GIS fundamentals

330 Pages·2014·3.887 MB·English

by  Wise, Stephen

GIS AND REMOTE SENSING
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GIS s
e Second Edition
Fundamentals
Second Edition
“Given the transition from stand-alone GIS to a crucial component in the information infrastructure
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of today’s society, the extended coverage of data management in the new version is an important
improvement. … [an] excellent introduction to the fundamental GIS concepts. … gives clear insight
into the Geo-ICT machinery to a much wider audience than just computer scientists.”
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—Prof. Peter van Oosterom, Delft University of Technology, The Netherlands
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“Steve Wise has produced a book that is a marvellous complement to GIS courses, taking
the reader on an excursion back to the fundamentals of spatial representation. Vectors,
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rasters, surfaces and networks are explained in depth and enrich the study of GIS to
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the point where students can progress their knowledge of the field to practical and professional
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applications.”
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—Michael Batty, Centre for Advanced Spatial Analysis, University College London, UK
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Maintaining the features that made the first edition so popular, GIS Fundamentals, Second
Edition provides an accessible examination of the underlying principles for anyone with no e
formal training in computer science. n
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See What’s New in the Second Edition: a
• Coverage of the use of spatial data on the Internet ls GGIISS
• Chapters on databases and on searching large databases for spatial queries
• Improved coverage on route-finding and of heuristic approaches to solving
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real-world spatial problems e
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• International standards for spatial data o
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With GIS technology increasingly available to a wider audience on devices from apps on
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smartphones to satnavs in cars, many people routinely use spatial data in a way which used d
to be the preserve of GIS specialists. However, how spatial data is stored and analyzed on it FFuunnddaammeennttaallss
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a computer still tends to be described in academic texts and articles which require specialist o
n
knowledge or some training in computer science. Using clear, concise language, but without
sacrificing technical rigour, the book gives readers an understanding of what it takes to produce
systems which allow them to find out where to make their next purchase and how to drive to
the right place to collect it.
Stephen Wise
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Second Edition
GIS
Fundamentals

