries represent the same geometry. Directionality
is ignored.
boolean ST_Equals
geometry A
geometry B
Description
Returns TRUE if the given Geometries are "spatially
equal". Use this for a 'better' answer than '='.
Note by spatially equal we mean ST_Within(A,B) = true and ST_Within(B,A) = true and
also mean ordering of points can be different but
represent the same geometry structure. To verify the order of points is consistent, use
ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of
points are the same).
This function will return false if either geometry is invalid even if they are binary equal.
&sfs_compliant; s2.1.1.2
&sqlmm_compliant; SQL-MM 3: 5.1.24
Examples
SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
st_equals
-----------
t
(1 row)
SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
st_equals
-----------
t
(1 row)
See Also
, , ,
ST_HasArc
Returns true if a geometry or geometry collection contains a circular string
boolean ST_HasArc
geometry geomA
Description
Returns true if a geometry or geometry collection contains a circular string
Availability: 1.2.3?
&Z_support;
&curve_support;
Examples
SELECT ST_HasArc(ST_Collect('LINESTRING(1 2, 3 4, 5 6)', 'CIRCULARSTRING(1 1, 2 3, 4 5, 6 7, 5 6)'));
st_hasarc
--------
t
See Also
,
ST_Intersects
Returns TRUE if the Geometries/Geography "spatially
intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint).
For geography -- tolerance is 0.00001 meters (so any points that close are considered to intersect)
boolean ST_Intersects
geometry
geomA
geometry
geomB
boolean ST_Intersects
geography
geogA
geography
geogB
Description
If a geometry or geography shares any portion of space then they intersect.
For geography -- tolerance is 0.00001 meters (so any points that are close are considered to intersect)
Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned
returns true, then the geometries also spatially intersect.
Disjoint implies false for spatial intersection.
Do not call with a GEOMETRYCOLLECTION as an argument for geometry version. The geography
version supports GEOMETRYCOLLECTION since its a thin wrapper around distance implementation.
Performed by the GEOS module (for geometry), geography is native
Availability: 1.5 support for geography was introduced.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on the
geometries.
For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather
than spheroid calculation.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
&sfs_compliant; s2.1.1.2 //s2.1.13.3
- ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))
&sqlmm_compliant; SQL-MM 3: 5.1.27
&sfcgal_enhanced;
Geometry Examples
SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
st_intersects
---------------
f
(1 row)
SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
st_intersects
---------------
t
(1 row)
Geography Examples
SELECT ST_Intersects(
ST_GeographyFromText('SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'),
ST_GeographyFromText('SRID=4326;POINT(-43.23456 72.4567772)')
);
st_intersects
---------------
t
See Also
,
ST_Length
Returns the 2D length of the geometry if it is a LineString or MultiLineString. geometry are in units of spatial reference and geography are in meters (default spheroid)
float ST_Length
geometry a_2dlinestring
float ST_Length
geography geog
boolean use_spheroid=true
Description
For geometry: Returns the 2D Cartesian length of the geometry if it is a LineString, MultiLineString, ST_Curve, ST_MultiCurve. 0 is returned for
areal geometries. For areal geometries use . For geometry types, units for length measures are specified by the
spatial reference system of the geometry.
For geography types, the calculations are performed using the inverse geodesic problem, where length units are in meters.
If PostGIS is compiled with PROJ version 4.8.0 or later, the spheroid is specified by the SRID, otherwise it is exclusive to WGS84.
If use_spheroid=false, then calculations will approximate a sphere instead of a spheroid.
Currently for geometry this is an alias for ST_Length2D, but this may change to support higher dimensions.
Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0
this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon
For geography measurement defaults spheroid measurement. To use the faster less accurate sphere use ST_Length(gg,false);
&sfs_compliant; s2.1.5.1
&sqlmm_compliant; SQL-MM 3: 7.1.2, 9.3.4
Availability: 1.5.0 geography support was introduced in 1.5.
