[decafb]

For reference: The generic name what op does is "spatial indexing". There is an algorithm for efficiently working with such data called Hilbert R-tree (https://en.wikipedia.org/wiki/Hilbert_R-tree). But there are alternatives (see https://en.wikipedia.org/wiki/Spatial_database).

Many databases nowadays contain functions to these operations (e.g. https://dev.mysql.com/doc/refman/5.7/en/spatial-analysis-fun...)

[brians]

They can even be explained to a surprisingly low tech operator, with pre-calculation at a high tech level: http://www2.isye.gatech.edu/~jjb/research/mow/mow.pdf