Cardinal Directions between Extended Spatial Objects
Roop Goyal and
Max Egenhofer IEEE Transactions on Knowledge and Data Engineering (in press).
Abstract
Cardinal directions complement topological relations and
approximate relations as qualitative spatial relations. They are
frequently used as selection criteria in spatial queries or for
assessing similarities of spatial scenes. Current models for
cardinal directions use quite crude approximations in the form of
the objectsÕ minimum bounding rectangles or their
generalizations to points. To overcome the limitations of these
models so that cognitively more plausible inferences can be made,
the direction-relation matrix is introduced. It partitions space
around a reference object and records into which direction tiles an
extended target object falls. At a finer level of granularity it
offers the option to capture how much of the target falls into each
direction tile. Further details due to the particular shape of the
target object may be captured for tiles that contain multiple
separations of the target. This multi-resolution representation
provides a better approximation for direction relations of
complexly structured spatial objects, including such shapes as
concave regions or objects with holes, and leads to a multi-level
model for processing spatial queries with direction relations.
Full article
Roop Goyal and
Max Egenhofer