GeoHash Algorithm first described by Gustavo Niemeyer in February 2008. By interleaving latitude and longitude information in a bitwise fashion, a composite value is generated that provides a high resolution geographic point, and is well suited for storage or transmission as a character string.
Geohash MCP.
RTree for leveldb
A data compression library for large sized Geopolygons.
hexagon geohashing (depends on geocomb-cpp)