Hammer retroazimuthal projection

The Hammer retroazimuthal projection is a modified azimuthal proposed by Ernst Hermann Heinrich Hammer in 1910.

[1] Additionally, all distances from the center of the map are proportional to what they are on the globe.

In whole-world presentation, the back and front hemispheres overlap, making the projection a non-injective function.

The back hemisphere can be rotated 180° to avoid overlap, but in this case, any azimuths measured from the back hemisphere must be corrected.

Given a radius R for the projecting globe, the projection is defined as: where and The latitude and longitude of the point to be plotted are φ and λ respectively, and the center point to which all azimuths are to be correct is given as φ1 and λ0.

The full Hammer retroazimuthal projection, 15° graticule, centered on the north pole.
The full Hammer retroazimuthal projection centered on Mecca , with Tissot's indicatrix of deformation. Back hemisphere has been rotated 180° to avoid overlap.