Section 2(75) in Assam Notified Urban Areas (Other than Guwahati) Building Rules, 2014
(75)"light plane" means the plane lying between the line of intersection of the floor of any room in a building with the outer surface or an exterior wall of the building and the straight lines drawn upwards and outwards from those lines drawn upward and outwards from lines perpendicular thereto an at angle of 63 ½ degrees to the horizontal;
