gis primer

8/12/2019 GIS Primer

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FRONT PIECE

David J. BuckleyCorporate GIS Solution !ana"erPaci#ic !eridian Reource$ Inc.

The GIS Primer provides an overview of issues and requirements forimplementing and applying geographic information systems technology.This primer focuses on practical issues concerned with the responsible

implementation and application of GIS technology. The primer is directed forthose with limited exposure to GIS. It is intended purely as in introductory textwith an emphasis on identifying and clearly illustrating fundamental concepts inGIS applications.

PREF%CE

This workbook is a result of several years experience in applying geographicinformation systems GIS! technology to typical forestry" natural resourcemanagement" and environmental problems. #any of the terms and conceptsintroduced in this book have been compiled from a variety of different sources.These include some of the prevalent text books in the field" but most have beenfirmly implanted from practical experience. GIS is in essence" an applied science.


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The more hands-onyou have the more entrenched the methodologies andtechniques become for effectively applying the technology.

The sample applications presented in the GIS Primer have been compiled frommy experiences representing real operational requirements of selected IGIS

clients" past and present. These sources include provincial and federal naturalresource agencies in $anada and the %nited States" and private forestrycompanies across &orth 'merica. The models and(or formulas used in thesample applications have been simplified in an effort to focus on procedures andtechniques for applying GIS. The sample applications are presented to providesimple operational examples of fundamental GIS analysis techniques.

'nnual updates are undertaken to this book to reflect the dynamic nature of thecommercial GIS marketplace" and to reflect my understanding of what GIS reallyis. The ever increasing rate of technological change prompts me to update thePrimer to reflect the new and exciting capabilities that GIS technology provides.

)or the novice reader" don*t be overwhelmed with this change. GIS has changedso drastically since this book was originally written in +,-- but in so many waysremains the same. $hanging technology has provided many more capabilitiesand possibilities" often beyond the comprehension of the average user.&onetheless" ultimately the tool is only as good as the craftsman using it.$onsistently it is the imagination and creativity of the domain specialistusing GISthat makes GIS work" not the new technological capabilities or increasedperformance. I believe that while the GIS vendor community" hardware andsoftware vendors alike" provide us with newer" better and faster technologicaltools" it is in the end" the domain specialists applying the tool that define state-of-the-art. The heartbeat of GIS still lies in the field and district offices" the logging

divisions" the engineering offices" and with the small GIS entrepreneurs in officeseverywhere.

#any thanks to my colleagues" past and present" who have supported me andworked with me over the years. This workbook reflects our collective experiencesand knowledge. ' special thanks to my partners at IGIS who share a commonvision of the role of GIS in today*s society. 'nd lastly" to /oe 0erry" my GISpartner in crime" who continues to ama1e me with his insight and genuine lovefor all things GISsy. #any of the figures and diagrams in the Primer aregraciously provided by /oe from his gCON Softwareset. #any thanks for all yoursupport.

The GIS Primer is provided by Innovative GIS Solutions, Inc.as the workbookand reference document for all our introductory GIS education workshops. Ifyou*d like more copies please give us a call.

David J. Buckley


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Fort Collin$ ColoradoFe&ruary '(()

e2mail3 dbuckley4 pacificmeridian.com

P*RPOSE

T+e purpoe o# t+i &ook i to provide an overvie, o# t+e iue andre-uireent #or ipleentin" and applyin" "eo"rap+ic in#orationyte tec+nolo"y.

The book is intended to provide resource specialists and managers with anexposure to GIS technology and terminology" so that papers" applications" andexhibits on GIS will be more understandable and useful in the future. This bookpresents a substantial amount of GIS theory" and a whole bunch of bu11words"but is also supplemented with relevant forestry based applications to illustrate theconcepts and techniques for applying GIS technology.

T+e #ocu o# t+i &ook i on practical iue concerned ,it+ t+eipleentation and application o# GIS tec+nolo"y. T+i &ook i directed att+e reource pecialit and/or ana"er ,+o +a +ad liited e0poure toGIS. It i intended purely a an introductory te0t ,it+ an ep+ai on

identi#yin" and clearly illutratin" priitive concept in "eo"rap+icin#oration yte application.

5opefully" with this approach in mind the confusion and mystique that oftensurrounds GIS can be clarified" resulting in an understandable framework for thesuccessful evaluation" implementation" and application of GIS technology.
mailto:[email protected]:[email protected]


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This book is based purely on practical experience of the author and in no wayshould be construed as a comprehensive statement on GIS. 6eferences areprovided at the back of the book for further reading and detail.

Important points or quotes are identified throughout the book by &oldtext. Italics

are used throughout the text to identify technical terms that imply somethingother that their conventional meaning.

