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Geographical Information System

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Geographical Information System

What is GIS?  A technology  ± hardwa hardware re & sof softwa tware re tool toolss

 An info inform rmat atio ion n hand handli ling ng stra strate tegy gy  The The obje objectiv ctive: e: to impro improve ve over overall all decisi decision on making 2

GIS: a formal definition ³A system for capturing, storing, checking, integrating, manipulating, analysing and  displaying data which are spatially referenced to the Earth. This is normally considered to involve a spatially referenced  computer database and appropriate applications software´ 3

GIS definition ³« a special case of information system where the database consists of observation son spatially distributed features, activities or events, which are definable in space as points, lines or area. A geographic information systems manipulates data about these points, lines and areas to retrieve data for ad hoc queries and analyses´

Why is GIS unique?  GIS GIS han handl dles es SPA SPATI TIAL AL info inform rmat atio ion n  ± Informat Information ion referen referenced ced by by its location location in in space

 GIS makes makes connec connection tionss betwee between n activ activitie itiess  based on spatial proximity


GIS concepts are not new!  Lond London on chol choler eraa epi epide dem mic 18 1854


+ Cholera death Water pump


GIS: historical background This technology has developed from:  ± Digita Digitall cartogr cartograph aphy y and and CAD  ± Data Data Base Manage Manageme ment nt Syste Systems ms ID 1 2










CAD System

Data Base Management System 7

Digital Digital Mapping Mapping Computer   Aided  Aided Design esign




Surveying urveying Remote Sensing

Cross-di Cross-disc sciiplin plinary ary nature of GIS GIS

GIS components Spati patial data

GI Computer  Comput Computer er hardw hardware are / software tools



Speci pecif ic appli applicati cations / deci decision making making objecti objectives 9

What makes data spatial? Gr id coco-ordin -ord ordin inate ate

Place lacen name

Lat atiitude / Longi ngitude tude Postcode Descr ipt ptiion

Dista Di stan nce & bear ing ing


Characteristics of spatial data  Location 


Kingsto ingston n Univers Universiity,P ty,Pe enrhynR rhynRo oad

Post Code:


 Grid 



518106.72 168530.37

.38´W , 49° 49° 36¶ 17.6 17.62´ 2´N N Latitude/Longitude: 0° 21¶ 55.38´W


Characteristics of spatial data Geometry

 The shape of a  building or county  The course of a ri river, the route of a road  The shape of th the landscape, landscape, relief 


Characteristics of spatial data 

Topology y

Connected to




Adjacent to


 North of . . .


W ithin ithin

the Royal Borough of Kingston-upon-Thames King ston-upon-Thames


Opposite the Surrey County Council building 


 North of Surbiton station


 Adjacent to Penrhyn Road 


Spatial Data: examples  Socio ocio-e -eccono onomic data ata  ± Region Regional al health health data data  ± Consume Consumerr / lifest lifestyle yle profiles profiles  ± Geode Geodemo mogr grap aphic hicss

 Env Environ ironm mental ntal data data  ± Topog Topogra raph phic ic dat dataa  ± Themati Thematicc data, data, soils, soils, geolog geology y 14

Data Modelling Modelling - step 1  Features

 ± Building ldings s  ± Road cen centrelin trelines es  ± Lamp column columns ± Gas p ipes  ± CTV A TV Access ccess covers  ± Road surfaces


Data Data Mode Modell llin ing g - step step 2 Poin intt Line Lin e Poly olyg gon


Data ata Mod Model elli ling ng - step step 3


Object: Enttity: En

Build lding ing Poly olyg gon Tour ist Informat In formatiion Bureau 17


Name :  Address:  A ddress: Tow own n: Owner: Tel el.. No: Floor space

Next 5 Market Place King ingsto ston n Ms J Shore 0181 547 1245 1300 sq m


Spatial data storage 7,10 5,9



 Vector model


polygon 8,6

1,6 6,6



line point





 Raster model

as geometric objects:  points, lines, polygons


as image files composed of grid-cells (pixels)


Spatial data storage model  import important ant in in determ determini ining ng the the poten potential tial applica applicatio tions ns of of the sys system tem  model model may also also affec affectt the type type of analys analysis is work work that can be achieved  hybri hybrid d approach approach to stor storing ing grap graphic hical al and and attrib attribute ute inform informatio ation n  Attrib Attribute ute inform informatio ation n often often stor stored ed with within in stand standard ard relat relation ional al database  Graphi Graphical cal inform informatio ation n is stored stored in a propri proprietar etary y file file sys system tem  ± optim optimis ised ed tool toolss for for data data handl handling ing  ± although although non-st non-standar andard d proprieta proprietary ry system system will will be difficul difficultt to integrate with other systems, it will tend to be very efficient at handling large graphics files.

Vector data model 

advantag advantagee of of the vector vector data data format: format: allows allows precise precise represent representati ation on of   points, boundaries, and linear features.  ± useful useful for for analys analysis is tasks tasks that require require accur accurate ate positio positioning ning,,  ± for defining defining spatial relationship relationship (ie the the connectivi connectivity ty and and adjacency adjacency))  between coverage features (topology), important for such purposes as network analysis (for example to find an optimal op timal path between two nodes in a complex transport network)

main main disad disadvant vantage age of vector vector data is that that the boundaries boundaries of the the result resulting ing map polygons are discrete (enclosed by well-defined boundary lines), whereas in reality the map polygons may represent continuous gradation or gradual change, as in soil maps.

