2002/01/01 by Waldo Tobler · 1 citation
Social Sciences · Physics and Astronomy · Arts and Humanities · Mathematics · Engineering · #Historical Geography and Cartography #Historical Astronomy and Related Studies #Historical Studies on Spain #Azimuth #Equator #Bent molecular geometry #Parallels #Projection (relational algebra) #Map projection #Stereographic projection #Geography #Geometry #Cartography #Geology #Mathematics #Geodesy #Latitude #Algorithm #Engineering
paper · doi:10.1559/152304002782064574
openalex publication_date 2002/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
The qibla problem—determination of the direction to Mecca—has given rise to retro-azimuthal map projections, an interesting, albeit unusual and little known, class of map projections. Principal contributors to this subject were Craig and Hammer, both writing in 1910. A property of retro-azimuthal projections is that the parallels are bent downwards towards the equator. The resulting maps, when extended to the entire world, thus must overlap themselves. An unusual recent discovery from Iran suggests that Muslims might have been prior inventors of a similar projection, by at least several centuries. A later corollary by Schoy leads to a new "cylindrical" azimuthal map projection with parallels bending away from the equator, here illustrated for the first time.