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PostGIS 1.5.8 Manual193 / 3107.8.25 ST_Length_SpheroidST_Length_Spheroid — Calculates the 2D or 3D length of a linestring/multilinestring on an ellipsoid. This is useful if thecoordinates of the geometry are in longitude/latitude and a length is desired without reprojection.Synopsisfloat ST_Length_Spheroid(geometry a_linestring, spheroid a_spheroid);DescriptionCalculates the length of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude anda length is desired without reprojection. The ellipsoid is a separate database type and can be constructed as follows:SPHEROID[,,]SPHEROID["GRS_1980",6378137,298.257222101]NoteWill return 0 for anything that is not a MULTILINESTRING or LINESTRINGThis function supports 3d and will not drop the z-index.ExamplesSELECT ST_Length_Spheroid( geometry_column,’SPHEROID["GRS_1980",6378137,298.257222101]’ )FROM geometry_table;SELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2FROM (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--3DSELECT ST_Length_Spheroid( the_geom, sph_m ) As tot_len,ST_Length_Spheroid(ST_GeometryN(the_geom,1), sph_m) As len_line1,ST_Length_Spheroid(ST_GeometryN(the_geom,2), sph_m) As len_line2FROM (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