Geographic Information Systems GIS

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Geographic Information Systems (GIS)

• 451-102Introduction to Surveying (BPD)

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Two hours of GIS, hmm!

• Spatial data
• Options for analysis
• GIS History 101
• Not just software?
• Representing the real world
• Applications
• Queries and capabilities

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Spatial data

• The key data type in GIS
• Thematic data layers with location
• Examples
• Many ways to obtain spatial data
• Maps used to show spatial data
• Colours or symbols for attributes

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Basic analysis options

• We get spatial data, then what?
• Questions GIS can answer
• Those related to proximity
• Those related to size/dimensions
• Scenario to discuss
• Properties and their type/value
• Utilities networks (e.g. roads, water)

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Definition of GIS

• Database of spatial data
• Represent real world using objects
• Have location and attributes
• Spatial data layers overlay them
• Store, retrieve, analyse and display
• Common reference system needed

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The development of GIS

• Thematic maps for many years
• Combining thematic maps
• Use of transparent overlays
• Computers and cartography
• Mapping technology developed
• Software development

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More than software

• GIS encompasses many things
• Hardware
• Data
• Analysis methods
• Application areas
• People

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Representing the real world

• Two major methods
• As occupied by discrete objects
• As a continuous field
• Vectors and rasters
• Method controls analysis options
• Change representations? messy

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Vectors

• Point coordinates
• Traffic lights
• Lines set of coordinates
• Road networks
• Polygon set of coordinates
• Zoning areas

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Vectors

• Attributes associated with objects
• Have many attributes
• GIS maintains object relationships
• Examples of analysis
• Perfect for roads, boundaries
• But what about for terrain?

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Rasters (continuous fields)

• Simplest conceptual model
• Defined as a regular grid of cells
• Assigns values everywhere in field

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Comparison of models

• Vector advantages
• Good for artificial features
• Accurate, multiple attributes
• Vector disadvantages
• Complex structures, more expensive
• Combining overlays is messy
• Scale of data is not obvious

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Comparison of models

• Raster advantages
• Simple structure, reliable overlaying
• Affordable, simpler spatial analysis
• Scale is visible in the data
• Raster disadvantages
• Store redundant data, generalised
• Layers can only have one attribute

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Summary quiz

• Explain 1 thing about spatial data
• List 1 question GIS could answer
• Describe 1 aspect of GIS
• Choose a real world object and tell how you would
  represent it in GIS