'ny comments or suggestions on the content or format of this book are welcome.Please send any comments to 7buck4innovativegis.com7.

8n9oy :

%BO*T T1E %*T1OR

Bio"rap+ical Sketc+

David J. Buckley

$orporate GIS Solutions #anagerPacific #eridian 6esources" Inc.

David Buckley is the Corporate GIS Soluions Manager for Pacific Meridian Resources,

Inc. PMR!, a fir" dedicated to providing responsi#le GIS i"ple"entation and

application solutions for a $ide range of land related "anage"ent disciplines.Mr. Buckley is considered a leading GIS i"ple"entation and application consultant

throughout %orth &"erica consulting to govern"ent agencies, hard$are vendors,

soft$are vendors, and private industry. Mr. Buckley is $ell versed in the issues critical to

proper GIS i"ple"entation and responsi#le application develop"ent. 'is seniorconsulting e(perience provides the necessary #ackground and a#ility to understand and

act upon the #usiness re)uire"ents of an organi*ation, and to place infor"ation syste"s

and resources in their appropriate conte(t $ith respect to the goals and o#+ectives of thoseorgani*ations. Specifically, Mr. Buckley has several years e(perience applying GIS
mailto:[email protected]:[email protected]


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technology to operational forest "anage"ent issues and pro#le"s $ithin govern"ent and

the private sector in Canada and the nited States.

Mr. Buckley has "anaged and participated in pro+ects that focus on integrating custo"

"odeling do"ain re)uire"ents utili*ing GIS technologies. Specific e(a"ples include

integrated resource planning, forest inventory "anage"ent, forest fire "odeling,environ"ental i"pact assess"ents, ecosyste" si"ulation "odeling, at"ospheric

dispersion "odeling, a"ong others. In his role as the principal GIS consultant at IGIS he

has developed significant e(pertise focused on the integration and application ofco""ercial GIS soft$are platfor"s into operational $orking environ"ents.

Mr. Buckley has also conducted nu"erous $orkshops and se"inars on GIS technology

for #oth pu#lic and private sector audiences. -his has included the pu#lication of an

introduction to GIS #ook entitled -he GIS Pri"er. Mr. Buckley is a fre)uent presenter atGIS conferences and sy"posiu"s throughout %orth &"erica. 'e has nu"erous

pu#lications in industry +ournals focusing on the successful and cost effective application

of GIS technologies.

David J. Buckley$E2ail3 d#uckleypacific"eridian.co"

Pacific Meridian Solutions, Inc. Suite /00, 1000 South College &ve.

2ort Collins, C3 40515

-elephone6 780! 970 : 5700

2&; 6 780! 970 < 1/00

=e# Site6 $$$.innovativegis.co"

C1%PTER '3 T1E N%T*RE OF GEOGR%P1IC INFOR!%TION

This chapter reviews the asic fundamentals of geographic data and

information. The focus is on understanding the asic structure ofgeographic data, and how issues of accuracy, error, and !uality are

paramount to properly using GIS technology. The estalishment of aroust dataase is the cornerstone of a successful GIS.
mailto:[email protected]://www.innovativegis.com/mailto:[email protected]://www.innovativegis.com/


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Maps and Spatial Infor"ation

Characteri*ing Geographic 2eatures

Spatial Data &ccuracy and >uality

!%PS %ND SP%TI%4 INFOR!%TION

The main method of identifying and representing the location of geographicfeatures on the landscape is a ap. ' map is a graphic representation of wherefeatures are" explicitly and relative to one another. ' map is composed ofdifferent geographic features represented as either points" lines" and(or areas.8ach feature is defined both by its location in space with reference to acoordinate system!" and by its characteristics typically referred to as attributes!.;uite simply" a map is a model of the real world.

The ap le"endis the key linking the attributes to the geographic features.'ttributes" e.g. such as the species for a forest stand" are typically representedgraphically by use of different symbology and(or color. )or GIS" attributes need tobe coded in a form in which they can be used for data analysis 0urrough" +,-


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The coordinate system may be of a variety of types. )or natural resourceapplications the most common are3

"eo"rap+ic coordinatesuch as latitude and longitude" e.g. >


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#aps are the traditional method of storing and displaying geographic information.

% ap portray 6 kind o# in#oration a&out "eo"rap+ic #eature. T+e3

Hocation and extent of the feature

'ttributes characteristics! of the feature6elationship of the feature to other features.

Geography has often been described as the study of ,+y ,+at i ,+ere. Thisdescription is quite appropriate when considering the three kinds of informationthat are portrayed by the traditional map

the location and e0tentof a feature is identified explicitly by reference toa coordinate system representing the earth=s surface. This is ,+erea

feature is.the attri&uteof a feature describe or characteri1e the feature. This is,+atthe feature is.The relationship of a feature to other features is implied from the locationand attributes of all features. 6elationships can be defined explicitly" e.g.roads connecting towns" regions ad9acent to one another" or implicitly"e.g. close to" far from" similar to" etc. Implicit relationships are interpretedaccording to the knowledge that we have about the natural world.6elationships are described as +o,or ,+ya feature is.

