Generalization, On-the-Fly

Abstract

Map generalization defines the process of producing maps at coarser levels of detail (LOD), while retaining essential characteristics of the underlying geographic information. On-the-fly generalization, then, denotes the use of auto- mated generalization techniques in real time. According to [1], this process creates a temporary, generalized dataset exclusively for visualization, not for storage or other pur- poses. On-the-fly generalization is intimately linked to highly interactive applications of cartography such as web mapping, mobile mapping [e. g., in location-based services (LBS)], and real-time decision support systems (e. g., in disaster and evacuation management) that involve multi- ple spatial scales. As it takes place in a highly interactive setting, the cartographic quality requirements are typically relaxed compared to traditional, high-quality paper maps. On the other hand, (near) real-time behavior is impera- tive. Solutions that satisfy the above requirements can general- ly be assigned to two groups. The first group of approach- es relies on fast map generalization algorithms that gener- ate coarser levels of detail in real time. The second group utilizes hierarchical spatial data structures. In both cas- es, the generalization operations that are implemented are generally rather simple from a functional point of view, compared to the cartographically more sophisticated, yet computationally more costly algorithms that are typically used in the production of high-quality paper maps. Close- ly related to on-the-fly map generalization is progressive vector data transmission (i. e., the transmission, over a net- work, of vector datasets at progressively finer detail). G 24. Sheppard, E., McMaster, R.B.: Scale and Geographic Inquiry: Nature Society and Method. Blackwell Publishing, Malden, MA (2004) 25. Weibel, R., Dutton, G.: Generalizing Spatial Data and Dealing with Multiple Representations. In: Longley, P., Goodchild, M.F., Maguire, D.J., Rhind, D.W. (eds.) Geographical Information Sys- tems, pp. 125–156. JohnWiley, New York (1999)