OVERLAY

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OVERLAY
OVERLAY
Now we get into more complex modeling!
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And now will take up

• COVER
• APPLYING BOOLEAN LOGIC
• SOME EXAMPLES OF NON-BOOLEAN PROBLEM SOLVING

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Cover

• NOT available in the modeler but is in the
  calculator
• It is essentially an UPDATE tool.
• An img with a window of zero value is placed
  over another img.
• The data under the window comes through and into
  the resulting file WITH the stuff outside the
  window

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Cover
1
0
Unacceptable areas in Black
over
When slope overlaid on perc rate get combined
unacceptable areas BECAUSE 1s in perc rate came
thru the window of 0s in slope image
get
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Cover
First covers second
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What is COVER used for!

• For finding areas acceptable or unacceptable
• For UPDATING an image.
• Something has changed and you need to edit part
  of your image
• make a binary mask (zero where new data goes)
• multiply times old data
• OVERLAY this image on top of new data
• This is basically the hard way to do it

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The process
MAKE WINDOW
X OLD DATA

COVER
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Booleans

• We have covered the use of Boolean images to do
  things like site selection using
• AND, OR, XOR, NOT
• That is not the only way to do things!
• Here are some alternatives

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ADD the Booleans

• In what way is the addition of the 4 binary
  levels better for decision making?
• In what way is it not so good?

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How is this better?
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How is this better?
111 area where all 3 criteria are good 101 AOK
SOK criteria are good
111
101
110
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A Decimal System for Coding

• Our Ski Slope Example
• 1. Number of cells that simultaneously meet my
  criteria.
• 2. Prefer Steep slopes
• 3. Prefer Forested landuse over Forest403

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Prioritization again

• Locating building sites
• View of water
• Slope preference
• Road preference

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Possible combinations
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More possible combinations
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Always Boolean

• NO
• Here are two non Boolean models

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Example 1

• Lands best suited for making Growing coffee
  beans
• Work from bottom up
• Notice that the units for each map work ( if they
  dont you have a problem!)

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COFFEE
Not every thing is Boolean!
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COFFEE
Not every thing is Boolean!
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COFFEE
Not every thing is Boolean!
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COFFEE
Not every thing is Boolean!
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COFFEE
Not everything is Boolean!
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CORN

• Different technique to select the best areas to
  grow corn

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Example 2

• Find the best place to grow corn
• Start from middle this time
• Note that this analysis is all based on CLASSED
  data

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CORN
Another non-Boolean idea.
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CORN
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CORN
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CORN
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CORN
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CORN
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Summary

• Cover is a very useful function when you need it
• But it is not available in the modeler
• Only in Calculator and Overlay
• You dont always have to use logic functions with
  Booleans!
• Booleans are not the solution to all problems!

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Review of Exercise 6

• Part 1 is similar to Ex53
• Have to use Extract and Assign
• Coding for ranking