{Polyconic projection} (Map Making), a projection of the
earth's surface, or any portion thereof, by which each
narrow zone is projected upon a conical surface that
touches the sphere along this zone, the conical surface
being then unrolled. This projection differs from conic
projection in that latter assumes but one cone for the
whole map. Polyconic projection is that in use in the
United States coast and geodetic survey.