|Picture of the day|
The Hammer retroazimuthal projection is a modified azimuthal proposed by Ernst Hermann Heinrich Hammer in 1910. As a retroazimuthal projection, azimuths (directions) are correct from any point to the designated center point. In whole-world presentation, the back and front hemispheres overlap, making the projection a surjective function. Here, the frontside and backside hemispheres, both with a 15° graticule and center point of 45°N, 90°W, are presented side-by-side.