Gis Manual Self Learning

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GIS Manual Index File

A SELF TEACHING STUDENT'S MANUAL FOR GIS

Module 1. Geographic Information Systems

Module 2. Raster GIS: An Introduction

Module 3. Vector GIS: An Introduction

Module 4. Managing Attribute Data in GIS

Module 5. Integrating Remote Sensing with GIS

Modules written by

George ChoPh.D.Associate Professor, School of Resource, Environmental & Heritage Sciences

ivision of Science and Design Univeristy of Canberra, ACT 2601, AUSTRALIA.

Citation

o reference this material the correct citation for this page is as follows:

ho, G (1995) A Self-Teaching Student's Manual for Geographic Information Systems. (Insert here the Moduleumber and Name)Canberra: University of Canberra and CAUT. Online URL, http://infosys-

aw.canberra.edu.au/gismodules/index.html, as of (...) [date and time].

end an e-mail message to [email protected] if you have comments and suggestions to make about this web site.

opyright 1999 George Choast updated: Feb 12, 2001

Information System Law | Research Group| e-Business Law | Research Projects|

Publications| GIS Teaching Modules| GIS Links| News|Conferences| e-Mail Contact

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GIS_Module 1--tabl_introduction

GEOGRAPHIC INFORMATION SYSTEMS

MODULE 1[Home][Comments] [Modules] [Glossary]

TABLE OF CONTENTS

Preface

Acknowledgments

Introduction

Materials require

Aims

Objectives

I. Geographic, Information and Systems

1.1 Definition

1.2 A Simple Approach

1.3 Geographic and Geographical

1.3.1 Locational and Spatial Questions

1.3.2 Spatial Patterns and Spatial Processes

1.4 Information1.5 Systems

1.6 A Quick Quiz

2. GIS: What, How and Why

2.1 A Brief History of GIS

2.2 GIS and Other Disciplines

2.3 Applications of GIS

2.4 A Critique of GIS

2.5 Another Quick Quiz

3. GIS: Nuts and Bolts

3.1 Basic Elements

3.2 GIS Viewpoints

3.3 GIS: Basic Questions

3.4 Requirements of a GIS

Summary

Further Reading

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Revision

Working with PCs

Glossary.

PREFACE

Geographic Information Systems is the first of five modules in the series on A

Self Teaching Students Manual for GIS. This manual is the result of workundertaken for a Committee for the Advancement of University Teaching(CAUT) National Teaching Development Grant for 1995. Four other modulesfollow this which address raster systems, vector systems, managing attributedata and integrating remote sensing with GIS. In order to complete this self-contained unit successfully users should be prepared to spend approximatelyten hours, that is, reading and working with the manual, writing up results, doingextra reading and attempting an assessment exercise. We guarantee that youwill have achieved the aims and objectives of this module if you abide by the

instructions given in the best practice guarantee agreement appended below!

The presentation style given in this and following modules is one which may bedescribed as a spiral curriculum. In such a curriculum, the contents in thepresent module are used again in a following module except in more depth anddetail the next time the same or similar concepts are encountered. In general,there are four parts to a module:

1. the text presents both the conceptual and practical aspects of themodule with examples from as many usages as possible;

2. diagrams, figures and other illustrative materials are used to explain andshow relationships;

3. questions, exercises and problems to be solved and an assessment;and

4. suggestions for further reading and research. (See curriculum chart inFigure 1.1).

.

Figure 1.1 Interlocking modules of the spiral curriculum



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It is advisable that you use thisworkbook as your personal notepad. Ahighlighter or bright coloured biro tounderline text will help identifyimportant points. In this workbook allimportant concepts, words and phrasesare set out in bold letters and thosewords and phrases used which carry

different meanings from their usual areitalicised. To begin with you shouldbrowse through this workbook veryquickly just to get a feel of its contents.Reading this preface helps!

A tutor may walk you through thisworkbook but the pace may or may notsuit you. You should try to go throughthis workbook at a pace with which you

are comfortable with.

The appendices are an important component of the overall modulebecause they contain important tools. Hints on using computers, aglossary, an index, and some answers to workbook problems are provided

here.

Geographic Information Systems

Your Guarantee*

Geographic Information Systems will:

q be one of the most interesting units that you will do at this University;q change the way you look at locations and space and your place in it;q give you a solid foundation for spatial studies in applied science;q be intellectually stimulating and physically challenging; and,q take up a great deal of your time and energy over the semester.

*This guarantee is invalid if:

a. you do not study for at least ten hoursin additionto the ten hours you willspend going through this Manual; or

b. you do not ask the tutors about anything you do not understand; orc. you do not accept responsibility for your own work habits, attitudes and

learning situations.

George Cho



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Adapted from an idea by John Dearn (pers. comm. 1995).

ACKNOWLEGMENTS

I wish to thank the grants committee of CAUT for giving me this opportunity toprepare the student manuals and to contribute to the dissemination ofknowledge in geographic information systems. The CAUT grant also enabled

me to use the services of Tom Harradine as a research assistant who was ablenot only to learn the subject-matter very quickly but also to help assemble thereading material, prepare the computer software and necessary data andgenerally to bring this project to fruition. Colleagues and students in the Schoolof Resource, Environmental and Heritage Sciences and the Faculty of AppliedScience and the Faculty of Environmental Design, University of Canberra

provided a very stimulating learning and teaching environment.

I should also like to thank the following individuals and publishers for permissionto reproduce their illustrations and examples in this workbook.

John Dearn Concepts in Biology Handbook, 1995;Abler, R.S. Adams, J.S. & Gould, P. (1971)Spatial Organization, New Jersey: Prentice Hall, Figure 3-2, p. 57; Figure 3-18, p. 77; Antenucciet al. (1991) Geographic Information Systems: A Guide to the Technology, New York: Chapman& Hall, Figure 8-13, p. 174; Berry, B.J.L. (1964) Annals, Association of American Geographers,v. 54, pg. 5; Dangermond, J. (1990) in Peuquet, D.F. & Marble, D.F. Introductory Readings inGeographic Information Systems, New York: Taylor & Francis, Figure 3 p. 36; GIS Tutor 2Overview(1993), London: Longman, p.5; Maguire, D.F. (1991) in Maguire, D.F., Goodchild,M,F. & Rhind, D. (eds.) Geographical Information Systems, London: Longman, p. 13 Figure 1.1.

INTRODUCTION

This first module on geographic information systems (GIS) is an important onebecause it is the fundamental building block for all other workbooks that follow.Module 2, for example, deals with raster systems while Module 3 is devoted tovector systems. Both these are different ways of handling data in a GIS. Forexample, any irregularly shaped area may be represented on a paper map ashaving a certain dimension of shape, size and orientation. In a GIS such an

area can be set out in vectorform or in a raster. A vectoris a line whichrepresents the sides of an area and has a certain length and direction. A raster,on the other hand is portrayed in a grid pattern of regular dimensions, with eachcell having certain values of colour intensity or shading to depict differentdensities which together form a discernible picture. In Module 4, how tomanage the attributes of a map or a database is introduced since suchattributes are an important component of any GIS. Finally, in Module 5 theintegration of remotely sensed data and imagery with GIS is presented giventhat the latter is a technology driven by data.

This workbook will be presented in three parts. The first section will concentrateon the different components of the trilogy of words geographic, informationand systems. Then a second section will discuss what constitutes a GIS, howthey work, how they are used and to what benefit. In section three particular



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issues concerning GISs are discussed including the hardware and softwareinvolved, data availability in terms of spatial data and data models, topology andBoolean arithmetic with spatial objects, analytical capabilities of GISs, functionsand opportunities. At the end of each section there will be some quiz questionsassociated with that particular section. An assessment exercise concludes thisworkbook. Work on a computer and demonstrations are included to introducenewcomers to the hardware, software and related commands.

