Supporting Resources

for Lecture 12: Buffers and Distance Calculations

Index of Resources:

• Examples of applications using buffers heavily
• Constructing buffers from vector objects
• Calculating distance measurements in a raster
• Extended Voronoi Network

Siting criteria for landfills in Illinois counties

uses exclusionary logic mostly with buffers: 5 separate studies, each with slightly different criteria - which criteria reflect the best interests of the environment? the public?

CRITERIA \  COUNTIES
                      Crawford   Lake    Will Champaign Whiteside
100 year floodplain       X       X       X       X      7920
Wetlands                  X       X       X       X      5820
Airports (turbojet)   10000   10000   10000   10000     10000
Historic sites         1000     200       X       -      1320
Endangered species      500       X       X       X         X
Developed areas        1500     500       -       -         -
`Committed' devel.     1500     500       -       -         -
Geologic material type    -       X       -       X         -
Surface waters         1000     600       -     500         -
Public water supply    2500     500     500    1000      5280
Other water wells         -       -       -     200         -
Oil wells               250       -       -       -         -
Incorporated areas        -       -       X    7920      1320
Rural dwellings           -       -       -       -      1320
Cemeteries              500       -       -       X      5820
Schools               10000     500     500    7920      5820
Hospitals             10000     500     500       -         -

Source: Lindquist (1991) GeoInfoSystems Table 1, selected for key differences.

X denotes simple exclusion; figures are buffer distances in feet;
- indicates criterion not used in that county.

Construction of Buffers from Vector Objects

Distance Measurement in a Raster:

Extended Voronoi Diagrams

Extended Voronoi Diagrams can permit a non-contour approach for vector data
(compute zones belonging to nearest neighbors for points and lines)

Example of Extended Voronoi regions

THEN you can get ANY buffer distance by 'contouring' the extended neighborhood diagram:

Illustrations of Extended Voronoi courtesy of Chris Gold, University of Laval, used by permission of author.

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Version of 23 October 2003