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
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. Requires Proj >= 4.9.0 to take advantage of the new feature.
Changed: 3.0.0 - does not depend on SFCGAL anymore.
This method implements the OpenGIS 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.
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.
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;