MATERIALS REQUIRED

q Bright coloured biro or highlighter.q Sharp pencils, preferably HB (hard-black), rulers, erasers.q A4 mm graph paper, tracing paper.q Access to a personal computer (Intel-based IBM-compatible PC).

AIMS

This module aims to provide students with the following:

1. Understand what geographic information systems (GIS) are in its manyforms and guises and their applications.

2. Appreciate and understand the many uses of GISs through examplesand demonstrations.

3. Gain a knowledge of the history of and the disciplines contributing toGISs and the directions of future development.

4. Evaluate the capabilities and short-comings of GIS from a study of its

basic components.5. Comprehend the hardware, software, technical and organisational

issues required to support and implement GISs in a work-place.6. Excite students to the possibilities and potentialities of this new

information technology tool for maintenance, planning and decision-making in any area of application.

7. Appreciate the use of computers in processing spatial information.8. Develop work skills related to using computers in any environment

data processing, word processing and mapping techniques.

Objectives

As a result of completing work related to this unit students should be able toundertake the following tasks with a certain level of understanding andcompetence.

1. Describe the various types of GISs and their applications and todifferentiate GISs from mere data banksand mapping packages.

2. Explain the various applications and uses of GIS.

3. Relate the history and development of GIS and the various disciplineswhich have contributed to this technology as well as provide an informedassessment of the future directions of this new tool.

4. Provide an objective assessment of the capabilities and relative meritsof a GIS.



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5. Evaluate the relative needs of different systems in terms of hardware,software and other technical requirements as well as some of themanagement and organisational issues in implementing a GIS.

6. Communicate the possibilities and potentialities of this new informationtechnology tool in a lively and animated way.

7. Use computers uninhibitedly and imaginatively for any tasks without fearof embarrassment or loss of face, or inhibitions of any kind that mayoccur in face-to-face teaching and learning situations.

8. Home computer skills to a high level of competence through constantpractice and adopt best practice work habits.

Send an e-mail message to [email protected] with your

comments and suggestions about this web site.ISBN 0 85889 4793 Copyright 1995 George Cho

Last updated: Feb. 13, 2001

[Home][Comments] [Modules] [Glossary]

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MODULE 1 Chap1A

GEOGRAPHIC INFORMATION SYSTEMS[Home][Table of Contents][Comments] [Modules] [Glossary]

1 GEOGRAPHIC, INFORMATION AND SYSTEMS

1.1 DEFINITION

Geographic information systems (GISs) mean different things to different people from the simplistic tothe perverse. To some, a filing cabinet containing maps of different kinds represents a GIS in its mostbasic form. However, while the information on the geography of places is all there in the maps it maynot be readily useable because of the way the information is depicted on the maps. Hence,relationships between places and things are not easily apparent to the unschooled. On the other hand,a GIS may seem to be part of a government information system or a new fangled alphabet soup ofnew information technology that is understandable only in acronyms and jargon of the trade.

There is no one definition of a GIS because the experts themselves are in disagreement as to what toinclude and/or exclude in the definition. Thus, in order to appreciate these differences, listed below aresix contrasting definitions which have been selected to highlight the importance of different aspects ofGIS as perceived by various authors over time.

Tomlinson (1972: ii) definition.

not a field by itself but rather the common ground between information processing andthe many fields utilizing spatial analysis techniques...One class or category ofinformation system and is therefore defined by specifying the particular characteristics

that would qualify an information system as geographical.

Rhind (1981: 17) definition.

[a term] normally used to describe general-purpose and extensible computer facilitieswhich handle data pertaining to areas of ground or to individuals or groups of peoplewho can be defined as living or working in specific geographical locations....The term isrestricted to those computer systems which have the capability to interrelate data setspertaining to different variables and/or to different moments in time.

Lord Chorley(1987: 132) definition.

a system for capturing, storing, checking, manipulating, analysing and displaying datawhich are spatially referenced to the Earth.

Goodchild & Kemp (1990: 1) definition.

a particular form of Information System applied to geographical data...A system of

hardware, software and procedures designed to support the capture, management,manipulation, analysis, modeling and display of spatially referenced data for solvingcomplex planning and management problems.

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MODULE 1 Chap1A

Environmental Systems Research Institute (ESRI) (1990: 1-2) definition.

an organised collection of computer hardware, software, geographic data, andpersonnel designed to efficiently capture, store, update, manipulate, analyze and displayall forms of geographically referenced information ... a computer system capable ofholding and using data describing places on the earths surface.

Epstein (1990: 490) definition.

a tool for decision-making and an aid for planning and development, consisting of adatabase containing spatially referenced land-related data, as well as the proceduresand techniques for systematically collecting, updating, processing and distributing thosedata.

In reproducing the definitions above, there is no value judgement that any one definition is better thanthe other much less that any one definition provides a final statement on the matter. Also as the list ishighly selective there is no implication that any of the other definitions used by various authors, say, in

Maguire, Goodchild & Rhind (1991), are unmeritorious. Rather, the listing usefully demonstrates thedevelopment of the discipline as a tool and aid, as part of a computer and Information System and oneclass of information systems using information processing and spatial analysis techniques. The listingalso shows how GIS has developed and changed from strictly academic pursuits in research to onewhich has become a useful tool, an activity and as a scientific art of handling spatial data. In sum, thereis no single definition of GISs save to say that it is a collective noun embracing the tools of scientificanalysis and the use of computers, applications and concepts.

1.2 A SIMPLE APPROACH

One of the many ways in which to develop a deeper understanding of the various definitions of GIS isto disaggregate each word in G.I.S. itself and proceed from there. In this single word associationanalysis it would require one to think carefully about each word by itself and how it relates as part of thecollective noun. This would involve an examination, firstly, of what kinds of issues would arise from,say, purely geographic themes. Giving incorrect map locations would be an issue or giving wrongdirections as a navigator in a car would lead many a family to distraction. Secondly, informationthemes could be analysed not only for its content but also for the primary sources from which thesedata are derived. Finally, the systems part of the noun suggests how the geography and theinformation fit together in a systematic whole. This is important in helping to build the conceptualframework from which to hang our ideas but also to see how the technology may be used in the socio-economic environment.

1.3 GEOGRAPHIC AND GEOGRAPHICAL

Both geographic and geographical are adjectives derived from the root word geography meaning thestudy of the Earth (from the Greek word geo= Earth, and graphos= study or describe). Thus, whilegeographic means of or relating to geography, geographical has the connotation of belonging to orcharacteristic of a particular region (Websters New Ideal Dictionary, 1978: 211). Most authors prefergeographic in GIS although one significant publication has used geographical in the title of the work

(Maguire, Goodchild & Rhind 1991). Here it is immaterial whichever shade of meaning is preferred orused because the following provides not only an outline of words associated with the study of the Earthbut also those features and characteristics that make any place special, different, distinctive and uniquein the geography of a place.

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For nearly 2,200 years of its existence as a discipline geography has been concerned primarily withaccurately describing the location of places. Until the basic task of accurately mapping places on the

earths surface was completed, geographers had little time or interest in asking what existed at placesand why. This was because so much of the earth was unknown and uncharted. Once the basic taskwas completed and the Western world kept expanding beyond its boundaries and filling the world map,by about the early 19th C. geographers then turned their attention to describing places and telling uswhat occurred at places and why. Thus, the familiar themes of quiz competitions, for instance questions

on naming the highest mountains, the longest rivers and capital cities of exotic places became part andparcel of many a geography lesson in the 1940s and 1950s. Such descriptive geography gave way inthe early 1960s to a quantitative revolution in geography which saw the introduction of analyticalmethods and the drawing of spatial relationships between phenomena distributed on the earthssurface. It is here that the new spatial context of GIS and its related computer technology comes intoplay. Yet, the basic questions of geography have not disappeared. Indeed, these questions havebecome even more important given that they can be better defined in both relative and absolute terms.

