I am running the code found here http://www.boost.org/doc/libs/1_54_0_beta1/libs/geometry/doc/html/geometry/s... (not the intersect query, only the nn). The output is this: " knn query point: POINT(0 0) knn query result: POLYGON((4 4,4 4.5,4.5 4.5,4.5 4,4 4)) - 4 POLYGON((3 3,3 3.5,3.5 3.5,3.5 3,3 3)) - 3 POLYGON((2 2,2 2.5,2.5 2.5,2.5 2,2 2)) - 2 POLYGON((0 0,0 0.5,0.5 0.5,0.5 0,0 0)) - 0 POLYGON((1 1,1 1.5,1.5 1.5,1.5 1,1 1)) - 1 " What are the integers on the right? Indices of the polygons? Actually is not really clear to me what are we inserting in the tree..I tried finding some documentation on these methods, but I only found info on how to call them... What I want, is simply inserting some points in the tree and then search for nn of a query point. Thanks in advance, George