Directory of Map Projections

What is a projection?

Previous | Next

rectangular polyconic

War Office

Parameters: Latitude of origin, Standard parallel




Meridians: Central meridian is a straight line. All other meridians are complex curves, equally spaced along the equator or along two chosen parallels symmetrical about the equator. Meridians intersect all parallels at right angles.
Parallels: Equator is a straight line, poles are points, and all other parallels are nonconcentric circular arcs spaced at true distances along the central meridian. Each parallel has a curvature identical to its curvature on a cone tangent at that latitude. Many cones are involved; hence, the name “Polyconic projection.”.
Symmetry: About the central meridian or the equator.


True along the central meridian and along the equator or two chosen parallels of true scale.


Free of distortion only along the central meridian. Although meridians intersect parallels at right angles, there is some angular distortion at all points other than along the central meridian.


Large-scale military mapping in Great Britain.

Similar projections

Listed under Polyconic projection.

Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.