INTRODUCTION TO GIS PART II

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INTRODUCTION TO GIS PART II

• By
• Dr. Baqer Al-Ramadan,
• City and Regional Department
• College of Environmental Design
• King Fahd University of Petroleum and Minerals

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Presentation Outline

• Features Representation in Maps and GIS
• The Layers Concept in GIS
• Typical Layers in a GIS Database
• Descriptive Attributes in GIS
• GIS Components and Functional Elements
• GIS Functions
• Data Input Systems
• Data Output Peripherals
• Sources of Geographic Information

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Features Representation in Maps

• Features are represented as set of points, lines,
  and areas (polygons)
  
• Points represent geographic phenomena too small
  to be depicted as lines or areas
  
• water wells,
• telephone poles
• Lines represent geographic objects too narrow to
  depict as areas
  
• streets ,
• rivers

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• Areas represent the shape of homogenous features
  
  
• Country, island, or lake boundary,
• Parcels,
• Land use zones

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FeaturesRepresentation in GIS

• Features are represented as points, lines, and
  areas
  
• Points as single x,y locations
• Lines as a series of ordered x,y coordinates
• Areas (polygons) as a series of x,y coordinates
  defining line segments that enclose an area

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Real-world entities are abstracted into three
basic shapes
Representation of features in GIS
Points, Lines, and Polygons
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The Layers Concept in GIS

• In a GIS, map features are organized into a set
  of layers or themes of information
  

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Typical Layers in a GIS Database

• Basemap layer
• Geodetic control points
• Contour lines
• Permanent geographic features such as coastlines
  and rivers
  
• Land parcels layer
• Roads network layer

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• Utilities network layers
• Electric,
• Phone,
• Water, and
• Sewer networks

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Descriptive Attributes in GIS

• Descriptive attributes stored in a predefined
  format files as
  
• sets of characters
• string of values
• These files referred to as Feature Attribute
  Tables (FAT)
  
• Each row is a record for a single feature
• Each column is a field for all features

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• One-to-one correspondence between each feature
  and its descriptive attributes

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GIS Components

• Software
• Hardware
• Database
• Users

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GIS Functional Elements

• Data Input
• Data Output
• Data Manipulation and Analysis

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Data Input

• Is the first step in developing the database for
  GIS
  
• One of the greatest operational problems and
  costs in the development of any GIS
  
• The cost of building the data base is commonly 5
  to 10 times the cost of GIS hardware and software
  together
  
• Hence, data input is usually the major bottleneck
  in implementing GIS

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Data Output

• GIS provides means to document and present
  findings as
  
• Maps
• Reports of findings that include
• Attribute tables
• graphic products Bar and Pie Charts

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Data Manipulation and Analysis

• At the core of GIS and this is where the
  justification to acquire GIS is usually made
  
• It is what differentiates it from other
  traditional types of information systems

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GIS functions
Customers
Buildings
Streets
Reality
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Capturing data
Digital data
Hardcopy maps
Coordinates
480585.5, 3769234.6 483194.1, 3768432.3 485285.8
, 3768391.2 484327.4, 3768565.9 483874.7, 376982
3.0
GPS
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Storing data

• Vector formats
• Discrete representations of reality
• Raster formats
• Use square cells to model reality

Reality(A highway)
Rows
X,Y
Columns
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Query

• Identify specific features
• Identify features based on conditions

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Analysis
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Display
Graphs
Maps
Reports
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Output
Internet
Paper map
Document
Image
Florida.mxd
Florida.jpg
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Data Input Systems

• There are two common systems of data input in
  GIS
  
• Manual Digitizing
• Automated Scanning

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Manual Digitizing

• Done through a digitizer
• Contains a magnetic surface on which the map to
  be digitized is placed on
  
• Coordinates are entered through a cursor
• Slow and costly
• Accurate results

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Automated Scanning

• Maps are scanned through a scanner
• Faster and lower cost
• Typically requires a substantial amount of
  editing
  
• Lower accuracy

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Data Output Peripherals

• Plotters
• Printers

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Sources of Geographic Information

• Hard copy and digital Maps
• Aerial photographs
• Satellite images

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• Commercial satellites providing Images
• EOSAT Earth Observation Satellite Company at
  USA
  
• SPOT Image Corp A French Satellite
• IKONOS
• Still not very useful for applications that
  require high accuracy and resolution