The geographic information system distinguishes between the spatialandattriuteaspect of geographic features.

The identification of relationships between features" within a common theme oracross different themes" is the primary function of a GIS.

C1%R%CTERI7ING GEOGR%P1IC FE%T*RES

'll geographic features on the earth=s surface can be characteri1ed and definedas one of three basic feature types. These are point$ line$ and area.

Pointdata exists when a feature is associated with a single location in


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space. 8xamples of point features include a fire lookout tower" an oil wellor gas activity site" and a weather station.4ineardata exists when a feature=s location is described by a string ofspatial coordinates. 8xamples of linear data include rivers" roads"pipelines" etc.

%realdata exists when a feature is described by a closed string of spatialcoordinates. 'n area feature is commonly referred to as a poly"on.Polygonal data is the most common type of data in natural resourceapplications. 8xamples of polygonal data include forest stands" soilclassification areas" administrative boundaries" and climate 1ones. #ostpolygon data is considered to be homogeneous in nature and thus isconsistent throughout.

8very geograpic phenomenon can in principle be represented by either a point"line" and(or an area.

GIS ata Structures illustrating the difference between Jector and 6aster formats 'dapted from0erry!

$ommonly" an identifieraccompanies all types of geographic features. Thisdescription or identifier is referred to as a la&el. Habels distinguish geographicfeatures of the same type" e.g. forest stands" from one another. Habels can be inthe form of a name" e.g. 7Hake Houise7" a description" e.g. 78HH7 or a uniquenumber" e.g. 7+@D7. )orest stand numbers are examples of polygon labels. 8achlabel is unique and provides the mechanism for linking the feature to a set ofdescriptive characteristics" referred to as attribute data.


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It is important to note that geographic features and the symbology used torepresent them" e.g. point" line" or polygon" are dependant on the graphic scalemap scale! of the data. Some features can be represented by point symbologyat a small scale" e.g. villages on a +3+"CCC"CCC map" and by areal symbology at alarger scale" e.g. villages on a +3+C "CCC map. 'ccordingly" the accuracy of the

feature=s location is often fu##ierat a smaller scale than a larger scale. Thegenerali1ation of features is an inherent characteristic of data presented at asmaller scale.

ata can always be generali1ed to a smaller scale" but detail $'&&KT becreated :

6emember" as the scale of a map increases" e.g. +3+>"CCC to +3+CC"CCC" therelative si1e of the features decreaeand the following may occur3

Some features may disappear" e.g. features such as ponds" hamlets" andlakes" become indistinguishable as a feature and are eliminated.)eatures change from areas to lines or to points" e.g. a village or townrepresented by a polygon at +3+>"CCC may change to point symbology at

a +3+CC"CCC scale.)eatures change in shape" e.g. boundaries become less detailed andmore generali1ed. andSome features may appear" e.g. features such as climate 1ones may beindistinguishable at a large scale +3+>"CCC! but the full extent of the 1onebecomes evident at a smaller scale +3+"CCC"CCC!.

'ccordingly" the use of data from vastly different scales will result in manyinconsistencies between the number of features and their type.

The use and comparison of geographic data from vastly different source scales istotally inappropriate and can lead to significant error in geographic dataprocessing.


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D%T% %CC*R%C8 %ND 9*%4IT8

The quality of data sources for GIS processing is becoming an ever increasingconcern among GIS application specialists. ith the influx of GIS software on the

commercial market and the accelerating application of GIS technology toproblem solving and decision making roles" the quality and reliability of GISproducts is coming under closer scrutiny. #uch concern has been raised as tothe relative error that may be inherent in GIS processing methodologies. hileresearch is ongoing" and no finite standards have yet been adopted in thecommercial GIS marketplace" several practical recommendations have beenidentified which help to locate possible error sources" and define the quality ofdata. The following review of data quality focuses on three distinct components"data accuracy" quality" and error.

%ccuracy

The fundamental issue with respect to data is accuracy. %ccuracy i t+ecloene o# reult o# o&ervation to t+e true value or value accepteda &ein" true. This implies that observations of most spatial phenomena areusually only considered to estimates of the true value. The difference betweenobserved and true or accepted as being true! values indicates the accuracy ofthe observations.


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0asically two types of accuracy exist. These are poitionaland attri&uteaccuracy. Poitional accuracyis the expected deviance in the geographiclocation of an ob9ect from its true ground position. This is what we commonlythink of when the term accuracy is discussed. There are two components topositional accuracy. These are relativeand asolute accuracy.$solute

accuracyconcerns the accuracy of data elements with respect to a coordinatescheme" e.g. %T#. %elative accuracyconcerns the positioning of map featuresrelative to one another.

Kften relative accuracy is of greater concern than absolute accuracy. )orexample" most GIS users can live with the fact that their survey townshipcoordinates do not coincide exactly with the survey fabric" however" the absenceof one or two parcels from a tax map can have immediate and costlyconsequences.

%ttri&ute accuracyis equally as important as positional accuracy. It also reflects

estimates of the truth. Interpreting and depicting boundaries and characteristicsfor forest stands or soil polygons can be exceedingly difficult and sub9ective.#ost resource specialists will attest to this fact. 'ccordingly" the degree ofhomogeneity found within such mapped boundaries is not nearly as high inreality as it would appear to be on most maps.

9uality

9uality can iply &e de#ined a t+e #itne #or ue #or a peci#ic data et .ata that is appropriate for use with one application may not be fit for use withanother. It is fully dependant on the scale" accuracy" and extent of the data set"

as well as the quality of other data sets to be used. The recent %.S. Spatial ataTransfer Standard STS! identifies five components to data quality definitions.These are 3

HineagePositional 'ccuracy

'ttribute 'ccuracyHogical $onsistency$ompleteness

4inea"e

The lineage of data is concerned with historical and compilation aspects of thedata such as the3

source of the datacontent of the datadata capture specifications


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geographic coverage of the datacompilation method of the data" e.g. digiti1ing versus scannedransformation methods applied to the data andthe use of an pertinent algorithms during compilation" e.g. linearsimplification" feature generali1ation.

Poitional %ccuracy

The identification of positional accuracy is important. This includes considerationof inherent error source error! and operational error introduced error!. ' moredetailed review is provided in the next section.

%ttri&ute %ccuracy

$onsideration of the accuracy of attributes also helps to define the quality of thedata. This quality component concerns the identification of the reliability" or level

of purity homogeneity!" in a data set.

4o"ical Conitency

This component is concerned with determining the faithfulness of the datastructure for a data set. This typically involves spatial data inconsistencies suchas incorrect line intersections" duplicate lines or boundaries" or gaps in lines.These are referred to as spatial or topological errors.

Copletene

The final quality component involves a statement about the completeness of thedata set. This includes consideration of holesin the data" unclassified areas" andany compilation procedures that may have caused data to be eliminated.

The ease with which geographic data in a GIS can be used at any scalehighlights the importance of detailed data quality information. 'lthough a data setmay not have a specific scale once it is loaded into the GIS database" it wasproduced with levels of accuracy and resolution that make it appropriate for useonly at certain scales" and in combination with data of similar scales.

ErrorTwo sources of error" in+erent and operational" contribute to the reduction inquality of the products that are generated by geographic information systems.In+erent erroris the error present in source documents and data. Operationalerroris the amount of error produced through the data capture and manipulationfunctions of a GIS. Possible sources of operational errors include3


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@C metres in either direction from the identified position of the feature on themap. $onsidering that the use of GIS commonly involves the integration ofseveral data sets" usually at different scales and quality" one can easily see howerrors can be propagated during processing.

E0aple o# area o# uncertainty #or overlayin" data

Several comments and "uideline on t+e reco"nition and aeent o#errorin GIS processing have been promoted in papers on the sub9ect. These aresummari1ed below3

There is a need for developing error statements for data contained within

geographic information systems Jitek et al" +,-B!.The integration of data from different sources and in different originalformats e.g. points" lines" and areas!" at different original scales" andpossessing inherent errors can yield a product of questionable accuracyJitek et al" +,-B!.The accuracy of a GIS2derived product is dependent on characteristicsinherent in the source products" and on user requirements" such as scaleof the desired output products and the method and resolution of dataencoding #arble" Peuquet" +,-D!.The highest accuracy of any GIS output product can only be as accurateas the least accurate data theme of information involved in the analysis

&ewcomer" S1a9gin" +,-B!.'ccuracy of the data decreases as spatial resolution becomes morecoarse alsh et al" +,-A!. and

's the number of layers in an analysis increases" the number of possibleopportunities for error increases &ewcomer" S1a9gin" +,-B!.

C1%PTER :3 T1E N%T*RE OF GEOGR%P1IC INFOR!%TION

This chapter reviews the structural components and design of GISdata models. The focus is on reviewing spatial and attriute datamodels, and how data is encoded y the GIS software. This chapterdescries GIS technical components and will e of most interest totechnical staff and GIS operators.
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=hat is a GIS ?

Co"ponents of a GISGIS Data Models

Spatial Data Relationships

;1%T IS % GIS

gis primer

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