1.3.1. Locational and Spatial Questions

A basic geographical question is: Why are spatial distributions structured the way they are? Thisquestion is fundamental to the science of geography because it implies both a spatial distribution and aspatial process (Abler, Adams & Gould 1971: 56). A spatial distribution is the frequency with which

something occurs in a space. Such distributions may be in one-, two-, three- and n-dimensional spaces;that is, length, breadth, height and n-dimensions in hyper-space respectively. Time is sometimesconsidered as the fourth-dimension.

Histograms are often used to describe distributions in one-dimensional space. By placing a cell along

a line (one axis) each time a value is observed we produce a two-dimensional visual expression of thefrequency of occurrence of a variable in one-dimensional numeric space(See Figure 1.2a). In two-dimensional numeric space the same principles apply except there are two axes (plural of axis) insteadof one and for each observation there are two variables x, y to plot. Here we produce a scatter plot(Figure 1.2b). This is useful because it gives the nature of any systematic relationship between the twovariables in numeric space. It is also a starting point for further analysis of the distribution of aphenomena. The x, and y-axes can also be thought of as latitude and longitudes which define terrestrialspace. Distributions may also be observed in three-dimensional statistical space or terrestrial space.Plotting an observation according to three variables such as latitude, longitude and height produces adistribution in three-dimensional space(Figure 1.2c). It is difficult to visualize more than threedimensions but mathematicians and physicists tells us that 4, 6, 10 or n-dimensions ofhyperspacesdoexist.

Figure 1.2 Spatial distributions in numeric space



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The two things to note here are:

(1) a distributionis the frequency of occurrence of a phenomena in space, and

(2) the scale at which a space is examined determines the nature of the distribution.Spatial distributions may be composed of like or unlike things; and they may be ubiquitous (found

everywhere) or localized. Areal variation that describes the spatial differences in occurrences (that isspread of a phenomena over space) and density (that is, concentration of the phenomena in oneplace), is characteristic of almost all distributions in terrestrial space. Spatial differences in occurrencemanifests itself as a pattern while density may be shown as a variation in intensity from place to place.



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The geographical scale of analysis of any distribution is that which is observable at the local toterrestrial scales.

The question ofwhere is basic to all geography. But this question can be answered in an absolute anda relative way. Absolute location is a position in relation to a conventional grid system designed forlocational and navigational purposes. Canberra, for example, is located at 35 17 south latitude and149 08 east longitude using the Australian Map Grid (AMG). Another description of absolute locationis a street address, viz. 90210 Melrose Place, Philip, ACT 2610. The description of the apartment at

this place is its site, that is, the plot of ground that it occupies. In both these examples, it enablesanyone to find it easily because these do not change through time and are part of an imaginary networkof places. The only difference is that the first example is based on a small-scalemap whereas the lattermust of necessity be based on a street map, a large-scalemap.

The concept of small-scale and large-scale maps need a short explanation. Consider a football fieldmeasuring 100 meters on a side. On a map of 1:10,000 scale, the field is drawn 1 centimetre on a side.On a map of 1:100,000 scale, the field is drawn 0.1 millimetre on a side. The field appears largeron the1:10,000 scale map; we call this a large-scalemap. Conversely, the field appears smaller on the1:100,000 scale map and we call this a small-scalemap.

Relative location is a position with respect to other locations. For example, the University of Canberrais 14 kilometres north-west of Civic or that it is situated between Civic and Belconnen (that is, itssituation). We may also say that Canberra is about three hours driving time south-west of Sydney. Suchrelative locations and distances can also be expressed in the cost of travel between two places, thetravel time it takes or the cost of a long-distance phone call. Because these measurements are relativetheir location can be said to be changing also. For example, in the 17th C. it took about six months ormore to travel from Liverpool, England to Sydney, Australia but today it would take about 30 hours byjet and much less with supersonic aircraft and communicate just about instantaneously by electronicmeans. This phenomena has been described as a time-space convergencewhere distant places are

brought closer together through modern technology and the term Global Villagehas sometimes beenused to describe the shrinking world in so far as communications is concerned.

1.3.2. Spatial Patterns and Spatial Processes

When the internal organisation of a distribution in space is examined it may be observed that there is apattern in the location of the elements of the distribution relative to one another. The pattern may bedescribed as dense, sparse, agglomerated, dispersed and linear. This internal relative location ofelements has been called a spatial pattern orspatial structure the location of each element

relative to each other and the location of each element relative to all others taken together. Spatialprocesses are the mechanisms which produce the spatial patterns of distribution over time.

As mentioned previously in the new spatial context relative location and relative distance define a newway of dealing with stretchable and shrinkable spaces as if these locations were drawn on a rubbersheet either under tension or stretched. In the former when the tension is released two locations can beseen to have moved physically closer together whereas in the latter the locations move apart when therubber sheet is stretched. (See Figure 1.3).

Figure 1.3 Rubber sheeting example



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MODULE 1 Chap1A

Source: Antenucci et al. (1991: 174).

Figure 1.6 Population Space: A cartogram showing United States in proportion to population, 1 July1967.



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MODULE 1 Chap1A

Source:Abler, Adams & Gould (1971: 77 Figure 3-18).

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Copyright 1999 George Cho


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Module 1 Chap1B


[Home][Table of Contents][Comments] [Modules] [Glossary]

1.4. INFORMATION

GISs are a technology fed by data. Raw data are transformed into information through initialprocessing. This implies that the data, as the basic components of a library of data a data bank are in the form that is useable by computers. When the data are converted into machine-readableform, invariably as a set of digits, they become digitaldata. The raw data may come in a variety ofnumericscales of measurement nominal, ordinal, interval and ratio.

nominal nom(French for name) identifies observed differenceswithout putting a quantity, for example, a suburb, district ortown centre

ordinal involves ranking, greater than (>) or less than ( C > A < D < E

interval allows the difference between adjoining pairs in sequence tovary thus: B < C by 1.4, A < D by 2.8 etc. But because thereis no true zero in this scale we cannot conclude that D istwice as attractive or beautiful than B.

ratio preserves the ratio between numerical observations as wellas between intervals. There is a true zero, for example, theKelvin scale for temperature. On the Kelvin scale 20K istwice as hot as 10K.

In the context of processing therefore, when the data are ordered in some way to make it intelligibleto humans we then have the beginnings ofinformation. Ironically, in the form of information, it is

neither necessary that computers are required nor are they an essential part of the context. Thischaracterisation of data and information may be taken to higher levels of abstraction so thatinformation is derived knowledge and the sum of all knowledge provides an intelligence to thescheme of things. Indeed, it is sometimes claimed that wisdom is the correct use of knowledge.

Figure 1.7 The hierarchical relationship between data, information, knowledge and wisdom

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Module 1 Chap1B

A cardinal rule in scientific inquiry is that the observations that we make should be done in such away as to lead others to obtain the same results. The data that we collect should build up preciseand systematic information about our subject rather than result in a series of random impressions.There are a number of ways in which the data and information may be put together so thatrelationships and associations may be observed and the results shown in a graphical or tabular form.Thus, the orderly arrangement and display of a set of observations can be thought of as a

descriptionof a subject-matter under study and these are usually put in words or verbal form.Geographers have relied on mapsas a means of description. More recently, emphasis is onnumerical description and the map is replaced by a matrix. A matrix is any ordered table withnumerical information occupying the cells. The general form of a geographical data matrixmay thusbe illustrated and explained (see Figure 1.8).

