Symbolization of Map Projection Distortion: A Review

One of the most fundamental steps in map creation is the transformation of information from the surface of a globe onto a flat map. Mapmakers have developed and used hundreds of different map projections over the past 2,000 years, yet there is no perfect choice because every map projection uniquely alters some aspect of space during the transformation process. Detailed information about the type, amount, and distribution of distortion is essential for choosing the best projection for a particular map or data set. The distortion inherent in projections can be measured and symbolized much like any other map variable. Methods for symbolizing map projection distortion are reviewed, with each method described and illustrated in graphical form. The symbolization methods are collected under ten separate headings organized from simple to more complex in terms of interpretation. Most of these methods are highly effective at communicating distortion, yet they are rarely used beyond textbooks and technical documentation. Map projections and the distortions they carry need to be better understood by spatial data developers, distributors, and users. Map distortion should be carried along with map data as confidence layers, and the easily accessible distortion displays should be available to help in the selection of map projections. There is a suitably wide array of symbolization methods to match any need from basic education to research.     

Brief History of Spatial Information Policies in the United States

Slope exerts a powerful influence on the route selection processes of humans. Attempts to model human movement in hilly and mountainous terrain which have largely focused on least-time route transformations can be improved by incorporating research suggesting that humans systematically overestimate slopes. Such research suggests that cost functions derived from slope should be more expensive than time derivations alone would indicate. This paper presents a method for empirically estimating cost functions for slopes. We use the method to predict routes and paths that are more likely to be selected by humans based on their perceptions of slope. An evaluation of the method found that it successfully predicts road, track and trail locations over a variety of conditions and distances.     

Effectiveness and Efficiency of Map Symbols for Dynamic Geographic Information Visualization

The quality of dynamic map symbols plays an important role in the representation of spatial-temporal changes. This paper reports an investigation into the quality of dynamic symbols. To assess the quality of such symbols, a set of traffic flow data is used for the production of different kinds of dynamic maps, with focus on four variables, i.e. size, color, frame rate and display format. Two quantitative measures are used for analysis, i.e. deviation and response time. A set of traffic data is used for the production of dynamic maps for evaluation. The experimental results show that the size is more efficient and more effective than color for dynamic maps with the same frame rate and display format. The most efficient and effective color class number is 10 on the large format display such as 1024 × 768 pixels. And the most efficient and effective size class number is 15 on large format display such as 1024 × 768 pixels. The effective frame rate for dynamic map animation is smaller than that of the general animation on the Internet or Quick Time and AVI format video. The most efficient and most effective frame rate is 3 frames per second in the color expression and 6 frames per second in the size expression. In sum, the effective and efficient value of color, size and frame rate on large format display is less than the value on the small format display. These results suggest the frame rate should be reduced on the small format display. It is hoped that the results from this study will be of help in the design of effective and efficient dynamic map symbols for geographical information visualization.     

Relief-Model Symbolization

Relief models are difficult to symbolize graphically because traditional drafting techniques are not effective on their irregular surfaces. This note presents some of the procedures we employed preparing and symbolizing two models of the state of Vermont, one for tourism, one for classroom instruction. Room lighting, realism, and ease of application determined color selection for the model and its symbols. We created decalcomanias for model symbolization by painting or applying dry-transfer artwork to clear plastic decal film. We then dissolved the decals into the relief surface with dilute acetone. We made customized decal symbols with commercial photo-imageable dry-transfer materials.     

Animated Maps of Aggregate Data: Conceptual and Practical Problems

Predictions of the 1960s about the computer's potential to change cartography are finally being fulfilled. Dynamic maps for vehicle navigation, interactive cartographic/statistical tools, and map animation are being investigated actively. As these new environments for mapping become available, we must reevaluate past questions about transformations from reality to data and data to map. In this paper, we consider these transformation questions in the context of statistical map animation. The issues discussed were raised in producing a “map movie” depicting the spread of acquired immune deficiency syndrome (AIDS) over time. Jenks' data model concept is used as the basis for a typology of data models representing phenomena typically depicted by enumeration unit data. The typology is then used to evaluate symbolization decisions for AIDS incidence maps. Implications for symbol selection imposed by dynamic rather than static maps are considered, as are technical issues involved in producing the animation on a microcomputer platform. A hybrid symbolization method that we have termed the “chorodot” is suggested as a way to meet the constraints on symbolization imposed by animation and to represent the appropriate data model for AIDS incidence.     

ColorBrewer in Print: A Catalog of Color Schemes for Maps

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.     

Applications of Analytical Cartography

Several applications of analytical cartography are presented. They include terrain visibility (including visibility indices, viewsheds, and inter-visibility), map overlay (including solving round-off errors with C++ class libraries and computing polygon areas from incomplete information), mobility, and interpolation and approximation of curves and of terrain (including curves and surfaces in CAD/CAM, smoothing terrains with over-determined systems of equations, and drainage patterns). General themes become apparent, such as simplicity, robustness, and the tradeoff between different data types. Finally several future applications are discussed, such as the lossy compression of correlated layers, and just good enough computation when high precision is not justified.