polyconstd

Polyconic Projection — Standard

Classification

Polyconic

Identifier

polyconstd

Graticule

Central Meridian: A straight line.

Meridians: Complex curves spaced equally along the Equator and each parallel, and concave toward the central meridian.

Parallels: The Equator is a straight line. All other parallels are nonconcentric circular arcs spaced at true distances along the central meridian.

Poles: Normally circular arcs, enclosing the same angle as the displayed parallels.

Symmetry: About the Equator or the central meridian.

Features

polyconstd implements the Polyconic projection directly on a reference ellipsoid, consistent with the industry-standard definition of this projection. See polycon for an alternative implementation based on rotating the rectifying sphere.

For this projection, each parallel has a curvature identical to its curvature on a cone tangent at that latitude. Since each parallel has its own cone, this is a “polyconic” projection. Scale is true along the central meridian and along each parallel. This projection is free of distortion only along the central meridian; distortion can be severe at extreme longitudes. This projection is neither conformal nor equal-area.

Parallels

By definition, this projection has no standard parallels, since every parallel is a standard parallel.

Remarks

• This projection was apparently originated about 1820 by Ferdinand Rudolph Hassler. It is also known as the American Polyconic and the Ordinary Polyconic projection.

• Mapping Toolbox™ uses a different implementation of the standard polyconic projection for displaying coordinates on axesm-based maps than for projecting coordinates using the projfwd or projinv function. These implementations may produce differing results.

Limitations

Longitude data greater than 75º east or west of the central meridian is trimmed.

Example

landareas = shaperead('landareas.shp','UseGeoCoords',true);
axesm ('polyconstd', 'Frame', 'on', 'Grid', 'on');
geoshow(landareas,'FaceColor',[1 1 .5],'EdgeColor',[.6 .6 .6]);
tissot;