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GIS - An Introduction

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					Geographic Information System
       An Introduction
     Geographic information
• Information about places on the earth’s
  surface
• Knowledge about where something is
• Knowledge about what is at a given location
• Can be very detailed or very coarse
• Often relatively static
• Can be very voluminous
    Geographic information
        technologies
• Technologies for collecting and dealing
  with geographic information
• Three main types:
  – Global Positioning System (GPS)
  – Remote sensing
  – Geographic Information System (GIS)
                     GPS
• System of earth-orbiting satellites transmitting
  precisely timed signals (a similar system of
  Russian Federation: GLONASS - global
  navigation satellite system)
• Signals are received by a special electronic
  device
• Provides direct measurement of position on
  the Earth's surface
• Location is expressed in latitude/longitude or
  other standard system
           Remote sensing
• Use of Earth orbiting satellites to capture
  information about the surface and
  atmosphere below
• Satellites vary depending on how much detail
  can be seen, what parts of the
  electromagnetic spectrum are sensed
• Signals transmitted to Earth receiving stations
  where they are transformed for dissemination
  as digital images
                     GIS
• A system for input, storage, manipulation, and
  output of geographic information
• A class of software
• A practical instance of a GIS combines
  software with hardware, data, a user, etc., to
  solve a problem, support a decision, help to
  plan
• The next section is a basic introduction to GIS
              What is GIS?
• Stands for "geographic information
  system"
  – Is a special kind of "information system”
     • information systems are used to work
       (manipulate, summarize, query, edit, visualize)
       with information stored in computer databases
  – Uses special information about what is
    where on the Earth's surface
  What does a GIS look like?
• Two distinct meanings of the question
  "is this a GIS?”
  – 1. GIS is a real application, including the
    hardware, data, software and people
    needed to solve a problem (a GIS
    application)
  – 2. GIS is a type of software
• (focus on #1 first)
                  GIS hardware
• Like any other computer
   – Keyboard, display monitor, cables, Internet connection
• With some extra components perhaps
   – Maps come on big paper
       • Need big printers and plotters to make map output from GIS
       • Need big devices to scan and input data from maps to GIS
           – Digitizers, scanners

   – But not all GISs will need these
 What is important is the kind
 of information that's stored
• Information about what is where
  – The contents of maps and images
• Computer is used for GIS because the
  data stored in it would include maps and
  images
    Tools to do things with this information
•   Special functions that work on geographic information
     – Display on the screen
     – Edit, change, transform
     – Measure distances, areas
     – Combine maps of the same area together
•   Those were simple, but functions can be much more sophisticated
     – Keep inventories of what is where
     – Manage properties, facilities
     – Judge the suitability of areas for different purposes
     – Help users make decisions about places, to plan
     – Make predictions about the future

•   These sophisticated functions require human expertise as well
The functions that a GIS can perform
       are part of its software
• The second meaning above - a GIS is a type of
  software
• The user combines the software with his or her data
  and performs various functions
• This software will probably have been supplied by a
  company that specializes in GIS
• The price of the software may be anywhere from $50
  to $50,000
• There are many different GIS software vendors
   – Some specialize in GIS

   – For others, GIS is one of many markets for their products
What does I means “doing GIS”?
• Using the tools of GIS to solve a problem
• Helping to build the tools
   – Adding to existing geographic information technologies
   – Helping to invent or develop new ones
• Studying the theory and concepts that lie behind GIS
  and the other geographic information technologies
• Studying the societal context of geographic
  information
   – The legal context
   – Issues of privacy, confidentiality

   – Economics of geographic information
 Geographic information science
• The science behind the technology
   – Fundamental questions raised by the use of systems and
     technologies
   – The science needed to keep technology at the cutting edge
• A multidisciplinary field
• ’Spatial' or ’Geographic'?
   –   ’Geographic' has to do with the Earth
   –   ’Spatial' has to do with any multi-dimensional frame
   –   ’Geographic' is a subset of 'spatial'
   –   ’Geospatial' is sometimes used
An information system applied to
        geographic data
• System: a group of connected entities and
  activities which interact for a common
  purpose
• Information system: set of processes
  executed on raw data to produce information
  which will be useful in decision-making
• GIS: uses geographically referenced data as
  well as non-spatial data and includes
  operations which support spatial analysis
              Spatial data
• Objects or entities that are referenced
  by their location
  – Latitude / longitude coordinates
  – x / y coordinates
  – Street address
  – Administrative unit
            Attribute data
• Data that are linked to the spatial
  objects
  – Census data by administrative unit
  – Land parcel ownership records
  – Soil or vegetation characteristics
  – Health records by medical center
  – Road quality information
             Attribute relations
                                    Census districts

 302
                  305                              Id    Pop      HH
                                                   305   20,838   5,934
                                                   306   74,293   21,893
            304
303                           306                  ...   ...      ...

