The ANN-tree: an index for efficient approximate nearest neighbor search

We explore the problem of approximate nearest neighbor searches. We propose an index structure, the ANN-tree (approximate nearest neighbor tree) to solve this problem. The ANN-tree supports high accuracy nearest neighbor search. The actual nearest neighbor of a query point can usually be found in the first leaf page accessed. The accuracy increases to near 100% if a second page is accessed. This is not achievable via traditional indexes. Even if an exact nearest neighbor query is desired, the ANN-tree is demonstrably more efficient than existing structures like the R*-tree. This makes the ANN-tree a preferable index structure for both exact and approximate nearest neighbor searches. We present the index in detail and provide experimental results on both real and synthetic data sets.