ST_Area calculates the area of a polygonal geometry. The result uses the units defined by the geometry’s spatial reference system (SRID), so a geometry stored with SRID 3857 produces square-meter values. section 10.3.3 section 10.5.2
Measure a theme park
Calculate Walt Disney World’s area in square kilometers and acres: SELECT name, tourism, ST_Area(way) / 1000000.0 AS area_sq_km, ST_Area(way) / 4046.86 AS area_acres FROM florida.planet_osm_polygon WHERE name = 'Walt Disney World'; The query returns approximately 96.08 square kilometers and 23,741.93 acres. section 10.5.2
Use ST_Area to:
- Compare polygon sizes by ordering geometries with ORDER BY ST_Area(way). section 10.3.3
- Convert raw SRID-based results into more practical units by dividing the returned value. section 10.5.2
Listing 10.17 Calculating the area of Walt Disney World
SELECT name, tourism, ST_Area(way) / 1000000.0 AS area_sq_km, ST_Area(way) / 4046.86 AS area_acres FROM florida.planet_osm_polygon WHERE name = 'Walt Disney World';
Runnable SQL for calculating a polygon’s area in square kilometers and acres. section 10.5.2
