Mastering Map Scale: Formalizing Guidelines for Multi-Scale Map Design Cynthia A. Brewer, Pennsylvania State University, cbrewer@psu.edu Barbara P. Buttenfield, University of Colorado – Boulder, babs@colorado.edu Abstract This paper extends European research on balancing the cartographic production workload. We emphasize the role of changes to the map display (such as symbol design or modification) in contrast to existing workload discussions that focus on changes to feature geometry. We report results demonstrating how symbol change combined with selection and elimination of subsets of features can produce maps through almost the entire range of scales. We demonstrate a method of establishing specific map display scales at which symbol modification should be imposed. We present a prototype decision tool called ScaleMaster that can be constructed for multi-scale map design across a small or large range of data resolutions, display scales, and map purposes. 1. Introduction Mapmaking at scales between those that correspond to available database resolutions can involve changes to the display (such as symbol changes), changes to feature geometry (data generalization), or both. Cartographic managers are thus faced with a variety of decisions, including: • Which compiled-data resolution will be used for maps at any given display scale; • At what point(s) in a multi-scale progression will map symbols be changed; • At what point(s) in a multi-scale progression must new data compilations be introduced; and • What are the most efficient ways to set up and manage cartographic workloads. From a processing standpoint, symbol modification is often less intensive than modifying data geometry, and thus changing symbol designs can reduce overall workloads for multi-resolution data modeling. The European community has emphasized the need to develop efficient workloads for scale changing and for generalization operations (for example, Cecconi et al. 2002; Bobzien et al. 2005) since many are computationally intensive or require tedious manual refinement. We extend the European research by emphasizing that changes to symbol design are often incorporated without other data generalization, especially when the target mapping scales show levels of detail that are similar to the resolution of compiled data. We demonstrate a method of establishing specific display scales at which symbol modification should be imposed. We prototype a decision tool called ScaleMaster for multi-scale map design across a small or large range of data resolution, display scales, and map purposes. 2. Background and Related Literature The process of modifying details in spatial data has been a subject of longstanding interest in many disciplines, judging by publications in Cartography, GIScience and Computer Science literature. The guiding principles underlying this body of work are to reduce visual clutter while preserving logical consistency. Data reduction through generalization can effect varying and sometimes dramatic changes in line length, local coordinate density, topology, and other 1