Working with Map Projections: A Guide to their Selection / Edition 1

by Fritz Kessler, Sarah Battersby

Overview

A map projection fundamentally impacts the mapmaking process. Working with Map Projections: A Guide to Their Selection explains why, for any given map, there isn’t a single "best" map projection. Selecting a projection is a matter of understanding the compromises and consequences of showing a 3-D space in two dimensions. The book presents a clear understanding of the processes necessary to make logical decisions on selecting an appropriate map projection for a given data set. The authors discuss the logic needed in the selection process, describe why certain decisions should be made, and explain the consequences of any inappropriate decision made during the selection process.

This book also explains how the map projection will impact the map’s ability to fulfill its purpose, uses real-world data sets as the basis for the selection of an appropriate map projection, and provides illustrations of an appropriately and inappropriately selected map projection for a given data set. The authors take a novel approach to discussing map projections by avoiding an extensive inventory of mathematical formulae and using only the mathematics of map projections that matter for many mapping tasks. They also present information that is directly applicable to the process of selecting map projections and not tied to a specific software package.

Written by two leading experts, this book is an invaluable resource for anyone studying or working with geospatial data, from students to experienced professionals, and will help readers successfully weigh the pros and cons of choosing one projection over another to suit a map’s intended purpose.

Product Details

ISBN-13:	9781138304987
Publisher:	Taylor & Francis
Publication date:	05/21/2019
Pages:	317
Product dimensions:	6.12(w) x 9.19(h) x (d)

About the Author

Fritz Kessler, PhD, is a senior research associate and an associate professor at Penn State University. His primary responsibilities are teaching in the resident and online world campus environments. Some of the courses he has taught include map projections, datums, and coordinate systems, cartography, surveying, GIS, spatial statistics, and research methods. Dr. Kessler's research interests include map projections, geographic visualization, and cognitive cartography. His recent publications include a co-authored book, Thematic Cartography and GeoVisualization; an article, “Volunteered Geographic Information: A Bicycling Enthusiast Perspective” in Cartography and Geographic Information Science; two co-authored papers, “Analysis of Thematic Maps Published in Two Geographical Journals in the Twentieth Century” in Annals of the Association of American Geographers and “Cues for Interpreting Distortion in Map Projections” in Journal of Geography; a co-authored book chapter “Thematic Mapping” in The History of Cartography Project, Volume 6: Cartography in the Twentieth Century; a chapter contribution “Symbolizing America” to Mapping American: Exploring the Continent; and an authored entry “Projections” in the International Encyclopedia of Human Geography. Dr. Kessler earned a PhD in geography in 1999 at the University of Kansas, an MS at Penn State, and a BS at Ohio University. He is a member of the International Cartographic Association Commission on Map Projections, vice president of the North American Cartographic and Information Society, and a board member of the Cartography and Geographic Information Society. He was a former editor in chief of Cartographic Perspectives.

Sarah E. Battersby, PhD, is a senior research scientist at Tableau Software. Her primary area of focus is cartography with an emphasis on cognition. Her work emphasizes how we can help people visualize and use spatial information more effectively. Her research has covered a variety of areas, including perception in dynamic map displays, geospatial technologies and spatial thinking abilities, and the impact of the map projection on spatial cognition. Sarah earned a PhD in geography in 2006 at the University of California at Santa Barbara. She is a member of the International Cartographic Association Commission on Map Projections and a past president (2015-2016) of the Cartography and Geographic Information Society, a society composed of educators, researchers, and practitioners involved in the design, creation, use, and dissemination of geographic information. Dr. Battersby is also a member of the National Geospatial Advisory Committee, a Federal Advisory Committee sponsored by the Department of the Interior under the Federal Advisory Committee Act.

Table of Contents

Preface xiii

Acknowledgments xv

Authors xvii

Part I Projection Basics, Cartographic Symbolization, Projection Influences on People's Mental Maps, and Selecting Projections

