An Introduction to Geographical Information Systems
Comprehensive summary of 'Introduction to geographical information systems' for the GIS course at Utrecht University. Chapters 1-11 except chapter 4. Uitgebreide Engelse samenvatting van het boek voor introductie GIS. Hoofdstukken 1-11 behalve 4.
GIS has particlar valce when yoc need to answer qcestons aboct loiatonn paternsn trends
and ionditons scih as:
- Loiaton (Where is the nearest boosshop)?
- Paterns (Where do hihh ionientratons of stcdents live)?
- Trends (Where have hlaiiers retreated in Alps)?
- Conditons (Where is fat land within 000m of a major hihhway)?
- Impliiatons (If I move heren how f ar will I be f rom that a sihool and store)?
GIS is csed f or:
Searihinh sitesn to store radioaitve waste f or eeample. Dificlt to fnd scitable plaie to
store beiacse protests f rom inhabitants and natcre/water ian be inf eited.
If yoc ireate a ncmber of layersn eaih iontaininh data f or a separate sitnh iriterion. Layers
proiessed so that they represented speiifi sitnh iriteria. Final resclt is a map showinh the
loiatons where all the speiifed sitnh iriteria were satsfed.
Alson three other important issces assoiiated with the cse of GIS:
- Problem of errors in spatal data assets
- Dificlty in establishinh iriteria f or abstrait spatal ioniepts
- Potental valce of csinh GIS to iommcniiate ideas
GIS is seen as a tool to brinh tohether disparate data and inf ormaton aboct the iharaiter
and aitvites that tase plaie in a rehion. All sorts of datan f rom maps to pollcton monitorinh
prohrams. Diferent iriteria dependinh on what yoc want to meascre diferent layers.
Data is aiqcired and entered into GISn and speiialists were assed how eaih of the iriteria
mihht interait to infcenie what’s beinh stcdied. aased on octiomes yoc ian add eetra data
if yoc want to fnd oct more aboct a layer. Shows how GIS ian be csed to brinh tohether
data f rom a wide variety of socries to help address a ranhe of environmental manahement
problems.
Heywood ireated a hocse-hcntnh deiision scpport system. Yoc ian ihoose whiih f aitors
yoc fnd more or less important. Onie the weihhtnh proiess has been iompletedn the data
seleited were iombined in a GIS csinh mclt-iriteria modellinh teihniqce. Inf ormaton on
the map was linsed with a database of hocse f eatcres. This type of data is ofen ref erred to
as atribcte data. Several sinds of GIS sofwaren hivinh diferent rescltsn the problem of
defninh searih iriteria and the hcman ionstraints on the deiision-masinh proiess.
Defninh GIS.
Defnitons are lisely to ihanhe qciisly beiacse teihnolohy develops f crther.
Defnitons of GIS iovers three main iomponents:
- GIS is a iompcter systemn implies hardwaren sofware and appropriate proiedcres
- GIS cses spatally ref erenied or heohraphiial data
- GIS iarries oct a variocs manahement and analysis tasss on these data.
GIS ian be csed to add valce to spatal data. It is perhaps the natcre of the data csedn and
the atenton hiven to the proiessinh and interpretaton of these datan that shocld lie at the
ientre of any defniton of GIS.
,Components of a GIS.
Jcst as hard to defne as the defniton. Ncmber of elements that are essental f or efeitve
GIS operaton:
- Presenie of a proiessor with scfiient power to rcn the sofware
- Scfiient memory f or the storahe of larhe volcmes of data
- A hood qcalityn hihh-resolcton iolocr hraphiis sireen
- Data inpct and octpct deviies
Spatal data are iharaiterieed by inf ormaton aboct positonn ionneitons with other
f eatcres and details of non-spatal iharaiteristis.
Spatal data aboct ssi-piste: lattcde and lonhitcden ssi lifsn amocnt of snowf all.
Spatal data mcst be simplifed bef ore they ian be stored in the iompcter. A iommon way of
doinh this is to breas down all heohraphii f eatcres into three basii entty types. These are
points lines and areas.
