Geographic%20Information%20Systems

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Geographic Information Systems

• GIS Analysis and Modeling

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5. (9) Spread Functions

• An evaluation of phenomena that accumulate with
  distance
• It calculates the running total of a variable at
  each step when moving outwards at all directions
  from one ore more starting points, and writes the
  running total to an accumulation file
• Friction surface or Terrain trafficability

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• The calculation of distance using a spread
  function

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• The calculation of distance with barriers

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• Generation of a travel-time data layer

• Land use data layer

• Friction surface

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• Travel time calculation

Friction surface data layer
Start pointdata layer
Cumulative travel time data layer
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• Travel-time analysis procedure
• - A spread function is used to calculate a
  travel-time map from the friction surface and the
  start points

Friction surface data layer

• Start points data layer

• Travel time map

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Least-Cost Analysis Path 2
Distance between stops Athens to
Lathouriza About 25km or 15.5mi Lathouriza to
ThorikosAbout 36km or 22mi Thorikos to
Sounion13km or 8mi Total 74km or 45.5mi
From Erin Warford ..
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5. (10) Stream Functions

• The stream function (also termed a seek function)
  performs a directed search outward, step by step,
  from a starting point based on a set of decision
  rules. The procedure stops when the rules are
  violated
• The output is a trace of paths

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5. (10) Stream Functions

• Applications use of a seek function to model
  flow path

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Stream Functions

• Application find path through a sewer system
  from point A to point B

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Stream Functions

• Application delineate watershed boundaries

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5. (10) Viewshed Analysis

• The concept of viewshed the delineation of areas
  that are viewable from a point

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5. (10) Viewshed Analysis

• Data sources for viewshed analysis

Topography
Surface feature locations heights of
obstructions
Viewer positions
Targets (optional)
Viewshed map showing areas visible from one or
more viewing positions. Shaded areas are hidden
from view
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5. (10) Viewshed Analysis

• Viewing parameters
• - Maximum viewable line-of-sight distance
• - Location of viewing point
• - Vertical and horizontal angle of view
• - Viewing direction

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• Viewing parameters

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Viewshed
The above maps show the results of analyses
around Saddleback (left) and Old Blue (right)
mountains. On the maps, green areas are visible
from the location cited (shown in yellow), while
gray areas are obstructed from view. The
Appalachian Trail is shown in red. http//www.nort
hgeo.com/services/carto/projects/LURCViewshed.htm
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• scenic lookouts

M. Dolce, Buffalo State College
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From Erin Warford
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Viewshed
esri
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5. (11) Illumination and Perspective View

• Illumination
• - Mimic the effect of shining a light onto a 3-D
  surface
• - Create a shaded relief image
• - Illumination source has a
• defined position relative
• to the surface

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5. (11) Illumination and Perspective View

• Perspective view
• - Creates a 3-D block diagram showing how surface
  appears from a defined position
• - Is useful in showing the 3-D context of
  features on a surface, such as a natural landscape

http//www.sdsmt.edu/online-courses/geology/mprice
/geo416/lecture9.ppt
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3-D Perspective
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Z10
J. Yan, SUNY Buffalo
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J. Yan, SUNY Buffalo
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A. Toy, SUNY BUffalo
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2. (4) TINs

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Color infrared composite of the IKONOS draped
over the DEM as viewed from the west side of the
study area to the east from an elevation of
10,000 m, Xichang, ChinaXu, University of Utah,
Gong, UC-Berkeley
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Readings

• Chapter 5,6,9,10

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5. (11) Illumination and Perspective View
GIS can combine map types and display them in
realistic three-dimensional perspective views
that convey information more effectively and to
wider audiences than traditional, two-dimensional
maps.