Its the Geography, Cupid

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Its the Geography, Cupid!
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GTECH 201

• Lecture 04Introductionto Spatial Data

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Todays Content

• Types of spatial data
• World models
• Spatial data models
• Spatial data structures
• The geo-relational principle

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Types of Spatial Data

• Locations or regions
• Relative positions
• Points, lines, or areas
• Regular vs. irregular
• Continuous vs. discrete

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Geostatistical Data aka random field data

• Measurements taken at fixed locations
• Spatially continuous
• Small-scale variation
• Toblers Law of Geography

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Lattice Data

• Regular lattice
• Satellite image

• Irregular lattice
• Polygon map

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Spatial Point Patterns

• Distribution of locations
• e.g., bald eagles or earth quakes

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Why do we Need Models?
It wont fit!
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(No Transcript)
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Vector View
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Raster / Image View
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What is where? versus Where is what?

• What is where? Vector
• space is occupied by objects that are
  described by their attributes
• Where is what? Raster
• variation of an attribute as a continuous field

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Raster Vector

• Each world view presents different aspects of the
  real world
• Thus we can
• ask different questions (e.g. apply different
  operations)
• get different answers (e.g. apply different
  analytical tools)
• .. so choose carefully

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Raster Vector continued

• Converting between the raster and vector data
  models results in error

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Chrismans Spheres
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ANSI-SPARC Model for Software Development
GIS are systems to model the world User Model
Conceptual Model
Operational

Model
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GIS are Systems to Model the World
User Model how we intuitively think
Conceptual Model
Operational

Model ANSI-SPARC Model for software
development
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GIS are Systems to Model the World
User Model Conceptual
Model
Operational
Model ANSI-SPARC Model
for software development
how we systematically define ideas
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GIS are Systems to Model the World
User Model Conceptual
Model
Operational
Model
how we fuse systematic thinking into a
technologically defined context
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The ANSI/SPARC Model and Chrismans Spheres
application disciplines
geoinformation theory
computer science
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Digital Maps as Models
Representing a complex reality Continuous
variation Spatial Data spatial, temporal and
thematic Data Models
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What sort of Models are These?

• Raster Model - The world as regular tessellations
  defined by areal property
• Vector Model - The world as points, lines, areas
  and attributes.. making objects
• Object Model - The world as interacting entities
  with spatial dimensions

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Vector Data Models

• Spaghetti model
• Topological models

A file of spatial data that is a just a
collection of co-ordinate strings. Each entity
(or piece of spaghetti) is represented by one
data entry. There is no topology.
Topology refers to the spatial relationships
between objects. The topological model
represents spatial relationships such as -
length - area - connectivity - contiguity
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Raster Models
Pros Simple, computer friendly,
scanner friendly, field- friendly,
compressible Cons Large, unstructured,
inflexible
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Vector Models
Pros Structure, cognitive consonance(!),
compactness(?), accuracy Cons Inflexibility,
complexity, spuriously precise(?),
atemporal
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Object-centered Models
Pros Structure, power, potential
process links, consistency(?) Cons Extreme
complexity, power hungry
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Data Structure
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Attributes
Forest Inventory
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Geo-Relational Principle
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Database Relations
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Further Reading
ANSI/SPARC model Laurini Thompson. Fundamentals
of GIS, p.357-362 Chrismans Spheres Chrisman, N.
1997. Exploring Geographic Information
Systems Key Text for Concepts De Mers, M. 2004.
Fundamentals of Geographic Information
Systems. NY John Wiley Sons