Figure 1.8 A geographical data matrix



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Module 1 Chap1B

Source: Berry, B.J.L. (1964) Approaches to regional analysis: A synthesis, Annals, Association ofAmerican Geographers, v. 54, pp. 2-11.

Along the vertical axis are the units of observation places, locations or areas numbered in asequence. Along the horizontal axis are the conditions on which observations are taken, againnumbered in sequence and these are referred to as the variablesorattributes. They are variables

because one observation may vary from the next, and they are attributes measured on a nominalscale since each observation may have distinctive features or characteristics. Each cell in the matrix

will be occupied by a number and depending on the scale of measurement can indicate the presenceor absence of an attribute measured on a nominal scale, the rank of the unit of observation if ordinalmeasurement is used or the magnitude of the observation on a variable using an interval or ratioscale.

This matrix is therefore rich with information when completed. A column of the matrix will show asingle distribution pattern and how this variable varies between areas or locations. A row of thismatrix indicates the character of a particular place in terms of all the variables and attributescollected about this place. A third dimension may be added to represent changes through time, thatis, the trends and processes which change either from place to place or of the variables and

attributes observed.

Any geographical pattern may also be depicted as a matrix points, lines or areas. These threerepresentations have been used as the building blocks for a geographically based information

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system. Each of these data types can be represented in one of seven ways feature data, arealunit information, network topological data, sampling data, surface information, label text information,and graphic symbol data (see Figure 1.9). The word polygonis used here and is synonymous with

area. In formal terms a polygon is simply any irregularly shaped figure with five or more sides.

Looking at the geographical patterns in both matrices presented above helps put in focus importantissues arising from any study. These are: what units of observation are to be used, what conditionsare to be studied, when, and what units of measurements should be used?

One final observation before concluding this section on information may be necessary. When wecollect data and then place them into some order so that they become understandable, wesometimes combine the observations into groups. These groups are made as homogenous aspossible because we are trying to generalize the data. Say we are collecting data on the number oftrees in any area, we may choose to classify these data in terms of the density, that is, the number oftrees per unit area. Plotting a map showing the tree density will be very informative because it maylead us to ask questions about the soil type underlying some area, proximity to water, slope of theland and so on. This map can be more useful than simply a plot of the location of each tree.

Figure 1.9 Breakdown of geographic data types and methods of representation

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But here we encounter a basic paradox. The map based on tree density containsless informationthan the map showing the location of trees. In classifying trees according to density we loseinformation through the process of generalisation. We cannot tell from this density map where eachtree is located. Yet, this density map conveysinformation more readily than the tree location map.The conclusion is that the raw data often contains more information than we can comprehend andtrying to discover relationships among the raw data usually produces a condition ofinformationoverload. Thus, what we need to achieve is some balance between too much information andgeneralising information to the point that it becomes meaningless.

1.5 SYSTEMS

Systems is the final word in GIS which requires a short discussion. The word systems has becomeheavily clich-ridden in the sense that nearly every scientific discipline uses the term to describe amethodology, a technique or a process. Some have considered the systems view as potentially avery powerful analytical tool. The use of the word in GIS suggests an analogy to an organism as anadaptive system, speaking of system boundaries, articulation with the environment, homeostasis(stability), equilibrium and regulation.

Consider the following discussion of an information system.

An informationsystemcan be conceived of as a set of interrelated structures that

receive an inputof data through receptorsand process this data by comparing it tomemoryand values and submitting it to decision. Decision leads to storage of data inmemory, and if appropriate, to implementation of decisions through effectors. Thisaffects the environmentbeyond the system boundaries, causing feedbackas part ofthe data input of the next phaseof the input-transform-outputprocess.

Moreover, this information input may contain unneeded information ornoise, as wellas information at varying levels of importance. For this reason the receptors mustscanand selectdata received prior to processing. This selectivity introduces thepossibility ofperceptual biasesand errors, especially as the loadof data input

increases. Load may also involve eitherlag in processing or reduction of lead inforecasting from received data (Garson 1971: 51).

In an overview Marble (1984: 19) tabulated the major components of a GIS to contain the following:

1. A data input subsystem which collects and/or processes spatial data derivedfrom existing maps, remote sensors etc.

2. A data storage and retrieval subsystem which organizes the spatial data in aform which permits it to be quickly retrieved by the user for subsequent

analysis, as well as permitting rapid and accurate updates and corrections to bemade to the spatial database.3. A data manipulation and analysis subsystem which performs a variety of tasks

such as changing the form of the data through user-defined aggregation rules orproducing estimates of parameters and constraints for various space-time



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optimization or simulation models.4. A data reporting subsystem which is capable of displaying all or part of the

original database as well as manipulated data and the output from spatialmodels in tabular or map form. (See Marble 1984).

Figure 1.10 Components of a GIS. A simplified overview

To be considered a true GIS, the softwaresystem must include all four of the functionsnoted above and must perform efficiently inall four areas. Thus, digitizing systems whichconcentrate on data capture with minimaldata storage / retrieval capabilities, remotesensing and image processing systems andthematic mapping systems do not qualify asGISs because one or more of the fouringredients are missing. In future it is thoughtthat modelling capabilities should be includedas a mandatory function of any true GIS(Marble 1984: 19).

1.6 A QUICK QUIZ

1. Examine the various definitions of GIS. What do you learn about the diversity of definitions ofGIS?

2. Can you find other definitions of GIS from the perspectives of (a) applications, (b) functions,and (c) system structure.

3. Think of the cricketers worm frequently seen on TV. The number of overs bowled are givenon the x-axis and the runs are on the y-axis. Is this a scatter plot? One- or 2-dimensions?Can any meaningful statistical analysis be performed on such a plot? Why and why not?

4. Differentiate between terrestrial, statistical and numeric space. Give examples.5. Give examples of occurrence and density of spatial distributions that you have come across.

6. Is a 1:1 million map a large- or small-scale map? Explain this to someone.7. When we have a scale of 1: 50,000 we mean 1 centimeter on the map is 50,000 centimeterson the ground. Equally, we could also have said that 1 millimeter on the map is equal to50,000 millimeters on the ground. Both are correct ways of expressing the scale of the samemap. Explain how this is true.

8. Find out what is a representative fraction. Express this in both words and numbers.9. Give a real-world example of how two locations may move apart in relative terms.

10. What is the minimum permissible personal space that we are allowed in conversation. Is thisa physical space or a perceptual one?

11. Examine Jack Dangermonds (1990) figure (Fig. 1.9 page.1- 21) very carefully. Study each ofthe entries in the 21 cells. Are there any overlaps in the cells? Can you think of anyomissions? Where would you place the following in the matrix: a bus stop, a hockey field anda street name.



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"center">GEOGRAPHIC INFORMATION SYSTEMS[Home][Table of Contents][Comments] [Modules] [Glossary]

2. GIS: WHAT, HOW AND WHY

n a GIS geographic data are referenced in such a way as to allow its retrieval, analysis and display on any spatial criteria.These tasks are handled by data processing subsystems, data analysis subsystems and information use subsystems. TheGIS therefore is an integrated set of computer programs for handling spatial data. There are of course various terms which

ave been used to describe this technology (see Table 1.1). In this section we will discuss a short history of GIS, the otherisciplines that contribute to and use GISs and some applications of this new technology. A critique concludes thisection.