&sfcgal_enhanced;
Geometry Examples
Return length in feet for line string. Note this is in feet because EPSG:2249 is
Massachusetts State Plane Feet
SELECT ST_Length(ST_GeomFromText('LINESTRING(743238 2967416,743238 2967450,743265 2967450,
743265.625 2967416,743238 2967416)',2249));
st_length
---------
122.630744000095
--Transforming WGS 84 LineString to Massachusetts state plane meters
SELECT ST_Length(
ST_Transform(
ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)'),
26986
)
);
st_length
---------
34309.4563576191
Geography Examples
Return length of WGS 84 geography line
-- default calculation is using a sphere rather than spheroid
SELECT ST_Length(the_geog) As length_spheroid, ST_Length(the_geog,false) As length_sphere
FROM (SELECT ST_GeographyFromText(
'SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)') As the_geog)
As foo;
length_spheroid | length_sphere
------------------+------------------
34310.5703627288 | 34346.2060960742
See Also
, , , ,
ST_Length2D
Returns the 2-dimensional length of the geometry if it is a
linestring or multi-linestring. This is an alias for ST_Length
float ST_Length2D
geometry a_2dlinestring
Description
Returns the 2-dimensional length of the geometry if it is a
linestring or multi-linestring. This is an alias for ST_Length
See Also
,
ST_3DLength
Returns the 3-dimensional or 2-dimensional length of the geometry if it is a
linestring or multi-linestring.
float ST_3DLength
geometry a_3dlinestring
Description
Returns the 3-dimensional or 2-dimensional length of the geometry if it is a
linestring or multi-linestring. For 2-d lines it will just return the 2-d length (same as ST_Length and ST_Length2D)
&Z_support;
Changed: 2.0.0 In prior versions this used to be called ST_Length3D
Examples
Return length in feet for a 3D cable. Note this is in feet because EPSG:2249 is
Massachusetts State Plane Feet
SELECT ST_3DLength(ST_GeomFromText('LINESTRING(743238 2967416 1,743238 2967450 1,743265 2967450 3,
743265.625 2967416 3,743238 2967416 3)',2249));
ST_3DLength
-----------
122.704716741457
See Also
,
ST_LengthSpheroid
Calculates the 2D or 3D length of a linestring/multilinestring on an ellipsoid. This
is useful if the coordinates of the geometry are in
longitude/latitude and a length is desired without reprojection.
float ST_LengthSpheroid
geometry a_linestring
spheroid a_spheroid
Description
Calculates the length of a geometry on an ellipsoid. This
is useful if the coordinates of the geometry are in
longitude/latitude and a length is desired without reprojection.
The ellipsoid is a separate database type and can be constructed
as follows:
SPHEROID[<NAME>,<SEMI-MAJOR
AXIS>,<INVERSE FLATTENING>]
SPHEROID["GRS_1980",6378137,298.257222101]
Will return 0 for anything that is not a MULTILINESTRING or LINESTRING
Availability: 1.2.2
Changed: 2.2.0 In prior versions this used to be called ST_Length_Spheroid and used to have a ST_3DLength_Spheroid alias
&Z_support;
Examples
SELECT ST_LengthSpheroid( geometry_column,
'SPHEROID["GRS_1980",6378137,298.257222101]' )
FROM geometry_table;
SELECT ST_LengthSpheroid( the_geom, sph_m ) As tot_len,
ST_LengthSpheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
ST_LengthSpheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
(-71.05957 42.3589 , -71.061 43))') As the_geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m) as foo;
tot_len | len_line1 | len_line2
------------------+------------------+------------------
85204.5207562955 | 13986.8725229309 | 71217.6482333646
--3D
SELECT ST_LengthSpheroid( the_geom, sph_m ) As tot_len,
ST_LengthSpheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
ST_LengthSpheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
(-71.05957 42.3589 75, -71.061 43 90))') As the_geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m) as foo;
tot_len | len_line1 | len_line2
------------------+-----------------+------------------
85204.5259107402 | 13986.876097711 | 71217.6498130292
See Also
,
ST_Length2D_Spheroid
Calculates the 2D length of a linestring/multilinestring on an ellipsoid. This
is useful if the coordinates of the geometry are in
longitude/latitude and a length is desired without reprojection.
float ST_Length2D_Spheroid
geometry a_linestring
spheroid a_spheroid
Description
Calculates the 2D length of a geometry on an ellipsoid. This
is useful if the coordinates of the geometry are in
longitude/latitude and a length is desired without reprojection.
