Hammer retroazimuthal projection
![](https://cdn.statically.io/img/upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Hammer_retroazimuthal_projection_combined1.jpg/300px-Hammer_retroazimuthal_projection_combined1.jpg)
![](https://cdn.statically.io/img/upload.wikimedia.org/wikipedia/commons/thumb/2/23/Hammer_Retroazimuthal_with_Tissot%27s_Indicatrices_of_Distortion.svg/300px-Hammer_Retroazimuthal_with_Tissot%27s_Indicatrices_of_Distortion.svg.png)
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.[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.
See also[edit]
References[edit]
- ^ Snyder, John P. (1993). Flattening the Earth: Two Thousand Years of Map Projections. Chicago: University of Chicago Press. pp. 228–229. ISBN 0-226-76747-7. Retrieved 2011-11-14.