Table 1.1 Other terms used to describe Geographic Information Systems

Automated GIS (AGIS)Automated Mapping & Facilities Management (AM/FM)

Computerised GISEnvironment Information Systems

Geo-Information SystemsGeographically Referenced Information Systems

Image Based Information SystemLand Information Systems

Land Resources Information SystemsMultipurpose Cadastre

Multipurpose Geographic Data SystemMutipurpose Input Land Use System

Natural Resource Management Information SystemPlanning Information SystemsResource Information SystemSpatial Information Systems

System for Handling Natural Resources Inventory Data

.1 A BRIEF HISTORY OF GIS

The initial attempts to apply computer technology to handle the problems encountered with the use of spatial data weressociated with military applications. Such efforts were very productive of results but at the cost of using massiveomputing resources. These early problems were also associated not only with the low level state-of-the-art in computerechnology but also the special problems encountered with digital spatial data. In the mid-60s the first serious attempt toandle substantial amounts of spatial data using computers was instituted in the Canadian Geographic Information

System (CGIS). It is still in operation and remains one of the most cost effective examples of large-scale spatial dataandling. In the beginning all spatial data handling systems were custom-built, but in the late-70s general purpose,urnkey systems began appearing and today the use of such systems is the rule rather than the exception. Turnkey is aerm used to describe off the shelf computer systems without any customisation or modifications. The system operates athe turn of a key.

The purpose of CGIS was to analyze the data collected by the Canadian Land Inventory (CLI) and to produce statistics toe used in developing land management plans for large areas of rural Canada. The CLI created maps at a large-scale of:50,000 which classified land using various themes, for example, soil capability, recreational potential, wildlife, forestrynd present land use. The CLI produced seven primary map layers each showing locations or areas with homogenousttributes; other map layers were developed subsequently. Among the technological innovations were the development of

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ew technology because no one had had previous experience in this area and there was no precedent for performing GISperations such as overlays and area measurement. The high cost of technical development landed the project in trouble

when it failed to deliver promised products and capabilities. The completion of a database and the generating of productsy the mid-70s established CGIS as a model of technological excellence despite its aging database. Attempts were made

o adapt the system to new data and the addition of new functionality with remote access and networking, but these effortsave failed to compete with new vendor products of the 1980s and 1990s. (Refer to Goodchild, M.F. & Kemp, K. (eds.)1990) Introduction to GIS, NCGIA Core Curriculum, Unit 23: History of GIS, Santa Barbara, CA: NCGIA, pp. 23-1 - 23-9).

The ODYSSEY System was designed by the Laboratory for Computer Graphics and Spatial Analysis at Harvard

University. It was developed in the mid-70s and extended earlier Harvard programs beyond format conversion to aomprehensive analysis package based on vector data and provided algorithms(a kind of mathematical formula) forolygon overlay and sliver removal. Slivers result when lines drawn over each other produce tiny sections of non-overlap

when what was intended was simply one neat line. Slivers are also known as digitizing errors because they occur whendjacent polygons overlap. Sometimes the opposite may also occur during digitizing and gaps appear between adjacentolygons.

An early Harvard program called SYMAP was developed as a general mapping package. The output was exclusively on ane printer hence its low resolution and poor quality and limited functionality. But it demonstrated that a computer could

make maps and sparked intense interest. (See Figure 1.10 for an example of a SYMAP output).

n the late 1960s CALFORM was developed to produce SYMAP maps on a plotter. A table of point locations was used topeed up the inputting of internal boundaries of a polygon. SYMVU produced a 3-D perspective of SYMAP output while

GRID enabled raster cells to be displayed using the same output techniques as SYMAP and later allowed the multipleverlay of raster calls.

Figure 1.11 An example of a SYMAP output. Note the use of a line printer and over-typing to produce density shades.



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Beginning in the 1970s POLYVRT allowed the conversion between alternate ways of forming area objects.

The ODYSSEY system therefore is the culmination of developments at the Harvard Lab and its purpose was to permit theombination of different sources of data notably using the Dual Integrated Map Encoded (DIME) files from the US Bureauf the Census, Land Use Series data from the US Geological Survey (USGS), World Data Banks I & II of the Central

ntelligence Agency (CIA), LANDSAT data from the National Aeronautical Space Agency (NASA) and soil survey datarom the US Soil Conservation Service. The data were put into a common database and computer programmes usingertain analytical processes of polygon overlay created composite coverages. The results were either coloured or black-

nd-white maps (Lo 1986: 369-87).

GIRAS Geographic Information Retrieval and Analysis System developed by the USGS is oriented to land use and landover maps as a data source. Typically USGS maps are produced on a 1:250,000 and 1:100,000 scale (considered as

medium- to small-scale maps). The system is designed to input, manipulate, analyse and output digital spatial data. Whilewas developed for land use and land cover mapping, in the beginning the developers of the programme werereoccupied by editing and correcting digitizing problems in the land use and associated data base. A vector format wassed in conjunction with a series of linked data files, for example, map files, text files and data files with associated sub-les and rules for data conversions to a standard format were developed. The manipulation and analytical proceduresllowed for nine different transformations including rotation, conversion of geographic coordinates, text and otheronversions, providing summary statistics, interpolation, filtering, generalizations and accuracy estimations. The standard

utput was a coloured or monochrome map, with perspective views, block diagrams and isometric histograms. GIRAS-II isn interactive, on-line, time-sharing, random access input processing system with a powerful database managementystem. However, the major bottleneck in such a system still remained that is, digitizing even with either manual orcanner techniques.

The US Bureau of the Censuss major need was to find a simple method of assigning census returns to correct

eographical locations. Address matching and the use of geographic coordinates proved a major difficulty. DIME filesoded street segments between intersections using identification codes for right and left blocks, identification codes of therom and to nodes (or intersections), x, y-coordinates and address ranges on each side of a street. This file structureorrowed heavily from CGISs arc structure and the common denominator format of POLYVRT. Later on topological ideasf DIME were refined and included in the TIGER model Topologically Integrated Geographic Encoded Reference

System. DIME and TIGER files have been influential in stimulating work on products which relied on street networkatabases:

q vehicle navigation systems (but only if you own a BMW 7-series!)q garbage truck routing (milkos as well)



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q emergency vehicle despatching (police, ambulance, fire).

The production of atlases of computer generated maps for selected variables for selected cities is one application. Simpleomputer maps are now used for marketing and retailing applications and the advent of personal computers (PCs) hastimulated the production of maps using simple mapping packages. All these are now possible because of the digitaloundary files produced by the Census Bureau.

For users of this workbook with access to the Internet you may wish to view copies of DIME and TIGER files at theollowing address:http://www.census.gov/geog.html

ESRI The Environmental Systems Research Institute, founded in 1969, developed the ARC/INFO program which builtn techniques and ideas developed at the Harvard Lab and elsewhere. While initially slow to take hold, by the 1980s

ARC/INFO successfully cornered the GIS market. This was because it was able to implement the CGIS idea of separatettribute and locational information, fused standard relational database management systems (RDBMS) INFO to handlettribute tables with software to handle ARCS a basic design now copied by other systems, and developed a toolbox

which was command-driven and a product-oriented user interface.

ARC/INFO was one of the earliest GISs to take advantage of new super-minicomputer hardware, a platform that wasffordable to many resource management agencies. The emphasis of ARC/INFO has been on independence from specificlatforms and operating systems.

Figure 1.12 Migration path of GIS from large mainframe systems to powerful desktop PC systems.

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Source:After McLaughlin & Coleman 1989.

.2 GIS AND OTHER DISCIPLINES

GIS is said to represent a convergence of technological fields and traditional disciplines. It has been called an enablingechnology because of the potential it offers to the wide variety of disciplines which must deal with spatial data with eacheld providing some technique that make up GIS. While some fields emphasize data collection, GIS emphasized datantegration, modelling and analysis leading some to claim it as the science of spatial information. Apart from geographyhere are several other disciplines which contribute to GIS today. (See Figure 1.13 The relationship between GIS andelected disciplines).

