Assessing the Accuracy of Remotely Sensed Data: Principles and Practices, Second Edition (Mapping Science)

210 Pages·2008·8.01 MB·English

by  Russell G. Congalton

Second Edition
Assessing the Accuracy of
Remotely Sensed Data
Principles and Practices
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Second Edition
Assessing the Accuracy of
Remotely Sensed Data
Principles and Practices
Russell G. Congalton
Kass Green
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
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CRC Press
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© 2009 by Taylor & Francis Group, LLC
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Library of Congress Cataloging-in-Publication Data
Congalton, Russell G., 1957-
Assessing the accuracy of remotely sensed data : principles and practices /
Russell G. Congalton and Kass Green. -- 2nd ed.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-4200-5512-2 (alk. paper)
1. Remote sensing--Evaluation. I. Green, Kass. II. Title.
G70.4.C647 2008
621.36’78--dc22 2008030228
Visit the Taylor & Francis Web site at
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and the CRC Press Web site at
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Dedication
The second edition of this book is dedicated to our
families, including our spouses Jeanie Congalton and
Gene Forsburg: our children Ashton, Emma, and Brandon
Congalton, and our parents Bob and Janet Congalton,
John and Jean Samson, Mary Green, William and Carol
McDevitt, and Frank and Janet Forsburg. Together they
have made us much more than we would be alone. We are
forever grateful for their love, support, and companionship.
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Table of Contents
Preface .......................................................................................................................xi
Acknowledgments ..................................................................................................xiii
About the Authors ....................................................................................................xv
Chapter 1 Introduction ..........................................................................................1
Why Map? ..................................................................................................................1
Why Assess the Accuracy of a Map? .........................................................................1
Types of Map Accuracy Assessment ..........................................................................2
Critical Steps in Accuracy Assessment ......................................................................3
Organization of the Book ...........................................................................................4
Chapter 2 The History of Map Accuracy Assessment ..........................................5
How Maps Are Made .................................................................................................5
History of Accuracy Assessment .............................................................................11
Positional Accuracy Assessment .........................................................................11
Thematic Accuracy Assessment..........................................................................15
Chapter 3 Positional Accuracy ............................................................................19
What Is Positional Accuracy? ..................................................................................19
What Are the Common Standards for Positional Accuracy? ...................................21
National Map Accuracy Standards .....................................................................22
Principles of Error Theory and Cartographic Applications ................................22
ASPRS Interim Accuracy Standards for Large-Scale Maps ...............................23
National Standard for Spatial Data Accuracy .....................................................23
Guidelines and Specifications for Flood Hazard Mapping Partners ...................24
ASPRS Guidelines: Vertical Accuracy Reporting for Lidar Data.......................24
Guidelines for Digital Elevation Data .................................................................25
Positional Accuracy Assessment Design and Sample Selection ..............................25
How Is Positional Accuracy Analyzed? ...................................................................29
Review of Basic Statistics ...................................................................................29
Parameters and Statistics ................................................................................29
Estimating the Dispersal of Variables ............................................................30
Estimating the Reliability of the Estimate of the Mean .................................33
Statistics in Positional Accuracy Assessment .....................................................35
Vertical Accuracy ...........................................................................................37
Horizontal Accuracy ......................................................................................41
Summary ..................................................................................................................50
Appendix 3.1 ............................................................................................................53
Determining the Required Sample Size ..............................................................53
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Chapter 4 Thematic Accuracy .............................................................................55
Non-Site-Specific Assessments ................................................................................55
Site-Specific Assessments ........................................................................................56
The Error Matrix .................................................................................................57
Mathematical Representation of the Error Matrix .........................................59
Chapter 5 Sample Design Considerations ...........................................................63
What Are the Thematic Map Classes to Be Assessed? ............................................63
The Classification Scheme ..................................................................................64
Other Data Considerations ..................................................................................66
Continuous versus Noncontinuous Data ........................................................66
Spatial Autocorrelation ..................................................................................68
What Is the Appropriate Sample Unit? ....................................................................70
Single Pixel .........................................................................................................70
Cluster of Pixels ..................................................................................................71
Polygons .............................................................................................................72
Clusters of Polygons ...........................................................................................74
How Many Samples Should Be Taken? ...................................................................74
Binomial Distribution .........................................................................................75
Multinomial Distribution ....................................................................................76
How Should the Samples Be Chosen? .....................................................................79
Sampling Schemes ..............................................................................................79
Sampling Scheme Considerations ......................................................................80
Final Considerations ................................................................................................83
Chapter 6 Reference Data Collection ..................................................................85
What Should Be the Source of the Reference Data? ...............................................86
Using Existing versus Newly Collected Data .....................................................86
Photos versus Ground .........................................................................................87
How Should the Reference Data Be Collected? ......................................................88
When Should the Reference Data Be Collected? ....................................................94
Ensuring Objectivity and Consistency .....................................................................98
Data Independence ..............................................................................................98
Data Collection Consistency ...............................................................................98
Quality Control ...................................................................................................99
Chapter 7 Basic Analysis Techniques ...............................................................105
Kappa .....................................................................................................................105
Margfit ....................................................................................................................110
Conditional Kappa .................................................................................................113
Weighted Kappa .....................................................................................................113
Compensation for Chance Agreement ...................................................................115
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Confidence Limits ..................................................................................................115
Area Estimation/Correction ...................................................................................119
Chapter 8 Analysis of Differences in the Error Matrix ....................................121
Errors in the Reference Data ..................................................................................121
Sensitivity of the Classification Scheme to Observer Variability ..........................123
Inappropriateness of the Remote Sensing Data Employed to Make the Map .......125
Mapping Error ........................................................................................................126
Summary ................................................................................................................126
Appendix 8.1 ..........................................................................................................127
Wrangell-St. Elias National Park and Preserve: Land Cover Mapping
Classification Key .............................................................................................127
Chapter 9 Fuzzy Accuracy Assessment ............................................................131
Expanding the Major Diagonal of the Error Matrix ..............................................132
Measuring Map Class Variability ...........................................................................133
The Fuzzy Error Matrix Approach .........................................................................134
The Fuzzy Error Matrix ....................................................................................135
Implementation of the Fuzzy Error Matrix .......................................................137
Another Fuzzy Error Matrix Example ..............................................................138
Summary ................................................................................................................140
Chapter 10 Case Study
Accuracy Assessment for the NOAA Next-Generation C-CAP Pilot Project .......141
Overview of the Case Study ...................................................................................141
Design of the Accuracy Assessment ......................................................................144
What Are the Thematic Classes to Be Assessed? .............................................144
What Is the Appropriate Sampling Unit? ..........................................................145
How Many Samples Should Be Taken? ............................................................145
How Should the Samples Be Chosen? ..............................................................145
Data Collection ......................................................................................................146
What Should Be the Source of the Reference Data? ........................................146
How Should the Reference Data Be Collected? ...............................................147
When Should the Reference Data Be Collected? .............................................148
How Do I Ensure Consistency and Objectivity in My Data Collection?..........149
Analysis ..................................................................................................................149
What Are the Different Analysis Techniques for Continuous versus
Discontinuous Map Data? .................................................................................149
What Is an Error Matrix and How Should It Be Used? ....................................150
What Are the Statistical Properties Associated with the Error Matrix and
What Analysis Techniques Are Applicable? .....................................................150
What Is Fuzzy Accuracy and How Can You Conduct a Fuzzy Accuracy
Assessment? ......................................................................................................150
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