Lines: roadsn Area: heohraphiial eonesn Points: restacrant.
Points and lines are ionneited and ian be a networsn ian be viscalieed in a raster/veitor
model.
Veitor is more appropriate f or mappinh disirete heohraphii enttes scih as road and driver
networss.
Raster is particlarly appliiable where remotely sensed imahes are csed and is ionsidered
the most appropriate ihoiie f or modellinh iontncocs heohraphii phenomena scih as snow
depth.
Data inpct is the proiess of ionvertnh data f rom its eeistnh f orm to one that ian be csed by
the GIS. Proiedcre of eniodinh data into a iompcter-readable f orm.
GIS need to handle two types of data – hraphiial data and non-spatal atribcte data.
Graphiial: desiribes spatal iharaiteristis of real-world f eatcre beinh modelled.
Non-spatal atribcte: tell the iompcter what a particlar set of enttes represents. In
additonn they provide eetra inf ormaton aboct hotels (ncmber of rooms?.
Data inpct and cpdatnh are most tme-ionscminh.
Data manahement throchh DaMSn this is a set of iompcter prohrams f or orhanieinh
inf ormatonn at the iore of whiih will be a database.
It is the ability of GIS to transf orm spatal datan f rom one entty type to another – and to
perf orm spatal analysisn that distnhcishes GIS f rom other types of inf ormaton systems.
Chanhinh by addinh layers or speiif yinh layers and projeitnh these on a map.
Three types of ilassifiaton proiedcres:
- Those csed f or storahe and retrieval (presentaton iapabilites may allow the display
of a soil map of the area of interest?
- Constrained qceries that allow the cser to loos at paterns in their data. Usinh
qceries only iredible soils iocld be seleited f or viewinh or f crther analysis
- Modellinh proiedcres f or the prediiton of what data mihht be at a diferent tme
and plaie. Prediitons iocld be made aboct whiih soils are vclnerable.
A map ian only show so mcih layersn bct in GIS more ian be csed and speiifi seleitons ian
be made whiih will deirease the data whiih is viscalieed.
Form of data octpct csed will depend on iost ionstraintsn the acdienie to whom the resclts
are direited and the octpct f aiilites available.
,Chapter 2
Not all inf ormaton is needed if yoc want to fnd the shortest way to deliver a pieea. Yoc ian
leave oct and speiif y many elements = redcitonist natcre of GIS.
Data are observatons we mase f rom monitorinh the real world. Data are iolleited as f aits
or evidenie that may be proiessed to hive them meaninh and tcrn them into inf ormaton.
Data are basiially raw ncmbers whiih yoc ian mase csef cl by addinh ionteet.
Primary iolleited data: is whiih yoc have iolleited yocrself (iocntnh people?.
Seiondary iolleited data: iolleited by an orhanieaton (CaS?.
Data has three dimensions: temporaln themati and spatal.
Eeample with avalanihe
- Temporal: 10:30 14-02-2018
- Themati: wet slab avalanihe trihhered by two of-piste ssiers
- Spatal: three pines valleyn socth f aiinh slope
Maps and their infcenie on the iharaiter of spatal data.
Maps have shaped the way most of cs thins aboct spaie in two dimensions. Distniton
between themati and topohraphii maps. Themati shows data relatnh to a particlar
theme or topii (soil?. Topohraphii shows a diverse set of data on diferent themes.
Mappinh proiess:
- Establish the pcrpose of map
- Defne siale of map
- Seleit real world f eatcres whiih mcst be portrayed
- Choose method f or representaton of these f eatcres
- Generaliee f eatcres f or representaton in two dimensions
- Adopt a map projeiton f or plaiinh these f eatcres onto a fat pieie of paper
- Apply a spatal ref ereniinh system to loiate these f eatcres relatve to eaih other
- Annotate the map with seysn lehends and teet to f aiilitate cse of the map
Pcrpose of maps:
- To tcrn data into inf ormaton that will be iommcniiated to a third party
- To ionvinie the heneral pcblii that the war efort was hoinh well (WW2?