The ellipsoid is a separate database type and can be constructed
as follows:
SPHEROID[<NAME>,<SEMI-MAJOR
AXIS>,<INVERSE FLATTENING>]
SPHEROID["GRS_1980",6378137,298.257222101]
Will return 0 for anything that is not a MULTILINESTRING or LINESTRING
This is much like except it will throw away the Z coordinate in calculations.
Examples
SELECT ST_Length2D_Spheroid( geometry_column,
'SPHEROID["GRS_1980",6378137,298.257222101]' )
FROM geometry_table;
SELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,
ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
(-71.05957 42.3589 , -71.061 43))') As the_geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m) as foo;
tot_len | len_line1 | len_line2
------------------+------------------+------------------
85204.5207562955 | 13986.8725229309 | 71217.6482333646
--3D Observe same answer
SELECT ST_Length2D_Spheroid( the_geom, sph_m ) As tot_len,
ST_Length2D_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,
ST_Length2D_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2
FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
(-71.05957 42.3589 75, -71.061 43 90))') As the_geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m) as foo;
tot_len | len_line1 | len_line2
------------------+------------------+------------------
85204.5207562955 | 13986.8725229309 | 71217.6482333646
See Also
,
ST_LongestLine
Returns the 2-dimensional longest line points of two geometries.
The function will only return the first longest line if more than one, that the function finds.
The line returned will always start in g1 and end in g2.
The length of the line this function returns will always be the same as st_maxdistance returns for g1 and g2.
geometry ST_LongestLine
geometry
g1
geometry
g2
Description
Returns the 2-dimensional longest line between the points of two geometries.
Availability: 1.5.0
Examples
Longest line between point and line
SELECT ST_AsText(
ST_LongestLine('POINT(100 100)'::geometry,
'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry)
) As lline;
lline
-----------------
LINESTRING(100 100,98 190)
longest line between polygon and polygon
SELECT ST_AsText(
ST_LongestLine(
ST_GeomFromText('POLYGON((175 150, 20 40,
50 60, 125 100, 175 150))'),
ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
)
) As llinewkt;
lline
-----------------
LINESTRING(20 40,121.111404660392 186.629392246051)
longest straight distance to travel from one part of an elegant city to the other
Note the max distance = to the length of the line.
SELECT ST_AsText(ST_LongestLine(c.the_geom, c.the_geom)) As llinewkt,
ST_MaxDistance(c.the_geom,c.the_geom) As max_dist,
ST_Length(ST_LongestLine(c.the_geom, c.the_geom)) As lenll
FROM (SELECT ST_BuildArea(ST_Collect(the_geom)) As the_geom
FROM (SELECT ST_Translate(ST_SnapToGrid(ST_Buffer(ST_Point(50 ,generate_series(50,190, 50)
),40, 'quad_segs=2'),1), x, 0) As the_geom
FROM generate_series(1,100,50) As x) AS foo
) As c;
llinewkt | max_dist | lenll
---------------------------+------------------+------------------
LINESTRING(23 22,129 178) | 188.605408193933 | 188.605408193933
See Also
, ,
ST_OrderingEquals
Returns true if the given geometries represent the same geometry
and points are in the same directional order.
boolean ST_OrderingEquals
geometry A
geometry B
Description
ST_OrderingEquals compares two geometries and returns t (TRUE) if the
geometries are equal and the coordinates are in the same order;
otherwise it returns f (FALSE).
This function is implemented as per the ArcSDE SQL
specification rather than SQL-MM.
http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals
&sqlmm_compliant; SQL-MM 3: 5.1.43
Examples
SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
st_orderingequals
-----------
f
(1 row)
SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
st_orderingequals
-----------
t
(1 row)
SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
st_orderingequals
-----------
f
(1 row)
See Also
,
ST_Overlaps
Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained by each other.
boolean ST_Overlaps
geometry A
geometry B
Description
Returns TRUE if the Geometries "spatially
overlap". By that we mean they intersect, but one does not completely contain another.
Performed by the GEOS module
Do not call with a GeometryCollection as an argument
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_Overlaps.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
&sfs_compliant; s2.1.1.2 // s2.1.13.3
&sqlmm_compliant; SQL-MM 3: 5.1.32
Examples
The following illustrations all return TRUE.