                                       Hospitals
  154             156
                                                   Id    Type     Staff
      155                                          156   RPH      17
                         157                       157   General 47
             158
159                                                ...   ...      ...
                        160
          List and Tables
Traditionally information is organized in lists,
maps add information about the “where” of the data
      Why is GIS important?
• Integrates spatial and other types of
  information
• Provides a consistent analysis framework for
  geographically referenced data
• Provides new and insightful ways of
  manipulating and displaying data
• Allows viewing and analysis of data based on
  geographical proximity and relationships
     Exploring Relationships
• Based on geographic location and
  proximity, GIS makes connections
  between activities
  – Looking at data geographically can often suggest
    new insights, explanations
  – These connections are often unrecognized
    without GIS, but can be vital to understanding and
    managing activities and resources
  – E.g., we can link pollution sources with disease
    patterns
      Combining data sets
                     l      l
                     ll
                      l l
                    l l                 l


                                    l
                                l
                                l   lll l
                                    l  l




Pollution Sources    Leukemia Cases
Information about “where” allows us to combine
           heterogeneous data sets



              l       l
              ll
               l l
             l l                  l


                              l
                          l
                          l   lll l
                              l  l
Space as an indexing system
    Rivers



    Settlements   +           +
                      +
                  +
                          +


    Admin.
    Units



    Reference
    Grid


                  Longitude
          Alternative Names
•   Geographic(al) Information System
•   Spatial Information System
•   Land Information System
•   Environmental Information System
•   Automated Mapping/Facilities Management
•   Geographical Information Sciences
•   Spatial Analysis
•   Desktop Mapping
GIS versus Desktop Mapping
• Desktop mapping emphasizes display
  and simple analysis of packaged data
  sets
• GIS provides the functions required to
  create, manipulate and integrate spatial
  databases as well as advanced analysis
  functions
GIS and other ISs
    Contributing disciplines and
           technologies
•   Geography        • Statistics
•   Cartography      • Operations
•   Remote Sensing     Research
•   Photogrammetry   • Computer Science
•   Surveying        • Mathematics
•   Geodesy          • Civil Engineering
            Application Areas
•   Utilities             • Natural Resources
•   Marketing               Management
                          • Ecology
•   Transportation
                          • Climatology
•   Urban / Cadastre
                          • Global change research
•   Health provision      • Oceanography
•   Epidemiology          • Famine early warning
•   Demography            • Navigation
•   Emergency response    • Agriculture
•   Social sciences and   • ……….
    humanities
                 Origins of GIS
• Advances in computing, cartography and
  photogrammetry --> automated GIS in 1960s
• Ian McHarg published “Design with Nature” in 1969
   – formalized concept of land suitability/capability analysis
• Harvard Laboratory for Computer Graphics
   – dev. & made avail. series of automated mapping & analysis
     prog.
• 1st GIS: Canada Geographic Information System
  (CGIS)
   – Roger Tomlinson, 1960s, rehabilitation & dev. of Canada’s
     agricultural lands
• 1970s commercial development -> ESRI, Erdas
          Origins of GIS
• Cartography: automated mapping, map
  algebra
• Remote sensing: raster image
  processing
• Computer science: database
  management systems
• Geography: spatial analysis
          What is a GIS?
• A system of hardware, software and
  procedures designed to support the
  capture, management, manipulation,
  analysis, modeling and display of
  spatially referenced data for solving
  complex planning, management and
  research problems
          GIS Capabilities
• Data capture/input:
  – Input data by digitizing, scanning, or direct
    coordinate entry
  – Edit data in the GIS to correct errors or add
    features
  – Label the spatial features so they can be
    identified (names or codes)
             GIS Capabilities
• Management:
  –   Link attribute data to spatial objects
  –   Link to external databases
  –   Make changes in existing databases
  –   Update database features
  –   Import and export from/to other GIS or DBMS
  –   Combine map sheets to create large databases
       match the edges of neighboring map sheets
          GIS Capabilities
• Manipulation:
  – Make maps from different sources
    compatible so that they can be drawn on
    top of each other
  – Transformation of coordinates
  – Projection change
            GIS Capabilities
• Analysis:
  – Query
     • Select features by their attributes: “find all
       districts with literacy rates < 60%”
     • Select features by geographic relationships:
       “find all family planning clinics within this
       district”
     • Combined attributes/geographic queries: “find
       all villages within 10km of a health facility that
       have high child mortality”
            GIS Capabilities
• Analysis (cont.):
  – Buffer: find all settlements that are more than
    10km from a health clinic
  – Point-in-polygon operations: identify for all villages
    into which vegetation zone they fall
  – Polygon overlay: combine administrative records
    with health district data
  – Geocoding/address matching: match an address
    list with a street map
  – Network operations: find the shortest route from
    village to hospital
          GIS Capabilities
• Modeling: identify or predict a process
  that has created or will create a certain
  spatial pattern
  – Diffusion: how is the epidemic spreading in
    the province?
  – Interaction: where do people migrate to?
  – What-if scenarios: if the dam is built, how
    many people will be displaced?
           GIS Capabilities
• Display/output:
  – Exploratory
     • visualize pattern and identify anomalies
     • compare information in map space and data
       space
  – Cartography
     • produce high quality map output for publication
     • create a digital or paper census atlas
  – Export map output to other packages
GIS in Planning and Policy Analysis
                   data collection

      Real World                     Data Sources

  take                                           data
 action                                          input


                                        Data
          Users
                                     Management

information
                                             data retrieval,
for decision         Analysis                manipulation
making
     Current State of the Art
• “High end”:
  – Integration of GIS and remote sensing
  – Interoperability (open GIS standards)
  – Advanced spatial analysis
  – Scientific visualization
  – Storing spatial data in generic DBMSs
     Current State of the Art
• “Low end”:
  – Desktop mapping “boom”
  – Commercial data providers
  – Global Positioning Systems (GPS)
  – Mapping add-ons to spreadsheets
  – Digital map libraries (on-line)
  – Access to spatial data via the Internet
Search
Zoom-in
Thematic mapping

				
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posted:10/19/2012
language:English
pages:45