RTree
This package implements an R-Tree data structure.
It follows the approach outlined in R-Trees - A Dynamic Index Structure For Spatial Searching.
The implementation is in-memory only, and is designed in such a way that the internal representation of the R-Tree is exposed. In particular, this allows the R-Tree to be serialised for storage or transmission. Note that this package doesn't provide any serialisation - that is an exercise left up to the package user.