MULTIPOINT / MULTIPOINT
LINESTRING / LINESTRING
POLYGON / POLYGON
--a point on a line is contained by the line and is of a lower dimension, and therefore does not overlap the line
nor crosses
SELECT ST_Overlaps(a,b) As a_overlap_b,
ST_Crosses(a,b) As a_crosses_b,
ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a
FROM (SELECT ST_GeomFromText('POINT(1 0.5)') As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)') As b)
As foo
a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a
------------+-------------+----------------+--------------
f | f | t | t
--a line that is partly contained by circle, but not fully is defined as intersecting and crossing,
-- but since of different dimension it does not overlap
SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,
ST_Intersects(a, b) As a_intersects_b,
ST_Contains(a,b) As a_contains_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3) As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)') As b)
As foo;
a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b
-------------+-------------+----------------+--------------
f | t | t | f
-- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,
-- but is not fully contained by the circle is defined as overlapping since they are of the same dimension,
-- but it does not cross, because the intersection of the 2 is of the same dimension
-- as the maximum dimension of the 2
SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) As a_intersects_b,
ST_Contains(b,a) As b_contains_a,
ST_Dimension(a) As dim_a, ST_Dimension(b) as dim_b, ST_Dimension(ST_Intersection(a,b)) As dima_intersection_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3) As a,
ST_Buffer(ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)'),0.5) As b)
As foo;
a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | dima_intersection_b
-------------+-------------+----------------+--------------+-------+-------+---------------------
t | f | t | f | 2 | 2 | 2
See Also
, , ,
ST_Perimeter
Return the length measurement of the boundary of an ST_Surface
or ST_MultiSurface geometry or geography. (Polygon, MultiPolygon). geometry measurement is in units of spatial reference and geography is in meters.
float ST_Perimeter
geometry g1
float ST_Perimeter
geography geog
boolean use_spheroid=true
Description
Returns the 2D perimeter of the geometry/geography if it is a ST_Surface, ST_MultiSurface (Polygon, MultiPolygon). 0 is returned for
non-areal geometries. For linear geometries use . For geometry types, units for perimeter measures are specified by the
spatial reference system of the geometry.
For geography types, the calculations are performed using the inverse geodesic problem, where perimeter units are in meters.
If PostGIS is compiled with PROJ version 4.8.0 or later, the spheroid is specified by the SRID, otherwise it is exclusive to WGS84.
If use_spheroid=false, then calculations will approximate a sphere instead of a spheroid.
Currently this is an alias for ST_Perimeter2D, but this may change to support higher dimensions.
&sfs_compliant; s2.1.5.1
&sqlmm_compliant; SQL-MM 3: 8.1.3, 9.5.4
Availability 2.0.0: Support for geography was introduced
Examples: Geometry
Return perimeter in feet for Polygon and MultiPolygon. Note this is in feet because EPSG:2249 is
Massachusetts State Plane Feet
SELECT ST_Perimeter(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,743265 2967450,
743265.625 2967416,743238 2967416))', 2249));
st_perimeter
---------
122.630744000095
(1 row)
SELECT ST_Perimeter(ST_GeomFromText('MULTIPOLYGON(((763104.471273676 2949418.44119003,
763104.477769673 2949418.42538203,
763104.189609677 2949418.22343004,763104.471273676 2949418.44119003)),
((763104.471273676 2949418.44119003,763095.804579742 2949436.33850239,
763086.132105649 2949451.46730207,763078.452329651 2949462.11549407,
763075.354136904 2949466.17407812,763064.362142565 2949477.64291974,
763059.953961626 2949481.28983009,762994.637609571 2949532.04103014,
762990.568508415 2949535.06640477,762986.710889563 2949539.61421415,
763117.237897679 2949709.50493431,763235.236617789 2949617.95619822,
763287.718121842 2949562.20592617,763111.553321674 2949423.91664605,
763104.471273676 2949418.44119003)))', 2249));
st_perimeter
---------
845.227713366825
(1 row)
Examples: Geography
