PostGIS
Synopsis
float +`*`+ST_Area*(`geometry `g1`)`;
float +`*`+ST_Area*(`geography `geog, boolean
use_spheroid=true`)`;
Description
Returns the area of a polygonal geometry. For geometry types a 2D
Cartesian (planar) area is computed, with units specified by the SRID.
For geography types by default area is determined on a spheroid with
units in square meters. To compute the area using the faster but less
accurate spherical model 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. Requires PROJ >= 4.9.0 to take advantage of the new feature.
Changed: 3.0.0 - does not depend on SFCGAL anymore.
[.inlinemediaobject]
This
method implements the OGC
Simple Features Implementation Specification for SQL 1.1.
This method
implements the SQL/MM specification. SQL-MM 3: 8.1.2, 9.5.3
This function
supports Polyhedral surfaces.
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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(geom) sqft,
ST_Area(geom) * 0.3048 ^ 2 sqm
from (
select 'SRID=2249;POLYGON((743238 2967416,743238 2967450,
743265 2967450,743265.625 2967416,743238 2967416))' :: geometry geom
) subquery;
┌─────────┬─────────────┐
│ 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(geom) sqft,
ST_Area(ST_Transform(geom, 26986)) As sqm
from (
select
'SRID=2249;POLYGON((743238 2967416,743238 2967450,
743265 2967450,743265.625 2967416,743238 2967416))' :: geometry geom
) subquery;
┌─────────┬─────────────────┐
│ sqft │ sqm │
├─────────┼─────────────────┤
│ 928.625 │ 86.272430607008 │
└─────────┴─────────────────┘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(geog) / 0.3048 ^ 2 sqft_spheroid,
ST_Area(geog, false) / 0.3048 ^ 2 sqft_sphere,
ST_Area(geog) sqm_spheroid
from (
select ST_Transform(
'SRID=2249;POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))'::geometry,
4326
) :: geography geog
) as subquery;
┌──────────────────┬──────────────────┬──────────────────┐
│ sqft_spheroid │ sqft_sphere │ sqm_spheroid │
├──────────────────┼──────────────────┼──────────────────┤
│ 928.684405784452 │ 927.049336105925 │ 86.2776044979692 │
└──────────────────┴──────────────────┴──────────────────┘If your data is in geography already:
select ST_Area(geog) / 0.3048 ^ 2 sqft,
ST_Area(the_geog) sqm
from somegeogtable;