Raster data model 

good good for for rep repre rese sent ntin ing g indi indist stin inct ct bou bounda ndari ries es  ± thematic thematic informa information tion on soil types, types, soil moisture, moisture, vegeta vegetation, tion, ground ground temperatures

as reconnais reconnaissanc sancee satell satellite itess and and aerial aerial surveys surveys use rasterraster-base based d scanners, the information (ie scanned images) can be directly incorporated into GIS

the the highe higherr the the grid grid resolu resoluti tion, on, the the large largerr the data data file file is goin going g to be

Modelling the real world y

1 1 20 50 1 2 24 45 1 3 52 55 2 1 0 45 46 40 x


000000020 000001000 020010000 000020000 2 2 2 0 1 ...


Vector data

Land use parcels


Raster data


Manipulation and analysis  What hat wou would happ happen en if . . .  A chemical leaked into a river?  Where does . . . The Green Belt exist in relation to the City?  Has . . .  Population changed over the last ten years?  Is the there re a spa spati tial al patt patter ern n rel relat ated ed to . . . Car ownership in our area? 26

Databases & GIS Spatial data

 At a simple le level a GIS may just form the graphical interface to a database  The The majority of GI GIS applications follow this example

MapIn Map Info fo

Linked database table

SQL Query Manager 

Geo-relational Data Models  Linked Linked tables tables bas based ed on on the the relati relationa onall mode model, l,  but storing geographical information such as:  ± Geom eometry etry  ± Topol opolo ogy  ± Attr Attrib ibut utes es

GIS & Analysis In the context of GIS, analysis is... ³ Deriving new information from existing data´  It is also the manipulation of data to solve a problem within n 500m of a lake e.g. identify all areas withi Increasing use is made of the analytical capabilities of GIS, BUT many GIS projects only use the software to store and manage geographical data Yet analysis often relies on many simple basic GIS techniques

Simple Query  The identi identific ficatio ation n of objects objects and their their attrib attribute utess either by location or attribute query.

MapIn Map Info fo

Buffering  Crea Creati tion on of an are areaa of inte intere rest st arou around nd an an objec objectt  ± proximi proximity ty analys analysis is and environm environmenta entall impact impact assess assessmen ment. t.

MapIn Map Info fo

Cookie Cutting  Overla Overlay y of datase datasets ts usin using g one one datase datasett as a siev sievee or  cookie cutter to select a subset of the other dataset.

MapIn Map Info fo

Overlays  Layer: ayer: A them themati aticc plan planee of GIS GIS feat featur ures es cont contain ainin ing g geographically and logically related data 

Overlay Overlaying ing involve involvess superim superimposin posing g two two or or more map layers layers to produce produce a new map layer.

Examp Example: le: a new gene genetic ticall ally y enginee engineered red vari variety ety of of wheat wheat grow growss well well in dry dry environments, with long growing seasons and alkaline soils. Given the availability of data on the length len gth of the growing season, moisture regime and soil alkalinity, where is the best place to plant the wheat?  ± overlay overlaying ing (superimpo (superimposing) sing) several several maps maps showing showing (separa (separately tely)) water-budge water-budget, t, growing season length, soil pH, sodium content, and so on. The GIS analysis can establish the locations where all the favorable soil conditions coincide, as the places where the wheat will grow best.

its The benef its

of GIS include:

 Bette Betterr inf infor orm matio ation n man manag agem emen entt  High Higher er qual qualit ity y anal analys ysis is  Abili Ability ty to to carr carry y out out ³wha ³whatt if?´ if?´ scen scenar ario ioss  Impr Improv ovee proj projec ectt effi effici cien ency cy 36

GIS Applications  Faci Facili liti ties es manag anagem emen entt  Marke arketi ting ng and and reta retail ilin ing g  Environmental  Tran Transp spor ort/ t/ve vehi hicl clee rout routin ing g  Health  Insurance and many more . . . 37

Function of GIS Point-in-polygon Queries

Proximity Queries Questions involves proximity: ³what objects are within a certain distance of this tower?´ These questions can be answered by the means of  µBuffer¶ A region surrounding the area of interest for a given distance.

 Network Queries Defining Network: A set of linear features that are all interconnected, whose primary purpose is to direct the movement movement of some commodity from one point to another. Example: Highways, Streets, Railways, etc.

Route Optimization Defines the what is is the best way to get from A to B with the conditions of shortest time to travel and distance. Such queries could be commonly used by emergency service like fire, police or delivery vehicles, salesperson, etc.  Network load Queries Involve predictions of the response of a network n etwork to an event. Example: How a sewer network will respond to a heavy rainfall. Effect of construction on a given stretch of road on traffic flow

Thematic Mapping Allow the user to present the data in a way that allows for quick and easy recognition of pattern that could not be seen by just looking at a table of  numbers. Superimposing Superimposing two two different thematic maps allows the viewer to visually find any relationship  between two variables

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