Return perimeter in meters and feet for Polygon and MultiPolygon. Note this is geography (WGS 84 long lat)
SELECT ST_Perimeter(geog) As per_meters, ST_Perimeter(geog)/0.3048 As per_ft
FROM ST_GeogFromText('POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.1776848522251 42.3902896512902))') As geog;
per_meters | per_ft
-----------------+------------------
37.3790462565251 | 122.634666195949
-- MultiPolygon example --
SELECT ST_Perimeter(geog) As per_meters, ST_Perimeter(geog,false) As per_sphere_meters, ST_Perimeter(geog)/0.3048 As per_ft
FROM ST_GeogFromText('MULTIPOLYGON(((-71.1044543107478 42.340674480411,-71.1044542869917 42.3406744369506,
-71.1044553562977 42.340673886454,-71.1044543107478 42.340674480411)),
((-71.1044543107478 42.340674480411,-71.1044860600303 42.3407237015564,-71.1045215770124 42.3407653385914,
-71.1045498002983 42.3407946553165,-71.1045611902745 42.3408058316308,-71.1046016507427 42.340837442371,
-71.104617893173 42.3408475056957,-71.1048586153981 42.3409875993595,-71.1048736143677 42.3409959528211,
-71.1048878050242 42.3410084812078,-71.1044020965803 42.3414730072048,
-71.1039672113619 42.3412202916693,-71.1037740497748 42.3410666421308,
-71.1044280218456 42.3406894151355,-71.1044543107478 42.340674480411)))') As geog;
per_meters | per_sphere_meters | per_ft
------------------+-------------------+------------------
257.634283683311 | 257.412311446337 | 845.256836231335
See Also
, ,
ST_Perimeter2D
Returns the 2-dimensional perimeter of the geometry, if it
is a polygon or multi-polygon. This is currently an alias for ST_Perimeter.
float ST_Perimeter2D
geometry geomA
Description
Returns the 2-dimensional perimeter of the geometry, if it
is a polygon or multi-polygon.
This is currently an alias for ST_Perimeter. In future versions ST_Perimeter may return the highest dimension perimeter for a geometry. This is still under consideration
See Also
ST_3DPerimeter
Returns the 3-dimensional perimeter of the geometry, if it
is a polygon or multi-polygon.
float ST_3DPerimeter
geometry geomA
Description
Returns the 3-dimensional perimeter of the geometry, if it
is a polygon or multi-polygon. If the geometry is 2-dimensional, then the 2-dimensional perimeter is returned.
&Z_support;
Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D
Examples
Perimeter of a slightly elevated polygon in the air in Massachusetts state plane feet
SELECT ST_3DPerimeter(the_geom), ST_Perimeter2d(the_geom), ST_Perimeter(the_geom) FROM
(SELECT ST_GeomFromEWKT('SRID=2249;POLYGON((743238 2967416 2,743238 2967450 1,
743265.625 2967416 1,743238 2967416 2))') As the_geom) As foo;
ST_3DPerimeter | st_perimeter2d | st_perimeter
------------------+------------------+------------------
105.465793597674 | 105.432997272188 | 105.432997272188
See Also
, ,
ST_PointOnSurface
Returns a POINT guaranteed to lie on the surface.
geometry ST_PointOnSurface
geometry
g1
Description
Returns a POINT guaranteed to intersect a surface.
&sfs_compliant; s3.2.14.2 // s3.2.18.2
&sqlmm_compliant; SQL-MM 3: 8.1.5, 9.5.6.
According to the specs, ST_PointOnSurface works for surface geometries (POLYGONs, MULTIPOLYGONS, CURVED POLYGONS). So PostGIS seems to be extending what
the spec allows here. Most databases Oracle,DB II, ESRI SDE seem to only support this function for surfaces. SQL Server 2008 like PostGIS supports for all common geometries.
&Z_support;
Examples
SELECT ST_AsText(ST_PointOnSurface('POINT(0 5)'::geometry));
st_astext
------------
POINT(0 5)
(1 row)
SELECT ST_AsText(ST_PointOnSurface('LINESTRING(0 5, 0 10)'::geometry));
st_astext
------------
POINT(0 5)
(1 row)
SELECT ST_AsText(ST_PointOnSurface('POLYGON((0 0, 0 5, 5 5, 5 0, 0 0))'::geometry));
st_astext
----------------
POINT(2.5 2.5)
(1 row)
SELECT ST_AsEWKT(ST_PointOnSurface(ST_GeomFromEWKT('LINESTRING(0 5 1, 0 0 1, 0 10 2)')));
st_asewkt
----------------
POINT(0 0 1)
(1 row)
See Also
,
ST_Project
Returns a POINT projected from a start point using a distance in meters and bearing (azimuth) in radians.
geography ST_Project
geography
g1
float
distance
float
azimuth
Description
Returns a POINT projected along a geodesic from a start point using an azimuth (bearing) measured in radians and distance measured in meters. This is also called a direct geodesic problem.