Figure 1.13 The relationship between GIS and selected disciplines

Source:Maguire (1991: 13).

Cartography is concerned with the display of spatial information and the main source of input data for GIS is maps. Theiscipline has a long tradition in the design of maps and recent developments in digital and automated cartographyrovides methods for digital representation and manipulation of cartographic features and methods of visualisation.

Remote sensing of the ground using satellites and aircraft are a major source of geographical data. Many image analysisystems contain sophisticated analytical functions and these data when merged with other data layers are extremelyseful in a GIS.

Photogrammetry is the science of using aerial photographs and techniques for making accurate measurements fromhem. Photogrammetry is the source of most data on topography as ground elevations for input to a GIS.

Surveying provides high quality data on positions of land boundaries, buildings and other land marks.

Geodesy is the source of high levels of positional control and accuracy for GIS. In conjunction with surveying techniquesnd the use of differential global positioning systems (DGPS) accuracies of up to a meter are possible. DGPS use three or



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our of the 24 geo-stationary positional satellites circling the earth to take measurements and through a system ofriangulation produces accurate ground positions.

Statistics provide the theoretical underpinnings of GIS models for analytical, simulation and prediction purposes.Statistics provide insights to understand error and uncertainty in GIS data.

Operations Research provide the tools for optimizing routines for use in GIS especially in decision-making models. Forxample, the quickest route on a network, the optimal location of a hospital and the location of facilities generally call upon

echniques developed in operations research.

Computer Science especially CAD computer aided design, DBMS database management systems, AI artificialntelligence and expert systems all provide GIS with tools and techniques. CAD software, for example, are used for datanput, display and visualisation in 3-D. DBMS contribute methods for representing data in digital form, for systems designnd for handling large volumes of data especially in retrieval and updating records. AI and expert systems use computer

echniques to mimic decisions in such functions as map designs and generalizing map features.

Mathematics, especially geometry and graph theory are used in GIS system design and analysis of spatial data as wells provide the computer functions in mathematical formulas that produce algorithms to solve particular problems.

Civil Engineering especially in transportation and urban design has benefitted from interchange of ideas with GISractitioners.

For reference see: Cowen, D. (1990) What is GIS? in Goodchild & Kemp (eds.) Introduction to GIS, NCGIA CoreCurriculum, Santa Barbara, CA: NCGIA, pp. 1-1 - 1-9).

.3 APPLICATIONS OF GIS

GIS has been used in various ways. Rather than describe these in detail GIS applications may be summarized as follows:

Street network-based

q address matching, finding locations given street addressesq vehicle routing and scheduling, deliveries routing and drive-time studiesq location analysis and site selection, branch location assessment and analysisq development of evacuation movement plans for emergenciesq integrated transport planning

Natural resource-based

q management of wilderness, floodplains, wetlands, forests, agricultural lands, aquifers, wildlifeq Environmental Impact Analysis (EIA), Environmental Auditsq viewshed analysis, intervisibility studiesq hazardous or toxic facility sitingq groundwater modelling and contamination trackingq wildlife habitat analysis, wildlife corridors and migration route planning

Land parcel-based

q land use zoning and subdivision plansq land acquisitionq water quality managementq land ownership management

Facilities management



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q location of underground pipes, cables, sewersq planning facility maintenance, infrastructure planningq tracking energy useq inventory management and lifecycle studiesq base map generationq leak detection, fault location, safety monitoring

Financial services

q demographic profilingq target marketingq insurance claim/risk modelling

Environment

q pollution, weather, climate monitoringq cause-effect studiesq landscape assessmentq conservation planningq

biodiversity libraries

Local Authorities

q planning-building controlq land searchesq boundary change modellingq property road maintenanceq crime analysisq police, fire, ambulance service command and control

Health care

q asset managementq ambulance and emergency mobilisationq epidemiological studiesq road traffic accident analysis, black spots

.4 A CRITIQUE OF GIS

An introduction to GIS as a tool will be incomplete without a discussion of some of its shortcomings and drawbacks. Thisritique should thus begin with what a GIS is not. A GIS is not simply a computer system for making maps even though

he system produces maps at different scales and projections in a variety of visually attractive colours. As an analyticalool a GIS permits the linking and identification of spatial relationships between features in visual form on a computercreen or a paper map. GISs store its information in digital form in a series of linked files in a relational database. Becausef clever computer programming a GIS will be able to retrieve data on particular areas with specific characteristics at willnd show these graphically. In addition, the database management system also links the spatial with other attribute non-raphic non-spatial data to produce meaningful reports and labels for map features.

So a map that we are familiar with, which previously was stored on our shelves and in our desk drawers now is stored as aigital database on a magnetic medium of a floppy disk or hard disk and which is unreadable and unintelligible to theaked eye as a map. Using the database the GIS will be able to add, subtract, multiply and divide the various attributes toroduce new relationships previously unseen and perhaps unthought of. The database concept is central to all good GIS

tructures and this distinguishes it from other simple drafting and computer aided mapping systems which can produceood quality map products but not highlight important relationships or offer any form of analysis. A GIS by sticking to the

undamental questions of what, where and how can also answer the what if? question. Essentially, a GIS provides thebility to link information with a map feature and create new relationships. For example, a GIS may determine theuitability of various sites for development, evaluate environmental impacts, calculate harvest volumes, identify sites for



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ew facilities and so on. (Refer to ESRI 1990 Understanding GIS. The ARC/INFO Method, Redlands, CA: ESRI, pp. 1-1 --10).

That a GIS is a powerful tool cannot be disputed. However, there is the danger though that such a powerful tool whensed improperly could produce nonsense results that can be described variously as spurious correlations or spatialutocorrelations. On example would suffice. Suppose one were recording the incidence of sexually transmitted disease inome remote highland or island location and then simultaneously recorded the number of missionaries at these places. It

may turn out that there is a high degree of association between the two statistics collected when mapped. But it will beangerous to rely on these statistics because there may be no such relationship and the two events may be totally

nrelated. The result was produced by forcing different datasets together and pushing the limits of their use.

GIS is claimed as a new discipline. However, current disciplinary boundaries suggest that this new technology will sitncomfortably in any one or a combination of disciplines. The academic practices and traditions are too entrenched tollow GIS to integrate easily. Thus, GIS will remain a powerful tool for spatial display, analysis and modelling. GIS isredicted to displace cartography, geodesy and other land sciences. The traditional cartographic production process ofaper maps is said to be tedious, expensive, slow to produce and costly to update and maintain. GIS itself is in its infancynd suffers the same kinds of criticisms levelled against traditional cartography. In geodesy, the lack of architectural scaleccuracy even with highly accurate DGPS limits applications at a large-scale. At present even a 1-meter resolution from

DGPS is unsuitable for cadastral mapping and land surveys. These very large-scale cadastres cannot be used becauseGIS are ideally suited to small- to medium-scale work.

n computer science the rage is with object-oriented database systems where objects are self-contained data androgrammes which can help in collecting, manipulating and understanding spatial data. As an example, the Windows-ased graphical user interface (GUI) uses icons(pictures) to depict a file, programme or some application. These can beasily moved about the screen using a pointing device such as a mouse. This application, file or data may be used by theser at will by selecting it to start the program. In simple terms these icons are thus said to be objects. The introduction of

hese ideas into GISs has caused severe anxiety among practitioners and especially among geographers. Manyeographical constructs are implicitly uncertain, for example, the concept of far away. Some spatial objects are often theroduct of interpretation or generalization, for example, proximity, contiguity, randomness, hinterlands, regions and so on.is therefore very difficult to mould the observations around us into the strict and rigidly bounded objects favoured by

omputer programmers and scientists.

