The Wiechel projection is an pseudoazimuthal, equal-area map projection, and a novelty map presented by William H. Wiechel in 1879. When centered on the pole, it has semicircular meridians arranged in a pinwheel. Distortion of direction, shape, and distance is considerable in the edges.

In polar aspect, the Wiechel projection can be expressed as so:

The Wiechel can be obtained via an area-preserving polar transformation of the Lambert azimuthal equal-area projection. In polar representation, the required transformation is of the form

where ${\displaystyle (r_{L},\theta _{L})}$ and ${\displaystyle (r_{W},\theta _{W})}$ are the polar coordinates of the Lambert and Wiechel maps, respectively. The determinant of the Jacobian of the transformation is equal to unity, ensuring that it is area-preserving. The Wiechel map thus serves as a simple example that equal-area projections of the sphere onto the disk are not unique, unlike conformal maps which follow the Riemann mapping theorem.