GIS ' Lecture 12

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Lecture 12 Content

• Geographic Information Systems (GIS)
• Data Structures and Data Management
• (Continued)

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(No Transcript)
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• All GIS are computer representations of some
  phenomena of the real world
• GIS present a simplified view of the world as it
  would be impossible to represent reality in its
  entirety in a computer because of the multitude
  of data is unlimited and the limitations posted
  on the computer hardware for storage and
  processing speeds
• Two considerations are data sets and computer
  hardware

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• Data and information
• Raw data sets are observations made from the real
  world
• Raw data sets are collected as facts or evidence
  that can processed to give meaning to the
  phenomena and convert the data into information
• Therefore, there is a clear distinction between
  data and information, although the two terms are
  used interchangeably
• Derived data sets are processed raw data which
  can also be considered as information (eg.
  Population density)

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• Data can be thought as being raw numbers
• To make the numbers useful, then a context need
  to be added
• To interpret the tables, maps, and charts use is
  made of a unit of measurement that is related to
  the raw data (eg. Population per square km)
• With these details the data becomes information

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• All data sets have three modes of dimensions
  which are temporal, thematic, and spatial
• For example a given data set
• Temporal mode 14th February 1995 (Time stamp)
• Thematic mode attributes from an avalanche
  accident (Attribute data)
• Spatial mode location of Three pines valley
  (Spatial data)

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• Maps
• Traditional method for storing, analyzing and
  presenting spatial data is the map
• A map is a picture, and a picture tells a
  thousand words
• Maps take many different forms and come at a
  range of scales
• Maps range from sketches to the more complex
  topographic and thematic maps

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• A sample of map types
• Thematic maps show data relating to a particular
  theme or topic, such as soil, geology, land use,
  population, or transport
• Topographic maps contain a diverse set of data on
  different themes such as land use, relief, and
  cultural features may all appear on the same
  topographic map
• Dot Maps Identify the location of surveyed
  points or events
• Grid Maps Grid maps are made up of a regular
  grid of squares the color of each square
  representing the area's value

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• Mapping process considerations
• Establish the purpose of the map
• Define the scale of the map
• Select features to be portrayed
• Choose the representation of features (point
  line, polygons)
• Generalize the features for representation in 2D
• Select a map projection and coordinate reference
  system
• Annotate the map with keys, legends, north arrow
  and text

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Effects of scale related to generalizing
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• Basic cartographic primitives

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• The End