- Axiom of choice (Wikipedia)
In mathematics, the axiom of choice, abbreviated AC or AoC, is an axiom of set theory equivalent to the statement that a Cartesian product of a collection of non-empty sets is non-empty. Informally put, the axiom of choice says that given any collection of sets, each containing at least one element, it is possible to construct a new set by choosing one element from each set, even if the collection is infinite.
- The Many Lives of Null Island (stamen.com)
At risk of ruining the secret for you, Null Island is a long-running inside joke among cartographers. It is an imaginary island located at a real place: the coordinates of 0º latitude and 0º longitude, a location in the Atlantic Ocean off the coast of Africa where the Prime Meridian meets the Equator, hundreds of miles from any real dry land.
- Null Island (Wikipedia)
Null Island is the location at zero degrees latitude and zero degrees longitude (0°N 0°E), i.e., where the prime meridian and the equator intersect. Since there is no landmass located at these coordinates, it is not an actual island. The name is often used in mapping software as a placeholder to help find and correct database entries that have erroneously been assigned the coordinates 0,0. Although “Null Island” started as a joke within the geospatial community, it has become a useful means of addressing a recurring issue in geographic information science.