GEM 3390

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Lecture 15 Content

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

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(No Transcript)
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• Choice of data structures
• Depends upon
• Intended use of data
• Accuracy of the intended GIS application
• Project cost of the intended GIS application
• Various algorithms exists to convert between data
  structures
• Vector to raster ? rasterization
• Raster to vector ? vectorization

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• Common database structure used to store and
  manage raster and vector data structures is the
  Relational Database Management System (RDBMS)
• Main function is to link the geometric
  representations to attributes
• Commercial RDBMS are INFO, ORACLE, INGRES,
  INFORMIX, DBaseIV, and so on

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• Topology
• RDBMS must be able to define the topology of
  geometric representations
• Topology is helps to define the geometric
  representation using the neighboring components
  of other geometric representations.
• That is, the RDBMS will be able to use
  information such as which polygon is to the right
  and left, and the from and to end points of
  lines

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• The georelational model have the following
  advantages
• Attribute data need not be stored directly with
  spatial database but can be access via a network
• Attribute data can be expanded, accessed,
  deleted, updated, without having to modify the
  spatial database
• Commercial RDBMS ensure that new developments are
  incorporated as a standard
• Data structures may be defined in standard ways
  using data dictionaries
• Keeping attribute data in RDBMS does not
  interfere with the GIS layers
• Attribute in RDBMS can be linked to spatial units
  that may be represented in a wide variety of ways

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• Types of RDBMS
• Arc-Node
• Most common and applied to vector data structure
• Each spatial unit has a unique ID
• Compact raster
• Makes use of sets of pixels which has unique IDs
• Used in the raster data structures

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• Quadtree RDBMS
• Allow data to be represented at various levels of
  spatial aggregation
• Discussed earlier lecture
• Object RDBMS
• Object oriented (OO) approach
• Geometric and attribute data are stored in
  relational tables
• OO programming provide the functionality to
  interface the data

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• Relational GIS

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• Object Oriented GIS

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• The End