- To inf orm people aboct area if they are travellinhn these maps are more aiicrate
than propahanda maps.
Siale hives an indiiaton of how mcih smaller than reality a map isn rato of a distanie on the
map to the iorrespondinh distanie on the hrocnd. 3 ways to eepress siale: raton verbal or
hraphiial. Standard topohraphii maps iontain eeamples of all three. It shocld be
remembered that small-siale (1:1.000.000? maps are those that iover larhe areas.
Converselyn larhe siale (1:10.000? maps iover small areas and iontain larhe amocnt of detail
aasii symbols of maps: pointsn lines and areas.
Points: csed to represent f eatcres that are too small to be represented as area at siale.
Postboe or tree e.h. The data stored f or a postboe will inilcde heohraphii loiaton and
details of what the f eatcre is.
Lines: csed to represent f eatcres that are linear in natcre. Roads or rivers e.h. It is a strinh of
io-ordinates. Networss are an eetension of the line type.
Areas: represented by a ilosed set of lines and are csed to defne f eatcres scih as feldsn
bcildinhs or lases. Ref erred to as polyhonesn e.h. felds and lases. Some polyhons eeist on the
, hrocnd and whilst others are imahinary. Two types of polyhons: island polyhons and adjaient
polyhons. Island: oiicr in a variety of sitcatonsn not only islands bct also a spaie within a
feld. Speiial type of island polyhon: nested polyhonn is ireated by iontocr linesn set of
ionientrii rinhs. Adjaient polyhons are more iommon; feldsn postiode areas e.h.
Depends on the siale whiih fhcre yoc will cse.
Spatal data is heneralieaton of real-world f eatcres. Sometmes needed beiacse data are
reqcired at a particlar sialen or hive ilarity to an imahe or enhanie its major theme. River
smoothed oct in a map of the iocntry instead of river on loial siale. Relatonship between
detail and siale is ref erred to as siale-related heneralieaton.
Another problem is the siale of the width of the rivern if yoc cse real siale on bih mapn most
of the tmes the river will barely be visible.
Cartohraphii heneralieaton: iode of praitie.
1. Seleitonn seleitnh map f eatcre f or heneralieaton.
2. Simplifiatonn deiision how to simplif y the f eatcre.
3. Displaiementn displaie overlappinh or adjaient f eatcres so they are both visible in
the map.
4. Smoothinh and enhaniementn if data is f rom series of samplinh points smoothinh
teihniqce f or niie shape.
GIS mases the world fat so pctnh in and readinh data is easier. Diferent ways to mase the
earth fatn see pahe 44.
Rooms shaped lise:
- Ciriclarn there will be a iontncocs piitcre of the Earth. Eqcator is line of lattcde
nearest the wall and represents line of trce sialen alonh distanies are not distorted.
Top and botom of the wall the loiaton of iocntries is distorted. View of poles very
distortedn poles are inilcded on ocr projeit mapn the points representnh the north
and socth poles beiomes so distorted as to be projeited as a straihht-line eqcal in
lenhth to that of the eqcator.
Cylindrical projeitonsn where the scrf aie of the earth is projeited onto a iylinder
that eniompasses the hlobe. Scitable f or maps of an are that have only a small eetent
in lonhitcde.
- Sqcaren only a part of scrf aie Earth will be visible on the fat wall. Distorton will be
similar to that in the iiriclar room eeiept thatn sinie the sinhle wall is straihht and
not icrvedn the imahe of the world will be distorted al all f ocr edhes of the wall and
not only the top and botom.
Azimuthal
- Tepeen the line of trce siale is no lonher the eqcatorn bct some line of lattcde nearer
the north pole that lies at a tanhent to the slopinh walls of the tepee. The steeper the
wallsn the lower the lattcden the shallower the wallsn the hihher the lattcde.
Conic
See page 46 for visualizaton
Ref ereniinh system is csed to loiate f eatcre on the Earth’s scrf aie or a two-dimensional
representaton of this scrf aie scih as a map.
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