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Introduction to


GIS packages store spatial data in two basic forms: Vector and Raster ... Raster GIS data structures are preferred for digital elevation modelling, ... – PowerPoint PPT presentation

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Title: Introduction to

Introduction to Geographic Information Systems
Geographic Information Systems are computer
systems for the
Capture Storage Retrieval Analysis Display
of Spatial Information
Spatial Information
Everything on the Earth's Surface has a location
Geographic Information may be referenced by
Latitude and Longitude Metric Coordinates
(AMG) Street Address Parcel (property
boundaries) Spatial relationship to other map data
Maps in Geographic Information Systemsare
represented thematically
Map data is separated into THEMES or OVERLAYS of
discrete information. Hydrologic data is mapped
on a separate overlay from soils or geology.
Geographic Information Systems are
sometimes referred to as Thematic Mapping Systems
or Map Overlay Systems
Mapped themes
Spatial Query
  • The organisation of mapped data by themes allows
    flexible and powerful methods of searching mapped
    data for specific combinations of factors.
  • "Locate and Display all playgrounds downstream of
    landfills within 100 year floodplain"

Query by Attribute
  • GIS systems link mapped data to tabular (text)
    data bases. This allows one to query by
    attributes in the database and have the GIS
    display their location as a map.
  • "Display all water mains installed before 1950
    with a diameter less than 12 inches"

Corresponding map feature
Attribute table
Spatial Information
  • In addition to organising spatial data by themes,
    mapped information is also structured as points,
    lines and polygons.

Point Data
  • Examples of point data include location of wells,
    post office, man holes, stream gauges, bird
    nesting sites or control points.

Nesting Sites
Line Data
  • Examples of line data include road networks,
    utility lines, stream drainages, and fault lines.

Stream Drainage
Polygon Data
  • Examples of polygon data include land use,
    vegetation cover, enumeration districts, soil
    types, and zoning.

Land Use
GIS packages store spatial data in two basic
forms Vector and Raster
GIS Data Structures Vector
  • GIS systems which store map features in vector
    format store points, lines and polygons with
    high accuracy. They are preferred in urban
    applications where legal boundaries and the
    analysis of networks are important.

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GIS Data Structures Raster or Grid
  • GIS systems which store map features in raster or
    grid format generalise the location of features
    to a regular matrix of cells. Raster GIS data
    structures are preferred for digital elevation
    modelling, statistical analysis, remotely sensed
    data, simulation modelling and natural resource

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GIS Data Integration
  • Many GIS systems handle both vector and raster
    data from a wide variety of sources including
    satellite imagery, cadastral information, hand
    digitised maps and scanned images.

Vector to Raster Conversion
The quality of the result depends on the chosen
cell size
  • In order to ensure that all maps in a GIS
    database overlay accurately, the data set is
    "geo-referenced" to a common coordinate system.
    In Australia the Australian Metric Grid is used
    to geo-reference all map data bases.

Setting Technical Standards
  • By setting technical standards for
    geo-referencing, data may be shared by different
    organisations producing GIS data bases.

Spatial Analysis
  • Spatial Analysis is a set of analytical
    procedures applied to GIS data to describe,
    predict, or assess environmental or social

Spatial Analysis Techniques
  • Spatial analysis techniques include methods for
  • Measuring Distance, and Area
  • Interpolating values
  • Reclassifying Map Features
  • Identifying the co-occurence of values on
    different map themes (overlay analysis)

Digital Elevation Modelling (DEM)
  • There are also specific methods for analysing
    terrain including
  • Calculating slope
  • Solar aspect
  • Viewshed Analysis
  • Runoff Analysis

Automated Cartography and Data Visualisation
  • GIS systems also have reasonably sophisticated
    graphic capabilities for map production and data
    visualisation in plan and perspective.

GIS Applications
  • Because GIS systems are designed as a generic
    system for handling any kind of spatial data,
    they are applied in a wide range of applications
    in urban and rural environments.

Urban GIS Applications - Utilities
  • Utilities management - Water, gas, electricity,
  • Flow demand/analysis - Hydrologic performance of
    utility networks
  • Storm water management - Modelling
    surface/subsurface flows, effects of
    retention/detention basins on peak flows

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Urban GIS Applications - Health and Safety
  • Building Codes - Permit Information, code
    enforcement, permit processing, building
  • Emergency Services Planning - Location and
    allocation of critical facilities, hazardous
    materials mapping, risk management, flood
    control, evacuation routes, fire incident
    analysis, emergency response analysis
  • Health Services - Patient distribution analysis,
    water quality monitoring, disease outbreak
    patterns, medical facilities planning

Urban GIS Applications - Health and Safety
  • Police Services - Crime pattern analysis,
    computer-aided dispatch, response time analysis,
    resource allocation
  • Sanitation - Waste collection routing/balancing,
    solid landfill site selection, hazardous waste
    disposal siting.
  • Transportation - Traffic incident analysis,
    parking facilities planning, route analysis, road
    maintenance scheduling, traffic engineering,
    traffic zone analysis, traffic management, road
    improvements planning, bus routing/scheduling,
    car pooling services

Urban GIS Applications - Planning
  • Land Use Analysis - Land Use Suitability, Land
    Use mix, area analysis
  • Strategic Planning - Land Use trends analysis,
    population projections/distribution, land
    availability, land rent.
  • Zoning - Conformance, performance analysis

Natural Resource GIS Applications
  • Agricultural Planning/Conservation - Agricultural
    capability analysis, market analysis, whole farm
  • Forestry - Timber assessment and management,
    Harvest scheduling and planning, environmental
    impact assessment, pest management
  • Wildlife - Habitat assessment and management,
    identification of rare/endangered species and
    habitats, impact assessment

Natural Resource GIS Applications
  • Catchment Management - Runoff and erosion
    modelling, sedimentation and water quality
    studies, evaluation of management alternatives,
    integrated catchment management.
  • Archaeological Site Conservation - Mapping and
    prediction of prehistoric sites, site vandalism
    studies, site management studies.
  • Geology and Mining - Oil, gas and minerals
    exploration. Geologic mapping and terrain
    analysis, open pit mine design and reclamation,
    geologic hazard mapping
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