Geog 495 Final Exam Review

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Geog 495Final Exam Review

• 11/23/05
• Final exam on 11/28/05 Mon

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Outlines

• I. Big picture
• Attribute
• Space
• Attribute Space
• II. Small picture
• GIS view on spatial data
• DBMS view on spatial data
• III. Synthesis

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I. Big picture

• Geographic information has three main components
  space, time, and attribute
• Traditionally the representation of attribute is
  well studied in contrast to space and time
• How attribute is represented in computer ?
  database model (first half of this course)
• How space is represented in computer ? spatial
  data model (second half of this course)
• How space is combined with attribute
• In GIS (GIS Architecture)
• In DBMS (SDBMS Architecture)
• Integration of GIS with DBMS

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Database model

• Hierarchical
• Network
• Relational
• Object-oriented
• Object-relational

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Spatial data model

• Object view
• Field view

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GIS architecture

• Hybrid
• Purely relational
• Object-oriented or object-relational

File-system into database system
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SDBMS architecture

• Purely relational
• Object-oriented
• Object-relational

Accommodated into spatial semantics
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Integrating GIS with SDBMS

• GIS-centered
• e.g. Arc/Info ODBC
• Whats the relative advantage of this approach?
• SDBMS-centered
• e.g. Oracle Spatial
• Whats the relative advantage of this approach?

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GIService

• Utilize specialized GIS functionalities that meet
  specific needs
• Built upon DBMS
• Somewhat eclectic good things from both

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II. Small picture

• Two views on spatial data model
• GIS view focused on how to store spatial
  information suited to application needs (e.g.
  building topology for routing applications)
• SDBMS view focused on how to store spatial
  information suited to SQL-like queries (e.g.
  defining spatial data type, spatial operators)

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1. GIS view on spatial data

• Data hierarchy
• Data model how spatial concepts are viewed
• Data structure how spatial information in stored
  in computer
• Data format how data structure is stored in s/w
  specific format

Human thinking
Level of abstraction
Machine code
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Data model

• There are two common views
• Object-view
• The world is composed of discrete entities
• Field-view
• The world is composed of continuous fields
• Both coexists in the real-world
• One phenomenon can be represented in two views
• Human perception tends to discretize information
  also

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Data structure

• Data structure that stores spatial information
• Vector composed of (a set of) point
• Raster composed of grid cell
• Data structure that stores attributes derived
  from spatial relationships
• TIN connected network of points whose attributes
  vary
• Matrix represent attributes based on a pair of
  spatial objects

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Do you know?

• Vertice, node, point, line, polygon, multishape
  polygon, multistring.
• Topology vs. spaghetti model
• Planar vs. non-planar
• Compression methods for raster data structure
• Run-length code
• Quadtree

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File format

• Different systems use different file formats
• Needs for interoperability
• How can we promote interoperability?
• Metadata
• Metadata standard?
• What kind of information is documented?
• FGDC standard

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Do you know?

• SDTS
• XML
• Open GIS
• Characteristics of specific file format and how
  they are classified into different data model?
• TIGER/Line
• DEM
• MrSID, BIL, GeoTiff (These are common DOQ format)

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2. DBMS view on spatial data

• Spatial data type
• Spatial operators

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Spatial data type

• Object
• Point sets
• Do you know OGIS spatial object types?
• Field
• Tessellation (grid) representation
• No too much work has been done

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Spatial operators

• On field-based data
• Local (e.g. , -,)
• Focal (e.g. gradient)
• Zonal (e.g. average)
• On object-based data
• Topological (e.g. within, overlap, touch)
• Metric (e.g. distance, direction, area)

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Miscellaneous

• What is spatial access method (or spatial
  indexing)?
• Quadtree vs. R tree
• Query processing
• Single scan vs. multi scan

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III. Synthesis

• More DBMS approach to GIS is desirable
• DB system is superior to file system
• DB gets increasingly smarter
• Distributed GIS environment gets increasingly
  popular

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• Inadequacy of RDB to representing spatial
  concepts should be accommodated
• User-defined spatial data types
• User-defined spatial operators
• Custom data model (refer to next week
  presentation on geodatabase case studies)
• Geographers role for formalizing spatial
  concepts (Naïve geography?)