GIS

2. 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 GIS
10. Benefits and Applications of GIS

3. 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.

4. Why is GIS unique?
➲ GIS handles SPATIAL information
Information referenced by its location in space
➲ GIS makes connections between activities
based on spatial proximity

5. GIS concepts are not new!
➲ London cholera epidemic 1854
Cholera deathCholera death
Water pumpWater pump

6. GIS: background
This technology has developed from:
 Digital cartography and CAD
 Data Base Management Systems
1
2
3
ATTRIBID X,Y
1
2
3
ID
1
2
3
CAD SystemCAD System Data Base Management SystemData Base Management System

7. DigitalDigital
MappingMapping
Photo-Photo-
grammetrygrammetry
ComputerComputer
AidedAided
DesignDesign
SurveyingSurveying
RemoteRemote
SensingSensing
DatabasesDatabases
GISGIS
Cross-disciplinary nature of GIS

8. GIS components

9. Relation between GIS components
Specific applications /
decision making objective
G I SG I S
Spatial data
ComputerComputer hardware //
software toolssoftware tools

10. What makes data spatial?
PlacenamePlacenameAddressAddress
PostalCodePostalCode
DistanceDistance
DescriptionDescription
Latitude/LongitudeLatitude/Longitude

11. 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

12. Characteristics of spatial data
➲ 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

13. Characteristics of spatial data
➲ 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

14. • Features
– Buildings
– Road centrelines
– Lamp columns
– Gas pipes
– CTV Access covers
– Road surfaces
Spatial Data Modelling - step 1

15. Spatial Data Modelling - step 2
Point
Line
Polygon

16. Spatial Data Modelling - step 3
Feature : Building
Object: Polygon
Entity: Tourist
Information
Bureau

17. Spatial data storage
➲ Vector model
➲ Raster model
point
1,6
2,5
5,4
4,1
7,10
5,9
4,7
6,6
8,6
9,8
line
polygon
2,2
5 10
5
10
as geometric objects:
points, lines, polygons
as image files
composed of grid-cells
(pixels)

18. Comparison between vector model and
raster model
VECTOR
Advantages:
1.Good representation of reality
2.Compact data structure
3.Topology can be described in
a network
4.Accurate graphics
RASTER
Advantages:
1.Simple data structure
2.Easy overlay
3.Various kinds of spatial
analysis
4.Uniform size and shape
5.Cheaper technology
Disadvantages:
1.Large amount of data
2.Less “pretty”
3.Projection transformation is
difficult
4.Different scales between
layers can be a nightmare
5.May lose information due to
generalization
Disadvantages:
1.Complex data structures
2.Simulation may be difficult
3.Some spatial analysis is
difficult or impossible to perform

19. 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

20. 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

21. Databases & GIS

22. The benefits of GIS include:
➲ Better information management
➲ Higher quality analysis
➲ Ability to carry out “what if?” scenarios
➲ Improve project efficiency

23. GIS Applications
➲ Facilities management
➲ Marketing and retailing
➲ Environmental
➲ Transport/vehicle routing
➲ Health
➲ Insurance
and many more . . .

24. 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.com
10.http://unstats.un.org/unsd/publication/SeriesF/SeriesF_79
E.pdf