|Hemispheres in first Stabius-Werner projection|
The shape of maps is not constrained to rectangles, discs or ellipses. Some are not even convex, like those created by the beautiful projections devised (ca. 1500) by Johann Stabius of Vienna, also known as Stab. His three cordiform ("heart-shaped") projections were so popularized in treatises by Johannes Werner that they usually bear the latter's name. They all share some features in the normal aspect:
|Stabius-Werner's third projection including the whole world but the very Eastern end of Siberia|
Only parallel scaling distinguishes the three projections. On a worldwide map drawn using the first one, the Equator is a circle and boundary meridians would significantly overlap, therefore the map is normally clipped to one hemisphere. On the third one, the equatorial scale is slightly larger than the central meridian's, so there is a small overlap north of the 60° parallel.
|Werner (second Stabius) map, polar aspect|
The three Stabius-Werner projections are equal-area and clearly suggest the Earth's roundness, much like as its crust were cut at a meridian and peeled off. However, only the second version — known as the Werner projection — was widely used. It has the Equator twice as long as the central meridian, therefore all parallels are standard lines and there is no overlap.
Works by Oronce Finé (1531) and Mercator (1538) employed a butterfly-shaped Werner map interrupted at the Equator, with a central meridian emphasizing the Eastern hemisphere.
|The Schjerning V projection|
This projection is seldom seen today in its original shape, but it has been used in some specialized forms, notably in Wilhelm Schjerning's sixth projection (interrupted in irregular petals around Antarctica as an inverted star-like map emphasizing oceans), Goode's polar equal-area (similar, north polar privileging land masses, multiple central meridians) and combined with part of an azimuthal hemisphere for a more conventional star, with rescaled parallels in the "tetrahedral" and William-Olsson's projections.
In the same 1904 paper, Schjerning proposed five other projections — one equidistant conic, two modified azimuthals, and two variations of the second Stabius-Werner: Schjerning IV, an oblique aspect, and Schjerning V, a normal aspect with parallels shortened by 50%. After a proportional rescaling, the fifth design regains Werner's original area, but not the distortion-free central meridian.
|A butterfly-shaped Werner map, interrupted at the Equator.||Transverse Werner map, interrupted at 25°E|
|Bonne map, central parallel 45°N|
In a Bonne map, except in one special case mentioned below all parallels are concentric arcs of circle, all equally spaced and all standard lines. Scale is also correct along the straight vertical central meridian. For construction, one parallel at the sphere is chosen, and a cone tangent at that central parallel is built. That parallel's radius at the map is the same as the radius along the cone. All other parallels's radii are marked accordingly.
|Bonne map, central parallel 15°S|
As a consequence, each central parallel creates a different Bonne map. Two special cases are well-known: