rpav/spatial-trees — pull request #2 by guicho271828 (2013-11-24 05:35:42+00:00)
Title: Nearest neighbor search

added nearest neighbour search function along with enough testing.

reference:

Nearest Neighbor Queries
N Roussopoulos, S Kelley, F Vincent - ACM sigmod record, 1995

http://scholar.google.co.jp/scholar?hl=ja&q=+Nearest+Neighbor+Queries&btnG=&lr=