Nearest base-neighbor search on spatial datasets

This paper presents a nearest base-neighbor (NBN) search that can be applied to a clustered nearest neighbor problem on spatial datasets with static properties. Given two sets of data points R and S, a query point q, distance threshold δ and cardinality threshold k, the NBN query retrieves a nearest point r (called the base-point) in R where more than k points in S are located within the distance δ. In this paper, we formally define a base-point and NBN problem. As the brute-force approach to this problem in massive datasets has large computational and I/O costs, we propose in-memory and external memory processing techniques for NBN queries. In particular, our proposed in-memory algorithms are used to minimize I/Os in the external memory algorithms. Furthermore, we devise a solution-based index, which we call the neighborhood-augmented grid, to dramatically reduce the search space. A performance study is conducted both on synthetic and real datasets. Our experimental results show the efficiency of our proposed approach.