GIS

Contents

1. Definition 2. Uniqueness 3. Background 4. GIS components 5. Characteristics of spatial data 6. Spatial Data Modelling 7. Spatial data storage and Comperison 8. Modelling in real world 9. Database and GIS10. Benefits and Applications of GIS

GIS: a formal definition

“A system for capturing, storing, capturing, storing, checking, integrating, manipulating, checking, integrating, manipulating, analysinganalysing and displayingdisplaying data which are spatially referenced to the Earth.”

This is normally considered to involve a spatially referenced computer database and appropriate applications software.

Why is GIS unique?

➲ GIS handles SPATIAL information Information referenced by its location in space

➲ GIS makes connections between activities based on spatial proximity

GIS concepts are not new!➲ London cholera epidemic 1854

Cholera deathCholera death

Water pumpWater pump

GIS: background

This technology has developed from: Digital cartography and CAD Data Base Management Systems

1

2

3

ATTRIBID X,Y123

ID123

CAD SystemCAD System Data Base Management SystemData Base Management System

DigitalDigitalMappingMapping

Photo-Photo-grammetrygrammetry

ComputerComputerAidedAided

DesignDesign

SurveyingSurveying

RemoteRemoteSensingSensing

DatabasesDatabases

GISGIS

Cross-disciplinary nature of GIS

GIS components

Relation between GIS components

Specific applications / decision making objectives

G I SG I S

Spatial data

Computer Computer hardware / / software toolssoftware tools

What makes data spatial?

PlacenamePlacenameAddressAddress

PostalCodePostalCode

DistanceDistanceDescriptionDescription

Latitude/Longitude Latitude/Longitude

Characteristics of spatial data

Geometry➲ The shape of a

building or county➲ The course of a river➲ The route of a road➲ The shape of the

landscape


➲ Topology• Connected to . . .

• Within . . .

• Adjacent to . . .

• Opposite of . . .

• North of . . .

• Opposite of the Main Hostel building

• Adjacent to M.G. Road

• North of HOWRAH station


➲ Location with Attributes

Name : Samhati Soor Address: 5 Market Place Town: Contai Tel. No: 03220-287871 Floor space: 1300 sq ft Postal Code: 721401 Latitude: 21.78° N Longitude: 87.75° E

• Features

– Buildings– Road centrelines

– Lamp columns

– Gas pipes– CTV Access covers– Road surfaces

Spatial Data Modelling - step 1


Point

Line

Polygon


Feature : BuildingObject: PolygonEntity: Tourist

Information Bureau

Spatial data storage

➲ Vector model

➲ Raster model

point

1,6

2,5

5,4

4,1

7,105,9

4,7

6,68,6

9,8

line

polygon

2,2

5 10

5

10

as geometric objects: points, lines, polygons

as image files composed of grid-cells (pixels)

Comparison between vector model and raster model

VECTOR

Advantages:1.Good representation of reality2.Compact data structure3.Topology can be described in

a network4.Accurate graphics

RASTER

Advantages:1.Simple data structure2.Easy overlay3.Various kinds of spatial

analysis4.Uniform size and shape5.Cheaper technology

Disadvantages:1.Large amount of data2.Less “pretty”3.Projection transformation is difficult4.Different scales between layers can be a nightmare5.May lose information due to generalization

Disadvantages:1.Complex data structures2.Simulation may be difficult3.Some spatial analysis is difficult or impossible to perform

Modelling in real world

1 1 20 50

1 2 24 45

1 3 52 55

2 1 0 45 46 40

...

0 0 0 0 0 0 0 2 0 0 0 0 0 0 1 0 0 0 0 2 0 0 1 0 0 0 0 0 0 0 0 2 0 0 0 0 2 2 2 0 1 ...

x

y

Databases & GIS

• At a simple level a GIS may just form the graphical interface to a database

• The majority of GIS applications follow this example Linked database tableLinked database table

Spatial datSpatial dataa

SQL Query ManagerSQL Query Manager

MapInfoMapInfo

Databases & GIS

The benefits of GIS include:

➲ Better information management

➲ Higher quality analysis

➲ Ability to carry out “what if?” scenarios

➲ Improve project efficiency

GIS Applications

➲ Facilities management➲ Marketing and retailing➲ Environmental➲ Transport/vehicle routing➲ Health➲ Insurance

and many more . . .

References

1.https://www.llnl.gov/str/September02/pdfs/09_02.2.pdf 2.Geographic information system - Wikipedia, the free

encyclopedia 3.http://www.gim-

international.com/download/whitepaper_uploadfile_3.pdf 4.GIS (geographic information system) - National Geographic

Education 5.OECD Glossary of Statistical Terms - Geographic

information Definition 6.What is GIS (Geographic Information Systems)? A Word

Definition From Webopedia 7.http://www.nwgis.com/gisdefn.htm 8.GIS OUTLINE www.grossmont.edu 9.What Is GIS? | Geographic Information Systems www.esri.com10.http://unstats.un.org/unsd/publication/SeriesF/SeriesF_79

E.pdf

Technology

GIS