Chapter 10: Vector Data Analysis

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Chapter 10Vector Data Analysis
Union Overlay

• Paul Sutton
• psutton_at_du.edu
• Department of Geography
• University of Denver

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Vector Operations

• Buffering and its Applications
• 2) Map Overlay (Union Intersect)
• 3) Distance Measuring Tools
• 4) Map Manipulation

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Buffers

• A buffer, in spatial information systems, is a
  polygon enclosing an area within specified
  distance from a point, line, or polygon.
• Buffers can be applied to a variety of
  applications such as transportation, forestry,
  environmental control and resource management.
  Listed below are some examples of real-world use
  
• 1) protected zone around lakes and streams
  
• 2) zone of noise pollution around highways
  
• 3) service zone around bus route (e.g. 200
  metres walking distance)
• 4) groundwater pollution zone around waste
  site

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Buffers are performed in Raster Vector
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Buffers can be 1 or 2 sided and of variable width
based on a feature attribute
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An example of a Buffer Analysis

• Suppose the state of Colorado imposes the
  following rules for available logging locations
• No logging within 10 km of Highways
• Must log within 5 km of Forest Service Roads
• Also, Logging Companies do not want to log above
  3200 meters (too much snow)
• Data needed DEM, Highways, Forest Service Roads

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Visualizing the Analysis
10 km Buffer of Highways Roads (suitable area
must be outside)
5 km buffer of Forest Service Roads (Suitable
area must be INSIDE)
Areas that are too high In Elevation (over 3200
meters)
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What the Final Answer Looks Like
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Detail of Final Answer
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Map Overlay

• Point In Polygon Points can be given attributes
  of the polygon they fall in. OrPoints can be
  counted per polygon.
• Line in Polygon Lines get broken whenever they
  cross polygon boundaries. May be useful for
  identifying the underlying soils of a road
  network.
• Polygon on Polygon Union Intersect

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A simple Point in Polygon Problem

• Below is an image of the conterminous U.S. and
  the Ozone Monitoring locations.
• How many monitors in each state?
• Which state has highest sites/area?
• Which State has highest sites/person?

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How is this done?

• 1) Perform a Spatial Join. Join the PAT of the
  states to the PAT of the Points using Shape.
• 2) Summarize the Joined Table
• 3) Join that table back to the PAT
• of the states coverage.
• 4) Edit This table to create fields
• and calculate

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Sites Per Person
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Sites Per Area
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Polygon on Polygon Overlay
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Example Intersecting two Polygon Coverages
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Map ManipulationsDissolve, Merge, and Clip
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ExampleWhat is the Dissolve Function?

• Suppose you convert a U.S. Counties Coverage to
  a U.S. States Coverage.
• What happens to the Tabular attributes?
• What Happens to the Attribute Values?

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Dissolve..Think about the Tables Fields
What happens to the following fields and their
Values? Shape, Name, State, State FIPSCnty Fips,
Area, Pop 1990, Pop 90 / sq mile, Households,
Males, Females, White, Black, Asian, Hispanic,
Age_Under 5?
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Distance Measurement

• Measuring Distance is often an important analysis
  method in Spatial Studies.
• Typically distance is measured from Points to
  other points (e.g. Elvis sightings and Bars) or
  Points to Arcs (e.g. Gas stations to freeways)
• These kinds of measures used in Spatial
  Interaction Models, Migration Studies, and
  Business/Marketing Applications
• ArcView does this with the Spatial Join

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The Spatial Join

• Use Assign data by location when you want to use
  a spatial relationship to join data from the
  attribute table of one theme to the attribute
  table of another theme. Depending on the type of
  data you have, the join will be one of three
  types of spatial relationships 'nearest',
  'inside', or 'part of'.

Note I think the colors are wrong
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Example of Spatial Join for a Point Line
Application

• How far are each of these points (ozone
  monitoring locations) to the nearest highway