Geographical Information

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Geographical Information System
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CONTENTS

• GEOGRAPIC INFORMATION
• GIS FUNDAMENTALS
• SPATIAL INFORMATION
• CHARACTERISTICS OF MAPS
• DIGITISATION
• LAYERING
• GIS BENEFITS
• GIS APPLICATIONS
• CUSTOMISED GIS PACKAGE OF OFC NETWORK FOR
  GAIL

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GEOGRAPHY MATTERS
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GEOGRAPHIC INFORMATION

• Information about places on Earths Surface
• Knowledge about where something is...
• Knowledge about what is at a given location...

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GIS Overview

• Every object present on the Earth can be
  geo-referenced - The fundamental key of
  associating any database to GIS.
• The term 'database' refers to collection of
  information about things their relationship to
  each other.
• Geo-referencing' refers to the location of a
  layer or coverage in space defined by the
  co-ordinate referencing system.

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GIS - Geographic Information System
GIS is a System of software, hardware, data
and personnel to help manipulate, analyze
and present information that is tied to a
spatial location
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Spatial Data

• Data which has locational characteristics and
  which can be represented on a map is called
  spatial data.
• Spatial Data tells us where the objects of
  interest are located, their distributions and
  extent.Examples are street atlas, tourist guide
  map etc.

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Data Representation
RASTER VECTOR REAL WORLD
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Raster Data Model

• Characteristics
• Simple 'grid' structure of rows and columns.
• Based on cells or picture elements (pixels).
• Linear feature (e.g. a road) is a contiguous set
  of cells.
• Resolution based on size of grid (cell) -gt the
  smaller the cell, the higher the resolution.
• Features are considered homogenous within a
  pixel.
• Storage increases with the square of the
  resolution.

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Vector Data Model

• Characteristics
• Based on objects (points, lines, areas).
• Constructed using arcs, nodes and
  vertices.
• Resolution can be independent of detail.
• Every point has a unique location.

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DATA FOR GIS APPLICATION
Digitized and Scanned Maps Databases GPS
(Global Positioning system) Satellite Image
Aerial Photography
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GPSGLOBAL POSITIONING SYSTEM

• First available for Govt. use in late 70s.
• Now available for Business use in form of
  Handled receivers.
• Used as an Input for GIS for precise
  positioning of Geo-Spatial data and its
  collection.

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GPS Technology

• In GPS Technology 24 Satellites are orbiting
  the earth. Each equipped with atomic clocks
  and can send radio signals to exact time and
  locations. These radio signals are picked by
  GPS receivers handled by the users.
• Once the GPS Receiver locks on to four or
  more of these satellites it can triangulate
  its location .

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MAP

• A map is a graphic representation of some part
  of the earths surface.
• It contains a series of themes or coverage that
  are often combined to form the final product.
• Map also contains descriptive information
  which helps the reader interpret the
  information on the map.

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Need for a map to be used

• Some of these decisions taken without a map
  may turn out to be uneconomical.
• The mere tabular analysis does not reveal
  correlation between two entities due to their
  spatial proximity.
• Spatial proximity and their influence is an
  important characteristic in deciding the location
  of service points, in distribution and in
  revealing spatial patterns.
• Conventionally business decisions were taken by
  analyzing attribute data stored in tables..

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Map Scale
Scale describes the relation between a single map
unit to the number of same units in the real
world. Example - 1 1000 (1 inch 1000
inches) Scale Bar compares the map units to an
established real-world unit of measure. Example
- 1 inch 2.5 miles
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Resolution

• The accuracy with which a given map scale can
  depict the location and shape of map features.
• The larger the map scale , the higher the
  possible resolution.
• As map scale decreases, resolution diminishes
  and feature boundaries must be smoothed,
  simplified or not shown at all.
• Resolution plays a large role in GIS, especially
  in Raster -based modeling.

