ST_3DPerimeter
Name
ST_3DPerimeter — Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon.
Synopsis
    
     float
     
      ST_3DPerimeter
     
     (
    
    geometry
    
     geomA
    
    
     )
    
    ;
   
Description
Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. If the geometry is 2-dimensional, then the 2-dimensional perimeter is returned.
   
    
   
   This function supports 3d and will not drop the z-index.
  
Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D
Examples
Perimeter of a slightly elevated polygon in the air in Massachusetts state plane feet
SELECT ST_3DPerimeter(the_geom), ST_Perimeter2d(the_geom), ST_Perimeter(the_geom) FROM
			(SELECT ST_GeomFromEWKT('SRID=2249;POLYGON((743238 2967416 2,743238 2967450 1,
743265.625 2967416 1,743238 2967416 2))') As the_geom) As foo;
  ST_3DPerimeter  |  st_perimeter2d  |   st_perimeter
------------------+------------------+------------------
 105.465793597674 | 105.432997272188 | 105.432997272188