A GIS is said to lead to improved spatial analysis. This argument is flawed in two ways. First, there is no way that moreata will lead to better analysis. The idea of an information overload has previously been discussed. Moreover, in theollection-analysis of data there is a large time-lag so that there is always a need to re-evaluate, re-define and adapt tohanges recorded and observed. This continual distillation and refinement process is an essential part of the scientific

method rather than the static, slice-of-time analysis of the collected data. Secondly, as with traditional methods, GISs canreoccupy the practitioner with the mechanics and technical aspects of the technology that much more time is spenteveloping the model and tools than the analysis itself. This is a distinct possibility with novice users of GISs. With morexpert users the problems with data availability, non-availability, of the right kind, in the right form, as well as theuantity and quality of the hardware are some of the on-going issues to be resolved.

GISs are not easy to use, not only because of the technology but also because of the lack of an industry standard. With so

many different vendors of GIS products there is a lack of a common interface for all users. There is need, on the oneand, to know the command structure of a particular program. For example, the widely used PC ARC/INFO has about,600 different commands which a user may need to be aware of if that user wishes to be fully conversant with theystem. On the other hand, a user needs to have a broad understanding of the theory and mechanics of spatial analysis.

Thus, to be able to use a GIS as a simple do-all tool is a false assumption. There certainly much more to it than simplyroducing a map as an end-product it may make a pretty picture but it may not withstand minute and critical scrutiny.

The recent advent of a Windows-based version of ARC/INFO may provide the much needed standard because all vendorswould have to write their programmes so that they are compliant with the requirements of Windows programming.

Current GISs are deficient in handling temporal data either to show changes or trends. No models exist to show spatialuccession, for example, changing land uses in different locations. The ability to model change through time is constrained

y the lack of suitable data and the technology itself to show changes is still unsophisticated.

Organisational issues in the implementation of GIS has seldom been discussed in the literature. This is new andxpensive technology which requires someone in the organisation to promote, develop and nurture. There is limitedcceptance and effective use of GIS by government agencies because of the high cost of implementation, difficulty of



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raining and keeping personnel and fear of organisational change. The latter is a structural problem because people in theigher levels of administration may not wish to abdicate their decision-making roles, while those using GIS at the coal-

ace may wish to implement certain decisions suggested by the GIS but which do not filer upwards to those who actuallymake the decisions. These hierarchical decision-making structures may make it difficult for the widespread adoption ofGISs. Moreover, there is limited documentation of successful GIS implementation to convince the decision-maker to investn this new technology. (See Aangeenbrug, R.T. 1991. A critique of GIS in Maguire, Goodchild & Rhind (eds.) pp. 101-07).

.5. ANOTHER QUICK QUIZ

1. Examine the symap printout carefully (Figure 1.11). What are the advantages and limitations of thiskind of a mapping system? How are irregularly shaped areas shown? What about drawing linefeatures on such a system. Can point locations also be shown using this mapping package?

2. Explain the difference Automated Mappin/Facilities Management (AM/FM), Computer Aided Design(CAD) and GIS.

3. Explain the difference between attribute data and cartographic data. Give examples


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3. GIS: NUTS AND BOLTS

3.1 BASIC ELEMENTS

There appear to be four elements which together comprise a GIS computerhardware, computer software, data and liveware.

a. The computer hardware can range from the most sophisticated mainframecomputer to mini-computers, high performance workstations to personalcomputers. The trend in the late 1990s is towards workstations using the UNIX

operating system. Included under hardware are input and output devices. Inputdevices include digitizers, scanners and other automated digital data captureequipment. For data output, apart from the computer monitor and the printer,there are plotters of various kinds as well as output direct into magnetic devicessuch as floppy disks, cartridges and more recently CD-ROMs (compact disks-read only memory).

b. GIS computer software has been developed to very sophisticated levels toinclude a large number of commands and a variety of functionality. Three basicGIS designs have evolved. These are called file processing, hybrid and

extended designs. In the file processingdesign, each data set and function isstored as a separate file and these are linked together during analyticaloperations. Examples of systems using this design are IDRISI, IMAP, E-RMS,SAGE. In the hybrid designattribute data are stored separately in a DBMSwhile geographical data are stored and processed by a different computerprogramme. ARC/INFO, MapInfo, GenaSys are examples of hybrid designs. Inthe third design, extended DBMSboth the geographical and attribute data arestored in a DBMS which is extended to provide appropriate geographicalanalytical functions. The best known examples using the extended design areSYSTEM 9 which extends the EMPRESS DMBS and TIGRIS systems.

c. GIS Data. The third important element in a GIS are the data. Geographicaldata are very expensive to collect, store and manipulate because huge volumesare required even for small areas. It has been estimated that the cost of data isoften more than twice the cost of the software and hardware in a GIS. Data ofthe right form and type has always been very scarce even with the use ofremote sensing satellites and mapping programmes to collect digital data on anational scale.

d. Liveware. This is the most significant GIS element because people are

responsible for designing, implementing and using GIS. The lack of trainedpersonnel has impeded the more widespread implementation of GIS. The focuson the technology has sometimes overlooked the more important element of theGIS the people who provide the intelligence to interpret and use the results

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that GISs produce.

3.2 GIS VIEWPOINTS

GIS can be synthesized and presented in the form of three distinct butoverlapping viewpoints. These are termed the map, database and spatial

analysis viewpoints.

a. Map view. This focuses on the cartographic aspects of the GIS. In thisschool of thought, the GIS is seen as a map processing or display system. Eachmap is conceived of as a layer, theme or coverage which are overlayed in orderto search for patterns. The search for patterns or manipulation includesfunctions that allow common features to be added or unique features to besubtracted from the map to produce a new map as a result of the search. Suchideas have extensive applications especially when the data are in the form ofremotely sensed images. Many topographic and thematic mapping agencies

favour this map view and rely on a GIS to produce high quality maps and chartsfor public consumption.

b. Database view. This view of a GIS emphasizes the importance of a DBMS.A sophisticated DBMS is integral to many GISs and is favoured by users with acomputer-information science background. From the various applications of aGIS, especially those which record transactions, those that require frequent useof simple queries such as land registration and those requiring high volumes oftransactions such as real-time vehicle positioning systems and the like, a GISusing a database approach is most obvious.

c. Spatial analytic view. This view focuses on the analytical and modellingaspects of the technology and is conceived by some as a spatial informationscience. Users also accept that this function of a GIS separates it from otherkinds of information systems.

These views need not necessarily be taken singly since, depending on theapplication at hand, all three may be included. The views may be thought as aset of interlocking chains, with each view being emphasized in particularapplication and software programmes. This also serves to highlight the

numerous uses of GISs, its generality in application and the heterogeneity ofthe GIS community. (See Maguire, D.J. (1991) An overview and definition ofGIS in Maguire, Goodchild & Rhind (eds.) pp. 9 - 10).

3.3 GIS: BASIC QUESTIONS

The basic questions which a GIS can answer may be classified in a genericfashion. There are six generic questions that a sophisticated GIS can address:

Modelling

Location What is at ...? For example,the number of animals in ahabitat.



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Condition Where is it? Find a locationwhere certain conditions aresatisfied. This is theintersection of two pieces ofdata

Routing Which is the best way to ...?Calculates the best, fastest,shortest, most scenic route

or the route between twoplaces.

Trends What has changed since ...?Monitoring change over time,for example, deforestation

Patterns What spatial patterns exist?Identification of patterns helpdescribe and comparedistributions of aphenomena, to understand

the processes and accountfor their distribution.

What if? To determine what happens when one changes some feature orvariable. Requires geographic and other information and possibly scientificlaws, for example, sea level changes, global warming, desertification for an

explanation.

