The Fieldtree: A Data Structure for Geographic Information Systems

Efficient access methods, such as indices, are indispensable for the quick answer to database queries. In spatial databases the selection of an appropriate access method is particularly critical since different types of queries pose distinct requirements and no known data structure outperforms all others for all types of queries. Thus, spatial access methods must be designed for excelling in a particular kind of inquiry while performing reasonably in the other ones. This article describes the Fieldtree, a data structure that provides one of such access methods. The Fieldtree has been designed for GIS and similar applications, where range queries are predominant and spatial nesting and overlaping of objects are common. Besides their hierarchical organization of space, Fieldtrees are characterized by three other features:(i) they subdivide space regularly, (ii) spatial objects are never fragmented, and (iii) semantic information can be used to assign the location of a certain object in the tree. Besides describing the Fieldtree this work presents analytical results on several implementations of those variants, and compares them to published results on the Rtree and the R+tree.