1. A non-transitory computer storage medium storing instructions executable by a processor of a computer that when executed cause the computer to: receive two points of data selected from a corpus of spatial data; access a hierarchical index on the corpus of spatial data to choose candidate nodes, wherein the hierarchical 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 hierarchical index, where the candidate nodes comprise a proper subset of the nodes in the hierarchical index, such that the spatial relationship is not determined between the two points and non-candidate nodes; and based, at least in part, on the determined spatial relationships, select a candidate node for construction of a geometric figure describing the corpus of spatial data; wherein the instructions further comprise instructions that when executed by the processor cause the computer to choose candidate nodes by: at each level in the hierarchical index, starting with the root node entries as the candidate nodes and until a leaf node entry is selected: determining respective angles between a line segment having the two points as endpoints and respective candidate nodes in the level; selecting a candidate node as a path node, based at least in part, on the determined angles; choosing child nodes of the path node in a next level as candidate nodes, such that child nodes of the candidate nodes not selected as the path node are not chosen as candidate nodes in the next level; and when a leaf node entry is selected as a path node, selecting the leaf node entry for the construction of the geometric figure.