Multiple zooming in geographic maps

摘要

We present a zooming model, based on a level-of-detail (LOD) approach, aimed at visualizing sequences of gradually simplified representations of a given geographic map. We first describe a set of basic zooming primitives as transitions between maps at different LOD. We then define a new multiple zooming primitive on top of the basic ones, and show theoretical results concerning this new primitive with practical implications. Finally, we put the proposed theoretical model into practice, and suggest an implementation of maps and zooming primitives in terms of PLA-structures, a topological invariant suitable for the inclusion in a visual interaction environment based on a focus + context approach.