CaGIS Vol. 30, No. 1

ColorBrewer in Print: A Catalog of Color Schemes for Maps

Cynthia A. Brewer, Geoffrey W. Hatchard, and Mark A. Harrower

ColorBrewer is a tool that assists mapmakers in choosing and creating color schemes. It is available online at www.ColorBrewer.org. The color schemes range from 3 to 12 classes and are organized into three basic categories: sequential, diverging, and qualitative. Each of these scheme types has general perceptual characteristics which are described using Munsell hue, value, and chroma specifications. Each scheme has been proofed from color-separated negatives and adjusted to offer CMYK (cyan, magenta, yellow, and black) specifications that produce a readable map when they are used in process-printed publications. This paper offers a printed catalog of all of the ColorBrewer schemes to allow mapmakers to evaluate the appearance of each scheme before they commit to using them in print publications. Since process-color proofing is expensive, this catalog will reduce mapmakers’ costs and allow them to be more confident that their maps will make the transition from the desktop computing environment to publication without compromising the intended message through poor color specification.

Keywords: Symbolization, color, design, thematic mapping, printing

B-spline Functions and Wavelets for Cartographic Line Generalization

Eric Saux

Most line processing algorithms developed so far in cartographic generalization focus on polygonal curves (or polylines). This representation model is sometimes not sufficient for certain processes due to its lack of continuity or smoothness. Indeed, it may provide poor results for lines having “smooth” initial shapes such as roads. Thus, we suggest using a modeling method based on B-spline curves. A maritime case study described in this paper shows that this representation provides good results at a fixed scale and is suitable for several automatic line cartographic generalization operators (smoothing, displacement, aggregation and compression). Lastly, we discuss the application of B-spline wavelets used in dealing with multi-scaling.

Keywords: B-splines, line generalization, B-spline wavelets

Representation of Generalized Map Series Using Semi-Structured Data Models

Emmanuel Stefanakis

Large cartographic organizations worldwide produce generalized map series (GMS) in order to meet various user requirements. A GMS consists of maps of the same geographic region at different scales. Most of these maps currently are designed in a digital environment, and recently some of them have been distributed through the web. One important issue is the appropriate modeling and handling of cartographic entities composing individual maps in a GMS. Since these entities have rather complex descriptions and may be provided by various agencies, they usually do not conform to a fixed schema (i.e., they do not have a common structure). Hence, their representation in traditional data models, such as the relational or object-oriented, is not always feasible. This paper investigates the use of semi-structured data (SSD) models—an innovative approach recently developed in Information Technology for representing and handling entities in a GMS. Specifically, the Object Exchange Model (OEM), a popular database model for SSD, has been adopted to represent a GMS. How useful information can be extracted from such a representation using the LOREL query language—a popular language for SSD— is also shown.

Keywords: Map generalization, generalized map series (GMS), semi-structured data (SSD), Object Exchange Model (OEM), Lightweight Object REpository (LORE) system, LORE query Language (LOREL).

Projecting Global Datasets to Achieve Equal Areas

1. Lynn Usery, Michael P. Finn, John D. Cox, Thomas Beard, Sheila Ruhl, and Morgan Bearden

Scientists routinely accomplish global modeling in the raster domain, but recent research has indicated that the transformation of large areas through map projection equations leads to errors. This research attempts to gauge the extent of map projection and resampling effects on the tabulation of categorical areas by comparing the results of three datasets for seven common projections. The datasets, Global Land Cover, Holdridge Life Zones, and Global Vegetation, were compiled at resolutions of 30 arc-second, ½ degree, and 1 degree, respectively. These datasets were projected globally from spherical coordinates to plane representations. Results indicate significant problems in the implementation of global projection transformations in commercial software, as well as differences in areal accuracy across projections. The level of raster resolution directly affects the accuracy of areal tabulations, with higher resolution yielding higher accuracy. If the raster resolution is high enough for individual pixels to approximate points, the areal error tends to zero. The 30-arc-second cells appear to approximate this condition.

Commentary on “A History of Twentieth-Century American Academic Cartography” by Robert McMaster and Susanna McMaster

Sara Irina Fabrikant

In their contribution to the recent special issue of Cartography and Geographic Information Science on “Exploratory Essays: History of Cartography in the Twentieth Century” (Vol. 29, No. 3, pp. 305-321), McMaster and McMaster make the claim that “although the main development of thematic mapping can be traced to nineteenth-century Europe, it is in the twentieth-century United States that thematic cartography evolved as an academic discipline” (p. 306). In this commentary, I will argue and provide evidence for the idea that fundamental contributions to the development of academic thematic cartography were made in Europe, and that these developments occurred earlier than those implied by McMaster and McMaster in the U.S. In other words, I intend to show that the McMasters’ conclusion is a serious overstatement, possibly a blatant misstatement. Unfortunately this is not the first time such an inaccurate statement has been made in a U.S. publication; such statements are sometimes regrettably recited as received wisdom by others. Appearing as it does in a special issue on the history of 20th century cartography, the claim by McMaster and McMaster deserves to be elaborated further and supported by evidence, as it is an important yet doubtful assertion.

Keywords: History of cartography; thematic cartography, 20th century cartography, Germany, Austria, Switzerland

Response

Robert B. McMaster and Susann a McMaster

We appreciate the willingness of Sara Fabrikant to thoroughly review our recent paper on the “History of U.S. Academic Cartography,” and her thoughtful commentary. We are somewhat surprised that such a statement, while obviously being subjective in nature and rather tangential to the paper’s main point, could evoke such a response. Whether or not one is convinced by her argument depends on two issues—the validity of the scale of the analysis, and the meaning of the term “discipline,” as we use it in our paper. In our response, we will demonstrate how these two issues are key to making comparisons to our study meaningful. First of all, it is a pity that the History of Cartography editor of this paper requested the removal of the following paragraph from the penultimate version of our paper. Inclusion of this paragraph might have defused the obvious confusion over our premise about the “position” of United States’ academic cartography. We wrote:

In the length of a journal paper, unfortunately, we are unable to document the very rich cartographic activity in other countries. Cartographic programs in the United Kingdom, for instance David Bickmore at the Experimental Cartographic Unit and J.S. Keates at the University of Glasgow, Jacques Bertin at the University of Paris, activity in Germany at the Universities of Hanover and Berlin, Ferjan Ormeling at the ITC in the Netherlands, and Salichchev at the University of Moscow, and the long tradition of cartographic activity in China at Wuhan, are examples. We leave the identification, documentation, and analysis of such programs to those more knowledgeable about their significance.