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Projection System

• Maps are flat, but the surfaces they represent
  are curved. Transforming, three-dimensional space
  onto a two dimensional map is called
  "projection". This process inevitably distorts at
  least one of the following properties
• Shape,
• Area,
• Distance,
• Direction, and often more.
• It is known that a globe is a true representation
  of the earth, which is divided into various
  sectors by the lines of latitudes and longitudes.
  This network is called 'graticule'. A map
  projection denotes the preparation of the
  graticule on a flat surface.

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DIGITIZATION
Spatial data is available mostly in analog form
i.e. in form of maps and Arial photographs.The
process of converting an analog data into digital
form is digitization. It is the most important
technique of data input and storage in
GIS. Expensive Time Consuming Technique.
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TYPES OF DIGITAZATION TECHNIQUES

• MANUAL DIGITIZATION
• HEADS UP OR ONSCREEN DIGITIZATION

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MANUAL DIGITIZATION
Carried out on a Digitization table containing a
mouse like device called PUCK. Digitization
table is embedded with fine wires forming grid
like structure on which maps are mounted. Puck is
used to convert each and every point on the map
to digital form.
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Heads Up / On Screen Digitization
Maps to be digitized are already in Raster
Form Converts digital image in a form usable in
GIS Environment i.e. Each feature on the map has
a geographic coordinate associated with it.
Control Points with known geographic locations
are identified. Based on which geographic
coordinates of all the features in map are known.
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Heads Up / On Screen Digitization (Contd)
PAPER MAP
Scanner
Heads Up digitization
RASTER MAP
DIGITIZED GIS USABLE MAPS
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Features of a Digitized Map

• Line -coordinate positions of start and end
  points are recorded .Curved lines are broken
  into series of straight lines.
• Point - individual locations are recorded
  generating a coordinate pair.
• Polygon - Series of closed and interconnected
  lines .

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Map in the form of digital data Objects
(Feature) Polygons (Lakes, Forests) Lines (Roads,
Power lines) Points (Telephone Mast, Wells)
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ACCURACY IN DIGITIZATION
Spatial Accuracy of features depicted in
digitized maps is very important for a good
database. Types of Errors Geodetic Improper
Choice of Projection System. Machine Errors
inherent error, cant be removed, can only be
minimized . Manuscript Errors due to bad
quality of source maps.
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TYPES OF INFORMATION IN DIGITAL MAPS

• Geographic Information provides position of
  each map feature.
• Attribute Information describes specific map
  features but not graphics.
• Eg Attribute associated with a road might be
  its Name or Width .
• Display Information How a map is to be
  displayed. It features colours, line width ,
  polygon types.

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LAYERING
GIS software has a system of layers which can be
used to divide large maps into manageable
pieces. Example - Roads on one layer,
Hydrographic features on other layer.
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DIFFERENT DATA LAYERS
RIVER
CAPITALS
ROADS
STATES
LAKES
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GIS BENEFITS

• Fast Decision Making
• Efficient Management Information Base
• User Friendly
• Changes can be incorporated easily
• Explore large study areas
• Can cope up with loads of data.
• Data Integration
• Generates New Understanding

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GIS APPLICATION AREAS

• Public Information Service
• Land use and Growth planning
• Infrastructure management and planning
• Crime Tracking and Law Enforcement Planning
• Vehicle Routing and Traffic Management
• Business Development
• Community Development Planning
• Public Health and Risk Analysis
• Emergency Management
• Geo Positioning System
• Remote Sensing

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CUSTOMIZED GIS PACKAGE FOR OFC NETWORK FOR GAIL
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Introduction
GAIL wishes to implement a GIS based ASSET
MANAGEMENT SYSTEM which would help them to
monitor ,manage and record activities related to
OFC network . Objective is to have a single point
management information system for maintenance of
OFC.
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Scope
Creation of land base maps Integration of OFC
network on to them with reference to AS BUILT OFC
cable network diagram. Customized software
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PROTOTYPE