Continuous Generalization for Visualization on Small Mobile Devices

Abstract

With the increasing availability of small mobile computers, there is also an increasing demand for visualizing cartographic objects on those devices. Prominent applications are location based services in general, and car and pedestrian navigation in particular. In order to be able to offer both detail and overview of a spatial situation, the devices have to provide flexible zooming in and out in real-time. The presentation of spatial data sets in different zoom levels or resolutions is usually achieved using generalization operations. When larger scale steps have to be overcome, the shape of individual objects typically changes dramatically, also objects may disappear or merge with others to form new objects. As theses steps typically are discrete in nature, this leads to “popping effects” when going from one level of detail to the other. In this paper, we will describe an approach to decompose generalization methods into elementary operations that can then be implemented in a continuous way. For example in the case of displacement, an object will not simply jump from one position to the other, but slowly shifted from its original position to the new one. In the case of simplification of building ground plans, the elementary operations e.g. care for removing extrusions or intrusions of buildings, as well as offsets. In the paper we will identify elementary generalization operations and also present their implementation as a continuous operations. We will apply these concepts for line generalization, the generalization of building ground plans and for displacement.