1 Introduction 5

Mathematical Complexity 5

Thread 1 Ellipsoid vs. Sphere Earth Models 6

Thread 2 Projection Parameters 7

Map Projection Terminology 8

Scattered Map Projection Literature 11

Map Projections as a Map Design Variable 12

The Problem of Selecting a Map Projection 15

This Book's Structure 16

2 A Gentle Introduction to Map Projections 19

Earth's Latitude and Longitude 20

Earth's Shape and Size 22

The Map Projection Process 26

Projection Equations 27

Spherical vs. Ellipsoidal Projection Equations 31

The Map Projection Properties 31

Preserving Angles (Conformal Property) 32

Preserving Areas (Equal Area Property) 33

Preserving Distances (Equidistant Property) 35

Preserving Directions (Azimuthal Property) 38

Preserving No Specific Property (Compromise) 38

Projection's Influence on Map Design 40

The Map's Shape: The Projection Class 40

Focusing the Map's Center: The Projection Aspect 42

Map Projection Distortion 43

Distortion Patterns and Projection Class 43

Distortion Patterns and Projection Property 45

Distortion Patterns and Standard Point or Line(s) 48

Distortion Impacts on Shapes of Landmasses 52

Conclusion 55

Notes 56

3 Representing Spatial Data through Cartographic Symbolization 59

Types of Maps 60

The Map Abstraction Process 61

Conceptualizing Earth's Geographic Phenomena 64

Spatial Dimensions 64

Typology of Geographic Phenomena 65

Levels of Data Measurement 67

Visual Variables 69

Shape 69

Hue 69

Orientation 72

Pattern 72

Hue 74

Value 75

Saturation 75

Size 76

Cartographic Symbolization Methods 76

Choropleth 76

Dot Density 77

Proportional Symbol 77

Isarithmic 78

Dasymetric 79

Cartogram 81

Map Reading Tasks 81

Pre-Map Reading 83

Detection and Recognition 84

Estimation 85

Conclusion 87

4 Map Projections' Influence on Data Representation 91

Interpreting Map Projections 92

The Edge of the Map (Periphery) 98

Long-Term Impacts of Map Projection? 100

Does the Projection Look "Right" or "Wrong"? 102

Is the Overall Shape Appealing? 105

Aesthetics and Fit 108

Conclusion 109

5 Assistance Using Projection Selection Guidance Tools 113

Projection Properties of Importance 114

Geographic Location, Size, and Shape 118

Broader Design and Analytic Considerations 123

Projection Shape 123

Arrangement of the Graticule 125

Appearance of the Poles 129

Interpretability 131

Conclusion 133

Part II Projection Selection by Map Type

6 Continuously Occurring and Abruptly Changing 141

Visual Analysis Tasks 142

Impact of Projection on Choropleth Maps 143

Equal Area Projections 143

Conformal Projections 147

Equidistant Projections 147

Compromise Projections 147

Large-Scale Projections 148

Conclusion 149

7 Continuously Occurring and Smoothly Changing 151

Visual Analysis Tasks 153

Spatial Interpolation: An Initial Step in Isarithmic Mapping 154

Impact of Projections on Calculating Values for Isarithmic Maps 156

Distance Measurements 158

Datum and Grid Systems 160

Equidistant Projections 161

Conformal Projections 163

Spatial Interpolation Results 164

Impact of Projection on Design for Isarithmic Maps 165

Equidistant Projections 168

Conformal Projections 169

Equal Area Projections 171

Compromise Projections 175

Conclusion 176

Notes 177

8 Discretely Occurring and Smoothly Changing 179

Visual Analysis Task 181

Impact of Projection on Dot Maps 182

Equal Area Projections 182

Conformal Projections 186

Equidistant Projections 189

Large-Scale Projections 192

General Challenges 192

Conclusion 195

9 Discretely Occurring and Abruptly Changing 197

Proportional Point Symbols 201

Proportional Line Symbols 202

Visual Analysis Tasks 202

Impact of Projections on Proportional Symbol Maps 202

Equal Area Projections 202

Conformal Projections 205

Compromise Projections 206

Equidistant Projections 208

Map Design Considerations on Proportional Symbol Maps 211

Projection Class 212

Projection Aspect 214

Poles Represented as Points or Lines 215

Interruptions 217

Map Design Considerations on Flow Maps 219

Distance Calculation 219

Direction Calculation 221

Show the Flow Paths 221

Enhanced Visual Appearance 221

Conclusion 223

10 Special Maps 225

Spatial Bin Maps 225

Tasks for Maps Using Spatial Bins 226

Projection Considerations for Spatial Bin Maps 228

Heatmaps 234

Tasks for Heatmaps 235

Projection Considerations for Heatmaps 235

Projections for Other Special Mapping Purposes 236

Mapping Rhumb Lines 238

Mapping Great Circle Routes 240

Measuring Distances between Locations 240

Measuring Directions between Locations 241

Conclusion 242

Note 243

11 Web-Based Map Projection Resources 245

Introduction 245

Projection Tools and Applications 245

Visualizing and Selecting Projections 247

Adaptive Composite Map Projections (ACMP) 247

Projection Wizard 248

Geocart 249

ICA's Map Projection Visualization Tool 253

Visualizing Map Distortion 255

Comparing Map Projections 257

Customizing and Reprojecting Datasets 258

G.Projector-Global Map Projector 258

Flex Projector 259

Programming Languages, Libraries, and Tools for Projections 263

Common Programming Languages 263

Code Libraries 264

Tools 266

Learning about Map Projections 266

Geographer's Craft 267

Geokov: Map Projections 267

Axis Maps 267

Geocart 267

USGS Map Projection Poster 268

Radical Cartography 268

ICA's Commission on Map Projections 268

Map Projection Galleries 268

A Gallery of Map Projections 269

Map Projections-Complete Directory of Map Network Designs 269

Wolfram MathWorld: Map Projections 269

MicroCAM 269

Institute of Discrete Mathematics and Geometry: Picture Gallery of Map Projections 269

Compare Map Projections 270

Appendix 273

Bibliography 287

Index 291