GeoGraphic information SyStemS Zhang Atkinson Goodchild Scale in Spatial Information and Analysis “… an authoritative and thought-provoking account of scaling issues in spatial information and analysis. Written by leading authorities in the field, this book should be of considerable value to anyone working with spatial data by providing a contemporary account of s cale, its characterisation and analysis.” —Giles Foody, University of Nottingham, UK “… a timely addition to the growing literature on the topic of scale and change of support. … The authors have done a marvelous job of tackling this difficult topic with enough breadth and depth, producing what should become the reference in th e field for years to come.” —Pierre Goovaerts, BioMedware, Inc. “… A truly informative collection … will certainly promote the importance of scale as the importance of geography has been increasingly recognized by people while stepping into the so -called ‘Digital Earth’ big data age.” —Hui Lin, Institute of Space and Earth Information Science, The Chinese University of Hong Kong “… a cutting-edge analytical survey that presents scale in its myriad contexts, effectively linking it with cartography, spatial accuracy, spatial sampling, and spatial statistics. As such, it will set a new standard for the next round of state-of-the-art work con cerning geographic scale.” —Daniel A. Griffith, University of Texas at Dallas “… the book will serve as a long and lasting contribution to the scale aspects that are fundamental to the many spa tial problems that are covered.” —Alfred Stein, University of Twente, Faculty of Geo-Information and Earth Observation (ITC), Enschede, The Netherlands K11444 ISBN-13: 978-1-4398-2937-0 90000 9 781439 829370 K11444_Cover_mech.indd All Pages 3/7/14 9:52 AM Scale in Spatial Information and Analysis Scale in Spatial Information and Analysis Jingxiong Zhang, Peter Atkinson, and Michael Goodchild Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2014 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20140306 International Standard Book Number-13: 978-1-4398-2938-7 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. 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Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface.......................................................................................................................ix Acknowledgment ......................................................................................................xi Authors ...................................................................................................................xiii Chapter 1 Introduction ..........................................................................................1 1.1 Issue of Scale .............................................................................1 1.2 Models of Scale .........................................................................4 1.3 Scaling Up and Down ................................................................9 1.4 Book Chapters .........................................................................12 Chapter 2 Geographic Representations ...............................................................17 2.1 Geo-Atoms ..............................................................................20 2.2 Geo-Fields ...............................................................................21 2.3 Geo-Objects .............................................................................25 2.4 Hierarchical Data Structures ..................................................28 2.4.1 Quadtrees ...................................................................28 2.4.2 Hierarchical TINs .......................................................29 2.5 Discussion ................................................................................31 2.5.1 Geo-Dipoles and Spatial Interactions ........................31 2.5.2 Temporal Dimension ..................................................32 2.5.3 Scale Dependence of Representations ........................32 Chapter 3 Geospatial Measurements ..................................................................35 3.1 Framework for Spatial Sampling .............................................36 3.1.1 Spatial Sampling Design ............................................36 3.1.2 Data Supports .............................................................43 3.1.3 Spatial Resolution in Remotely Sensed Images .........44 3.1.3.1 Rayleigh Criterion .......................................45 3.1.3.2 MTF and Its Equivalent Bandwidth ...........45 3.1.3.3 Effective Radiometric Resolution Element ...46 3.2 Optical Remote Sensing and Resolution .................................47 3.2.1 Spatial and Spectral Responses ..................................47 3.2.2 Geometric Characteristics ..........................................50 3.3 Microwave Remote Sensing and Resolution ...........................55 3.3.1 Resolution ...................................................................55 3.3.2 Radar Signals, Imaging, and Distortions ...................58 3.3.3 Passive Microwave .....................................................62 3.4 Discussion ................................................................................64 v vi Contents Chapter 4 Geostatistical Models of Scale ...........................................................67 4.1 Geostatistical Fundamentals and Variograms .........................68 4.1.1 Random Fields ............................................................68 4.1.2 Variograms and Covariance Functions ......................70 4.1.3 Indicator Variograms and Transition Probability- Based Models ..........................................75 4.2 Variogram Regularization and Deregularization ....................77 4.2.1 Regularization ............................................................77 4.2.2 Deconvolution of Regularized Variograms ................80 4.3 Statistics for Determining Measurement Scales .....................82 4.4 Discussion ................................................................................87 Chapter 5 Lattice Data and Scale Models ...........................................................91 5.1 Lattice Data .............................................................................93 5.2 Spatial Autocorrelation and Its Measures ...............................95 5.3 Local Models ...........................................................................99 5.4 Discussion ..............................................................................103 Chapter 6 Geostatistical Methods for Scaling ..................................................107 6.1 Kriging ..................................................................................109 6.2 Indicator Approaches.............................................................116 6.3 Upscaling by Block Kriging ..................................................118 6.4 Downscaling by Area-to-Point Kriging ................................120 6.5 Geostatistical Inverse Modeling ............................................124 6.6 Discussion ..............................................................................126 Chapter 7 Methods for Scaling Gridded Data ..................................................129 7.1 Upscaling ...............................................................................131 7.1.1 Statistical Approaches ..............................................131 7.1.2 Mechanistic Approaches ..........................................134 7.2 Downscaling ..........................................................................137 7.2.1 Deconvolution ..........................................................137 7.2.2 Super-Resolution Mapping .......................................141 7.2.3 Subpixel Mapping ....................................................144 7.3 Discussion ..............................................................................145 