The azimuth is sometimes called the heading or the bearing in navigation. It is measured relative to true north (azimuth zero). East is azimuth 90 (π/2), south is azimuth 180 (π), west is azimuth 270 (3π/2).
The distance is given in meters.
Availability: 2.0.0
Example: Using degrees - projected point 100,000 meters and bearing 45 degrees
SELECT ST_AsText(ST_Project('POINT(0 0)'::geography, 100000, radians(45.0)));
st_astext
--------------------------------------------
POINT(0.635231029125537 0.639472334729198)
(1 row)
See Also
, , PostgreSQL Math Functions
ST_Relate
Returns true if this Geometry is spatially related to
anotherGeometry, by testing for intersections between the
Interior, Boundary and Exterior of the two geometries as specified
by the values in the intersectionMatrixPattern. If no intersectionMatrixPattern
is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries.
boolean ST_Relate
geometry geomA
geometry geomB
text intersectionMatrixPattern
text ST_Relate
geometry geomA
geometry geomB
text ST_Relate
geometry geomA
geometry geomB
integer BoundaryNodeRule
Description
Version 1: Takes geomA, geomB, intersectionMatrix and Returns 1 (TRUE) if this Geometry is spatially related to
anotherGeometry, by testing for intersections between the
Interior, Boundary and Exterior of the two geometries as specified
by the values in the DE-9IM matrix pattern.
This is especially useful for testing compound checks of intersection, crosses, etc in one step.
Do not call with a GeometryCollection as an argument
This is the "allowable" version that returns a
boolean, not an integer. This is defined in OGC spec
This DOES NOT automagically include an index call. The reason for that
is some relationships are anti e.g. Disjoint. If you are
using a relationship pattern that requires intersection, then include the &&
index call.
Version 2: Takes geomA and geomB and returns the
Version 3: same as version 2, but allows to specify a boundary node rule (1:OGC/MOD2, 2:Endpoint, 3:MultivalentEndpoint, 4:MonovalentEndpoint)
Do not call with a GeometryCollection as an argument
not in OGC spec, but implied. see s2.1.13.2
Performed by the GEOS module
&sfs_compliant; s2.1.1.2 // s2.1.13.3
&sqlmm_compliant; SQL-MM 3: 5.1.25
Enhanced: 2.0.0 - added support for specifying boundary node rule (requires GEOS >= 3.0).
Examples
--Find all compounds that intersect and not touch a poly (interior intersects)
SELECT l.* , b.name As poly_name
FROM polys As b
INNER JOIN compounds As l
ON (p.the_geom && b.the_geom
AND ST_Relate(l.the_geom, b.the_geom,'T********'));
SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2));
st_relate
-----------
0FFFFF212
SELECT ST_Relate(ST_GeometryFromText('LINESTRING(1 2, 3 4)'), ST_GeometryFromText('LINESTRING(5 6, 7 8)'));
st_relate
-----------
FF1FF0102
SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '0FFFFF212');
st_relate
-----------
t
SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '*FF*FF212');
st_relate
-----------
t
See Also
, , , ,
ST_RelateMatch
Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2
boolean ST_RelateMatch
text intersectionMatrix
text intersectionMatrixPattern
Description
Takes intersectionMatrix and intersectionMatrixPattern and Returns true if the intersectionMatrix satisfies
the intersectionMatrixPattern. For more information refer to .
Availability: 2.0.0 - requires GEOS >= 3.3.0.
