2-200305220204.pdf

GEOGRAPHIC INFORMATION SYSTEM (GIS)
MASHHOOD ARIF

Contents
What is GIS?
Components of GIS
GIS Process
Functions of GIS
Applications of GIS
Data Structure
Data File Formats
Map & Map Elements
 Data Modelling
 GIS Data Sources
 Geospatial Analysis
 Conclusion

What is GIS?
“A system for capturing, storing, checking, integrating, manipulating, analyzing
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”
A set of tools for
 Collecting
 Storing
 Manipulating
 Retrieving
 Transforming and Display of Spatial Data from the Real World

GEOGRAPHIC implies that locations of the data items are
known, or can be calculated, in terms of Geographic
coordinates (Latitude, Longitude)
INFORMATION implies that the data in a GIS are organized to
yield useful knowledge, often as colored maps and images, but
also as statistical graphics, tables, and various on-screen
responses to interactive queries
SYSTEM implies that a GIS is made up from several inter-
related and linked components with different functions. Thus,
GIS have functional capabilities for data capture, input,
manipulation, transformation, visualization, combinations,
query, analysis, modelling and output

Components of GIS
GIS links locational (spatial) and database (tabular) information and enables a
person to visualize patterns, relationships and trends. The five components of GIS
are as under:
1. Hardware
2. Software
3. Data
4. People
5. Methods

 Hardware
Systems to support rapid graphic analysis and processing
(CPU, processor, keyboard etc.)
 Software
A technology for storing and analyzing location and
attribute data (ArcGIS, Map Info, AutoDesk Map etc.)
 Data
Geographical data in form of hardcopy map, digital map,
aerial photos, satellite images, other documents for GIS
operations
 Methods
Various procedures including analysis, manipulation, presentation,
visualization, modelling
 People
Different user and GIS application experts

GIS Process
Links databases and maps
Manages information about places
Helps answer questions such as:
 Where is it?
 What else is nearby?
 Where is the highest concentration
of ‘X’?
 Where can I find things with
characteristic ‘Y’?
 Where is the closest ‘Z’ to my
location?

Functions of GIS
 Data Capture
 Data Storage & Management
 Data Display
 Data Editing, Manipulation and Analysis
 Presentations & Visualization

Applications of GIS
 Agriculture Archaeology
 Architecture/Landscape Arch.
 Business Computer Science
 Environmental Science
 Engineering
 Journalism
 Military Science
 Natural Resource Management
 Geography
 Geology
 Meteorology
 Oceanography
 Law Enforcement
 Public Health
 History
 Sociology
 Urban/Regional Planning

GIS Data Formats (file formats)
Shapefiles
Coverages
TIN (e.g. elevation can be stored as TIN)
◦ Triangulated Irregular Network
Grid (e.g. elevation can be stored as Grid)
Image (e.g. elevation can be stored as image, all remote
sensing images)
Vector data
Raster data

Shape Files
 Nontopological
 Advantages no overhead to process topology
 Disadvantages polygons are double digitized, no topologic data
checking
 At least 3 files .shp .shx .dbf

Coverages
Original ArcInfo Format
Directory With Several Files
Database Files are stored in the Info Directory
Uses Arc Node Topology
Containment (coincident)
Connectivity
Adjacency

TIN
A triangulated irregular network (TIN) is a data model
that is used to represent three dimensional objects.
In this case, x,y, and z values represent points.
Using methods of computational geometry, the points
are connected into what is called a triangulation, forming
a network of triangles. The lines of the triangles are called
edges, and the interior area is called a face, or facet.
The illustration shows how we can create a TIN of the terrain
 First, a series of elevation points are created
 Second, a TIN face is created with the elevation data
 Third, the faces are shaded in to give the impression of a 3D surface

Map & Map Elements
 Maps provide two types of information: Locational Information and Spatial
Relationships
 Maps contain POINT features, LINE features and AREA features
Point Features Line Features Area Features
Spatially distributed entities,
activities or events
Points have a single geographic
coordinate such as: Tree, traffic
accident, lamp post
activities or events
Lines (Arcs) are a series of
geographic coordinates joined to
form a line such as: Road, stream,
railway
activities or o events
Areas (Polygons) are a series of
geographic coordinates joined
together to form a boundary such
as: Lake, soil types

Data Modelling
Step 1
Step 2
Step 3

GIS Data Sources
Existing data
Digital
Map and Plan
Paper Files
Low Cost
Acquisition
Remote Sensing
Photogrammetry
Field Survey
High Cost

Geospatial Analysis
 Geography + GIS = Geospatial
 An approach to applying statistical methods and other
informational techniques to data which has a geographical or
geospatial aspect
 Such analysis would typically employ software capable of geospatial
representation and processing, and apply analytical methods to
terrestrial or geographic datasets, including the use of GIS

Operations
Surface analysis
In particular analyzing the properties of physical surfaces, such as gradient,
aspect and visibility, and analyzing surface-like data “fields”
Network analysis
Examining the properties of natural and man-made networks in order to
understand the behavior of flows within and around such networks; and
locational analysis
Geovisualization
The creation and manipulation of images, maps, diagrams, charts, 3D views and
their associated tabular datasets

Conclusion
GIS is a broad term that can refer to a number of different
technologies, processes, and methods
It is attached to many operations and has many applications related
to engineering, planning, management, transport/logistics,
insurance, telecommunications, and business
Modern GIS technologies use digital information, for which various
digitized data creation methods are used
Many disciplines benefit from GIS

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