3.4 REQUIREMENTS OF A GIS

Smith et al. (1987) discuss what should be required of a GIS. A GIS should:

q be able to work with large, heterogenous spatial databases;q be able to query the database about the existence, location and

characteristics of a wide variety of objects;q operate efficiently, so that the user can work interactively with the

underlying data and the required data analysis models;q be easy to tailor to a variety of applications, as well as to many kinds of

users;q be able to learn in significant ways about the data and the users

objectives; and,q be able to supply a readily interpretable output product for the ultimate

users of the system.

The requirements present a rich list of research projects which will appeal to anumber of research disciplines. It caters both for pure researchers as well as forthe practitioners and ultimately those users of the results of GIS analysis. (SeeSmith et al. (1987).



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Summary

GIS is of enormous commercial significance and is having an important impactin the private, public and commercial world. GISs have been used tounderstand and to provide solutions to key socio-economic and environmentalproblems. Many people and groups use GIS for a very wide variety ofapplications. Inevitably, different people have different ideas of what a GIS isand what it may be used for. In summary terms a GIS is an integrated collectionof computer hardware, software, data and liveware that operates in aninstitutional context. GIS is a special case of an information system sharingmany common features with other systems. The focus on spatial analyticalmodelling distinguishes GISs from other systems. Spatial searching and overlayoperations are fundamental functional features of any GIS.

FURTHER READING

Aageenbrug, R.T.(1991) A critique of GIS in Maguire, Goodchild & Rhind(eds.) Ch. 8, pp. 101 - 107.

Abler, R., Adams, J.S. & Gould, P. (1971) Spatial Organization: TheGeographers View of the World. London: Prentice Hall.

Cowen, D. (1990) What is GIS? in Goodchild, M.F. & Kemp, K (eds.), pp. 1-3 -

1-9.

Dangermond, J. (1990) A classification of software components commonlyused in geographic information systems in Peuquet, D. F. & Marble, D. F.(eds.) pp. 30 - 51.

Environmental Systems Research Institute (ESRI) (1990) Understanding GIS:The ARC/INFO Method. Redlands CA: ESRI.

Garson, G.D. (1971) Handbook of Political Science Methods. Boston, MA:Holbrook Press Inc. pp. 49 - 65.

Goodchild, M.F. & Kemp, K. (eds.) (1990) Introduction to GIS, NCGIA CoreCurriculum, Santa Barbara, CA: NCGIA.

Lo, C.P. 1(986) Applied Remote Sensing, Harlow: Longman, Ch. 9 GeographicInformation Systems, pp. 369 - 387.

Lord Chorley (1987) Handling Geographic Information. Report of the Committee

of Enquiry chaired by Lord Chorley, London: HMSO.

Maguire, D.F. (1991) An overview and definition of GIS in Maguire, Goodchild& Rhind (eds.), Ch. 1, pp. 9 - 20.



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Maguire, D.F., Goodchild, M.F. & Rhind, D. (1991) (eds.) GeographicalInforamtion Systems, London: Longman Scientific & Technical.

Marble, D.F. (1984) Geographic information systems: An Overview, PECORA9 Proceedings, Spatial Information Technologies for Remote Sensing Todayand Tomorrow, Oct. 2-4, Sioux Falls, SD: IEEE, pp. 18-24.

Rhind, D.W. (1981) Geographical Information Systems in Britain, in Bennett,R.J. & Wrigley, N. (eds.) Quantitative Geography: Retrospect and prospect,London: Routledge & Kegan Paul, pp. 17 - 35.

Smith, T.R., Menon, S., Star, J.L. & Estes, J.E. (1987) Requirements andprinciples for the implementation and construction of large-scale geographicinformation systems, International Journal of GIS, v.1(1) pp. 13-32.)

Tomlinson, R.F. (ed.) (1972) Geographic Data Handling, Commission on

Geographical Data Sensing and Processing. Ottawa: International GeographicalUnion.

REVISION

1. How are data associated with geography in a GIS?2. Explain the difference between a transaction-based information system

and a data-based information system. What are the advantages anddisadvantages of each?

3. Compare GIS to an airline reservation system. How do the informationsystem definitions presented in this module apply to the airlinereservation example?

4. Describe how crime data can be used at the operations, managementand policy levels of local government.

5. The pattern of GIS development since 1965 has been largelyattributable to the changing balance between the costs of hardware,communications and software development. Discuss.

WORKING WITH PCs

This guide has been prepared to enable you to start using microcomputers onthe Faculty of Applied Science Local Area Network (LAN). It describes only theessential and most commonly used commands and their parameters. Thenetwork software is Novell Netware and operates 24 hours a day.

Disk Drives. Microcomputers usually have two floppy disk drives and a harddisk. These are labelled A:, B: and C: respectively. The disk drives will format,write and read diskettes to any density format: 360 K, 720 K, 1.2 Mb. Neverremove your floppy disk when the drive light is on. Drive G:\SCRATCH is a



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scratch disk space where users can temporarily put large files they are workingon, but be aware that files on this drive are routinely deleted without warning asthe available disk space fills up.

Backup. Get into the habit of backing up your work on floppy disks frequentlyand as often as convenient. The consequences of wasted effort, lost work ordamaged work can be very time consuming and frustrating.

Logging On. You may log on to the network by typing RSTUDENT on thescreen showing the University of Canberra logo. Remember to log off when youfinish by typing BYE.

Common CommandsAll commands that you type into the computer are shown in courier font.

format a: will format your diskette if you have not already done so. You do thisonce only for new disks. Formatting a used disk will wipe out all data on it.

CD \TIGER will change your directory to a different path, here its path ischanged to TIGER which is the name of a directory on the current drive.

DIR will give you a list of files in your current directory.DIR /W will give you a directory listed to the width of your screenDIR /P will give you a directory listed a page at a timeMD NEWMAN will create a new directory called NEWMAN.RD NEWMAN will remove a directory called NEWMAN.

COPY A:RAILROAD B:RAILROAD will copy a file called RAILROAD from the A:drive to the B: drive. Make sure

there are floppy disks in both these drives.

DELETE A:RAILROAD will delete a file called RAILROAD on the floppy disk inthe A: drive.RENAME A:RAILROAD.DOC A:RAILWAY.DOC will rename a file calledRAILROAD.DOC to a file called RAILWAY.DOC in the A: drive.

BYE will log you out of the network.

Filenames. Filenames consist of from 1 to 8 characters, a decimal point and anoptional 3 character extension. The legal characters include A-Z, 0-9 $ & # ! %_ [ ]. For example, HAPPY.DOC or just HAPPY are valid filenames.

No spaces may appear in the filename and case is irrelevant in filenames, as itis for all DOS commands. (DOS stands for disk operating system.)The wildcard characters are

? for any single character, and * for any character or combination of characters.Therefore B:*.* refers to all files on B: drive, whilst B:*.doc refers to all files withthe .doc extension.



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Note that the following names cannot be used as filenames: AUX, COM1,COM2, CON, LST, PRN, LPT, NUL. These refer to DOS devices.

GIS Net Sites

For students who have access to the Internet the following address gives you abookmark belonging to Jim Aylward ([email protected]) who has personallycompiled a massive list of GIS net sites as at 1 July 1995. You are invited tosurf the Net using this list. The list is a dynamic one and is being added tocontinually. This is just a starting point. Have a go, the internet address is:

Citation

To reference this material the correct citation for this page is as follows:

Cho, G (1995) Geographic Information Systems. Students Manual. Module 1.Canberra: University of Canberra and CAUT; http://infosys-

law.canberra.e

Documents

Gis Manual Self Learning