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PostGIS 1.5.8 Manual200 / 310See AlsoST_Contains, ST_Crosses, ST_Dimension, ST_Intersects7.8.31 ST_PerimeterST_Perimeter — Return the length measurement of the boundary of an ST_Surface or ST_MultiSurface value. (Polygon, Multipolygon)Synopsisfloat ST_Perimeter(geometry g1);DescriptionReturns the 2D perimeter of the geometry if it is a ST_Surface, ST_MultiSurface (Polygon, Multipolygon). 0 is returned fornon-areal geometries. For linestrings use ST_Length. Measurements are in the units of the spatial reference system of thegeometry.Currently this is an alias for ST_Perimeter2D, but this may change to support higher dimensions.This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.5.1This method implements the SQL/MM specification. SQL-MM 3: 8.1.3, 9.5.4ExamplesReturn perimeter in feet for polygon and multipolygon. Note this is in feet because 2249 is Mass State Plane FeetSELECT 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)See AlsoST_Length