Returns the geometry of the smallest box in which the geometry passed as parameter fits. Normally it is a rectangle, but for a point the same point is obtained and for an horizontal or vertical line is obtained the line defined by its opposite points.

1 geo.getEnvelope

    <geom_column /> *
               <coords>0 0,0 1,1 1,1 0,0 0</coords>
    <from table='roads'  alias='a'  />