Plane Table

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. II. For some work, a compass needle in a box. The box has a square or rectangular base with the edges beveled like a rule and parallel and perpendicular to the zero line of the compass ring. The compass needle is sometimes mounted on the rule of the alidade but the separate compass is better.