1. A non-transitory computer storage medium storing instructions configured to cause a computer to: receive two points selected from a corpus of spatial data; access a hierarchical index on the corpus of spatial data to choose candidate nodes, where the index comprises a hierarchical arrangement of one or more nodes arranged in paths from root node entries to leaf node entries; determine a spatial relationship between the two points and the candidate nodes in the index, where the candidate nodes comprise a proper subset of the nodes in the index, such that the spatial relationship is not determined between the two points and some non-candidate nodes; and based, at least in part, on the determined spatial relationships, select a candidate node for processing related to construction of a geometric figure describing the corpus of spatial data.