Vario-scale geo-information

Today, current practice is to store digital geographic data sets at multiple scales with mul-tiple representations, i.e. data is stored multiple times at a fixed number of resolution (or scale) intervals in so-called MRDB’s. In these data structures links between correspond-ing objects of the different resolution levels are stored, to offer consistency during the use of the data. Drawbacks of those structures are that redundant data is stored and that these structures are not suitable for progressive data transfer, because each resolution level requires its own graphic representation to be transferred. Raster images can accomodate progressive transfer nicely with techniques like wavelet compression and data pyramids. Due to the data structures, first a coarse representation can be send and later on refined with more details. It’s more difficult to obtain those effects with vector data, as these require more advanced data structures. In earlier research both the theoretical and practical (implementation) aspects of an ex-ample of such a more advanced data structure, the tGAP structure (topological Generalized Area Partitioning) have been described [Van Oosterom, 2005], [Van Oosterom et al., 2006]. Purpose of this tGAP structure is to store the data only once, with no redundancy of the geometry, and derive different representations of this same data on the fly according to the level of detail needed. In this research extensions to the original tGAP vario-scale data structures are to be found, to get to a continuous representation of the real world with respect to resolution, instead of a discretised representation in multiple layers, each only representing one res-olution level. This includes storage methods, semantics, progressive transfer of data over networks and smooth zoom and pan (e.g. geo-morphing) at the client side. Benefits of such an approach, but not limited to those mentioned here, are: • data consistency between different resolutions • possibility of progressive transfer • smooth zooming / panning