Examples
SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
-- result --
t
--example of common intersection matrix patterns and example matrices
-- comparing relationships of involving one invalid geometry and ( a line and polygon that intersect at interior and boundary)
SELECT mat.name, pat.name, ST_RelateMatch(mat.val, pat.val) As satisfied
FROM
( VALUES ('Equality', 'T1FF1FFF1'),
('Overlaps', 'T*T***T**'),
('Within', 'T*F**F***'),
('Disjoint', 'FF*FF****') As pat(name,val)
CROSS JOIN
( VALUES ('Self intersections (invalid)', '111111111'),
('IE2_BI1_BB0_BE1_EI1_EE2', 'FF2101102'),
('IB1_IE1_BB0_BE0_EI2_EI1_EE2', 'F11F00212')
) As mat(name,val);
See Also
,
ST_ShortestLine
Returns the 2-dimensional shortest line between two geometries
geometry ST_ShortestLine
geometry
g1
geometry
g2
Description
Returns the 2-dimensional shortest line between two geometries. The function will
only return the first shortest line if more than one, that the function finds.
If g1 and g2 intersects in just one point the function will return a line with both start
and end in that intersection-point.
If g1 and g2 are intersecting with more than one point the function will return a line with start
and end in the same point but it can be any of the intersecting points.
The line returned will always start in g1 and end in g2.
The length of the line this function returns will always be the same as ST_Distance returns for g1 and g2.
Availability: 1.5.0
Examples
Shortest line between point and linestring
SELECT ST_AsText(
ST_ShortestLine('POINT(100 100)'::geometry,
'LINESTRING (20 80, 98 190, 110 180, 50 75 )'::geometry)
) As sline;
sline
-----------------
LINESTRING(100 100,73.0769230769231 115.384615384615)
shortest line between polygon and polygon
SELECT ST_AsText(
ST_ShortestLine(
ST_GeomFromText('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'),
ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
)
) As slinewkt;
LINESTRING(140.752120669087 125.695053378061,121.111404660392 153.370607753949)
See Also
, , ,
ST_Touches
Returns TRUE if the geometries have at least one point in common,
but their interiors do not intersect.
boolean ST_Touches
geometry
g1
geometry
g2
Description
Returns TRUE if the only points in common between
g1 and g2 lie in the union of the
boundaries of g1 and g2.
The ST_Touches relation applies
to all Area/Area, Line/Line, Line/Area, Point/Area and Point/Line pairs of relationships,
but not to the Point/Point pair.
In mathematical terms, this predicate is expressed as:
The allowable DE-9IM Intersection Matrices for the two geometries are:
FT*******
F**T*****
F***T****
Do not call with a GEOMETRYCOLLECTION as an argument
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid using an index, use _ST_Touches instead.
&sfs_compliant; s2.1.1.2 // s2.1.13.3
&sqlmm_compliant; SQL-MM 3: 5.1.28
Examples
The ST_Touches predicate returns TRUE in all the following illustrations.
POLYGON / POLYGON
POLYGON / POLYGON
POLYGON / LINESTRING
LINESTRING / LINESTRING
LINESTRING / LINESTRING
POLYGON / POINT
SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
st_touches
------------
f
(1 row)
SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
st_touches
------------
t
(1 row)
ST_Within
Returns true if the geometry A is completely inside geometry B
boolean ST_Within
geometry
A
geometry
B
Description
Returns TRUE if geometry A is completely inside geometry B. For this function to make
sense, the source geometries must both be of the same coordinate projection,
having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then
the two geometries are considered spatially equal.
Performed by the GEOS module
Do not call with a GEOMETRYCOLLECTION as an argument
Do not use this function with invalid geometries. You will get unexpected results.
This function call will automatically include a bounding box
comparison that will make use of any indexes that are available on
the geometries. To avoid index use, use the function
_ST_Within.
NOTE: this is the "allowable" version that returns a
boolean, not an integer.
&sfs_compliant; s2.1.1.2 // s2.1.13.3
- a.Relate(b, 'T*F**F***')
&sqlmm_compliant; SQL-MM 3: 5.1.30
Examples
--a circle within a circle
SELECT ST_Within(smallc,smallc) As smallinsmall,
ST_Within(smallc, bigc) As smallinbig,
ST_Within(bigc,smallc) As biginsmall,
ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
FROM
(
SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
--Result
smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
--------------+------------+------------+------------+------------+------------
t | t | f | t | t | t
(1 row)
See Also
, ,