Second Edition
GIS
Fundamentals
Stephen Wise
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
CRC Press
Taylor & Francis Group
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© 2014 by Taylor & Francis Group, LLC
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Version Date: 20130830
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Contents
Preface ......................................................................................................................ix
Acknowledgements ............................................................................................xiii
Author .....................................................................................................................xv
1. Introduction .....................................................................................................1
1.1 How Computers Solve Problems ........................................................2
1.2 How Computers Represent the World: Data Modelling .................5
1.3 The Structure of a Computer .............................................................10
1.4 Pseudocode and Computer Programming .....................................15
Further Reading .............................................................................................21
2. Databases ........................................................................................................23
2.1 What Are Databases and Why Are They Important? ....................23
2.2 Relational Database ............................................................................29
2.3 Storing Spatial Data in a Relational Database ................................32
2.4 Solutions to the Problems of Storing Spatial Data in RDBMS ......35
Further Reading .............................................................................................37
3. Vector Data Structures .................................................................................39
3.1 Simple Storage of Vector Data ...........................................................39
3.2 Topological Storage of Vector Data ...................................................49
3.3 So What Is Topology? .........................................................................54
3.4 And How Does It Help? The Example of DIME .............................57
3.5 More on Topological Data Structures ..............................................60
3.6 And a Return to Simple Data Structures .........................................64
Further Reading .............................................................................................67
4. Vector Algorithms for Lines .......................................................................69
4.1 Simple Line Intersection Algorithm .................................................69
4.2 Why the Simple Line Intersection Algorithm Would
Not Work: A Better Algorithm ..........................................................74
4.3 Dealing with Wiggly Lines ................................................................78
4.4 Calculations on Lines: How Long Is a Piece of String? .................81
4.5 Line Intersection: How It Is Really Done .........................................84
Further Reading .............................................................................................93
5. Vector Algorithms for Areas ......................................................................95
5.1 Calculations on Areas: Single Polygons...........................................95
5.2 Calculations on Areas: Multiple Polygons ......................................98
© 2008 Taylor & Francis Group, LLC v
vi Contents
5.3 Point in Polygon: Simple Algorithm ...............................................101
5.4 ... and Back to Topology for a Better Algorithm .........................105
Further Reading ...........................................................................................108
6. The Efficiency of Algorithms ...................................................................109
6.1 How Is Algorithm Efficiency Measured? ......................................109
6.2 Efficiency of the Line Intersection Algorithm ..............................112
6.3 More on Algorithm Efficiency .........................................................114
Further Reading ...........................................................................................116
7. Raster Data Structures ...............................................................................119
7.1 Raster Data in Databases .................................................................120
7.2 Raster Data Structures: The Array .................................................123
7.3 Saving Space: Run Length Encoding and Quadtrees ..................127
7.4 Data Structures for Images ..............................................................132
Further Reading ...........................................................................................139
8. Raster Algorithms ......................................................................................141
8.1 Raster Algorithms: Attribute Query for Run
Length Encoded Data .......................................................................141
8.2 Raster Algorithms: Attribute Query for Quadtrees .....................144
8.3 Raster Algorithms: Area Calculations ...........................................153
Further Reading ...........................................................................................159
9. Data Structures for Surfaces ....................................................................161
9.1 Data Models for Surfaces .................................................................162
9.2 Algorithms for Creating Grid Surface Models .............................166
9.3 Algorithms for Creating a Triangulated Irregular Network ......174
9.4 Grid Creation Revisited ....................................................................180
Further Reading ...........................................................................................183
10. Algorithms for Surfaces ............................................................................185
10.1 Elevation, Slope and Aspect ............................................................185
10.2 Hydrological Analysis Using a TIN ...............................................192
10.3 Determining Flow Direction Using a Gridded DEM ..................195
10.4 Using the Flow Directions for Hydrological Analysis ................199
Further Reading ...........................................................................................205
11. Data Structures and Algorithms for Networks ....................................207
11.1 Networks in Vector and Raster .......................................................207
11.2 Shortest Path Algorithm...................................................................209
11.3 Data Structures for Network Data ..................................................216
11.4 Faster Algorithms for Finding the Shortest Route .......................225
Further Reading ...........................................................................................234
© 2008 Taylor & Francis Group, LLC
Contents vii
12. Strategies for Efficient Data Access ........................................................235
12.1 Tree Data Structures .........................................................................238
12.2 Indexing and Storing 2D Data Using Both Coordinates .............244
12.3 Space-Filling Curves for Spatial Data ............................................250
12.4 Spatial Filling Curves and Data Clustering ..................................252
12.5 Space-Filling Curves for Indexing Spatial Data ...........................255
12.6 Caching ...............................................................................................265
Further Reading ...........................................................................................269
13. Heuristics for Spatial Data .......................................................................271
13.1 Travelling Salesman Problem ..........................................................272
13.2 Location Allocation ...........................................................................277
13.3 Metaheuristics ...................................................................................283
13.4 Computability and Decidability .....................................................288
Further Reading ...........................................................................................293
Conclusion ...........................................................................................................295
Glossary ...............................................................................................................297
References ...........................................................................................................305
© 2008 Taylor & Francis Group, LLC

Preface
When I set out to design a GIS course for third-year undergraduates in
the Department of Geography at Sheffield University, I decided to include
some material on how GIS worked at a fundamental level. The students
were already familiar with how to use GIS from earlier courses, and so the
next obvious step was to understand how they worked. An analogy which
I often use is that they knew how to drive the car – now it was time to learn
how the internal combustion engine works. The problem I faced was that
there was very little reading that I could provide for them which was at a
level that they could understand. Some of the early work in GIS was under-
taken by geographers, but modern GIS systems draw on ideas developed
in mainstream computer science. This makes the literature difficult to fol-
low for anyone without a background in this discipline, although the tech-
niques used to store and process spatial data are not fundamentally difficult
to understand. I decided to solve my problem by writing my own book,
and this is how the first edition of GIS Basics came to be produced. In the
years since it was published, there has been an explosion in the use of spa-
tial data so that, from being a specialist area, GIS technology is now some-
thing which is used via technologies such as the Internet, GPS and mobile
phones by huge numbers of people on a daily basis. It therefore seemed
timely to update the book to reflect some of these changes. The name has
been changed to GIS Fundamentals to better reflect the fact that this is not an
introductory text. However, the aim remains the same, which is to provide
an introduction to some of the main ideas and methods that underpin GIS
in simple, everyday language.
Learning Features
The book does not attempt to be comprehensive or exhaustive and is delib-
erately written to be readable and accessible. When a detailed explanation
would interrupt the flow of the text, it is provided in a separate box. The book
can be used by students in two ways:
1. To deepen your knowledge of GIS by understanding in more depth
how GIS works. If this is your aim, then you may find that the book
is sufficient in itself. While not exhaustive, the coverage of material
is quite broad.
© 2008 Taylor & Francis Group, LLC ix