Chapter 8 Multiscale Data Conflation ..............................................................147 8.1 Multivariate Geostatistics ......................................................149 8.2 Image Fusion .........................................................................154 8.2.1 Conventional Approaches.........................................154 8.2.2 Multiresolution Representations Based on Wavelets ...155 8.2.3 Wavelet-Based Image Fusion ...................................161 Contents vii 8.3 Other Multiscale Methods .....................................................163 8.4 Discussion ..............................................................................166 Chapter 9 Scale in Terrain Analysis .................................................................169 9.1 Digital Elevation Data and Their Scales ...............................171 9.2 Terrain Derivatives ................................................................176 9.2.1 Slope and Aspect ......................................................176 9.2.2 Curvature ..................................................................180 9.2.3 Secondary Properties ...............................................186 9.3 Models of Scale in Topography .............................................187 9.4 Methods for Scaling Terrain Variables .................................193 9.4.1 Upscaling ..................................................................193 9.4.2 Downscaling .............................................................196 9.5 Discussion ..............................................................................198 Chapter 10 Scale in Area-Class Mapping ...........................................................201 10.1 Area-Class Mapping .............................................................204 10.1.1 Discriminant-Space Model ......................................204 10.1.2 Methods for Mapping Area Classes .........................209 10.2 Spatial Scales and Patterns in Area Classes ..........................213 10.3 Scaling Area-Class Information ............................................219 10.3.1 Upscaling ..................................................................219 10.3.2 Downscaling .............................................................220 10.4 Discussion ..............................................................................223 Chapter 11 Information Content .........................................................................227 11.1 Information Theory ...............................................................230 11.2 Information Content in Remotely Sensed Images .................238 11.2.1 Informational Characteristics of Images ..................238 11.2.2 Information Conveyed in Images with Additive Noise ..........................................................242 11.2.3 Information in Images with Multiplicative Noise ....247 11.3 Image Resolution and Information Content ..........................250 11.3.1 Effects of Resolution on Information Content .........250 11.3.2 Information Capacity and Super Resolution ............253 11.4 Information Content in Map Data .........................................255 11.5 Discussion ..............................................................................261 Chapter 12 Uncertainty Characterization ...........................................................265 12.1 Accuracy Metrics and Assessment ........................................268 12.1.1 Accuracy in Interval/Ratio Fields ............................268 12.1.2 Accuracy in Area Classes ........................................271 viii Contents 12.1.3 Positional Accuracy ..................................................273 12.1.4 Confidence Intervals and Hypothesis Testing .........274 12.2 Geostatistical Approaches to Validation ...............................278 12.3 Analytical Approaches to Error Propagation ........................282 12.4 Geostatistical Simulation .......................................................287 12.4.1 Simulation over a Point Support ...............................287 12.4.2 Point-Support Simulation Conditional to Areal Data ................................................................291 12.4.3 Simulation over Blocks .............................................293 12.5 Discussion ..............................................................................296 Epilogue ................................................................................................................299 References .............................................................................................................309 Preface Scale can be a frustrating concept. It has multiple meanings even in a single scientific domain, and there is significant variation in meaning across domains. It underlies how we as humans perceive and act in the world, from the scale of our own bodies to that of our immediate surroundings, to the scale of life experiences, and to the scale of the cosmos. It can function as a noun or as a verb, with different sets of meanings in the two cases. It is implicit in the definitions of many properties that we work with as environmental or social scientists. Statements such as “Minnesota has 10,000 lakes” from that state’s license plate, “The coastline of Italy measures 7600 km” (CIA 2009), “This is the flattest spot in the United States,” or “This area has the world’s highest population density” are all scale specific, and yet we frequently make or accept statements such as these without specifying scale or even recognizing the importance of scale in them. This book attempts to resolve some of these issues and to alleviate some of this frustration by taking a rigorous, scientific approach to scale and its various meanings in relation to the geographic world. It covers methods for measuring aspects of scale and for changing scale through upscaling and downscaling. It discusses scale in rela- tion to the various systems that are now available for acquiring geographic data, for modeling environmental and social processes, and for visualizing phenomena and their distributions over the surface and near the surface of the Earth. This is not the first book to appear on these issues, and citations of many of the previous ones can be found at various points in this book. It will certainly not be the last, because geographic technologies are advancing rapidly, along with their impor- tance in numerous areas of human activity, and because our thinking and theorizing about scale are also in a constant state of flux. New techniques for downscaling, new methods of analysis, new models of spatial and temporal scale, and new theories of how scale affects and is affected by social and environmental processes are all likely to emerge in the next few years. Almost two decades ago the Alexandria Digital Library was funded by the US National Science Foundation as an early attempt to build an online system for search- ing, evaluating, and retrieving geographic datasets—in effect, an Internet-based map library (Smith et al. 1996). One of our first concerns in developing the library was to prioritize search criteria: what would people consider most important in searching for online data? First, clearly, was coverage in the form of a bounding box defined by latitude and longitude; second was theme, or the topic of the data; third was time, or the date of validity of the data. Missing from this list was scale: the degree of detail, since all geographic data must be generalized, sampled, or abstracted in some way, the real world being infinitely complex. Scale was considered too difficult for the average user to conceptualize, too difficult to characterize, and not of sufficient importance. We, the authors, hope this book will move us some distance in the direc- tion of resolving these issues and of promoting scale to the importance it deserves. Level of detail is surely an inescapable property of any digital representation of any ix