Overview of EX5 AND Some Boolean Logic

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Overview of EX5ANDSome Boolean Logic

• OR
• Some hints on how to stay out of trouble

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Whats Boolean processing

• Its using Boolean Logic to solve problems

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Truth Tables
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MULTIPLE OPERATIONS

• If you AND multiple images you get only the areas
  where 1 appears in ALL layers!
• If you OR multiple images you get only the areas
  where 1 appears in more than one image
• If you XOR multiple images you get only the areas
  where only 1 layer has 1s.

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Boolean Site Selection

• Make BOOLEAN images of acceptable areas
• AND them all together using CALCULATOR or in a
  Model
• Result is a BOOLEAN image of OK areas
• ADD them all together using CALCULATOR or in a
  Model
• What is result if, for example you have 4 such
  images?
• 0 where unacceptable, 1,2,3, or 4 where
  acceptable
• A side benefit - now you know how many factors
  were in the acceptable areas -- 4 has got to be
  good!
• Sometimes one method is better than another!

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LOGIC
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AND Acceptable areas
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OR Acceptable areas
AOK OR SOK OR EOK OR WOK
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XOR Acceptable areas
AOK XOR SOK XOR EOK XOR WOK
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Order make a difference?

• Can! so use parenthesis to separate logic
  statements

AOK XOR EOK XOR SOK
AOK XOR SOK XOR EOK
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Logical combinations
AOK AND ( SOK OR EOK)
(AOK AND SOK ) OR EOK
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An Example of trouble

• A is 1 where topsoil is clay loam,
• B is 1 where soil pH gt 7.0, and
• C is 1 where soil is poorly drained
• (A AND B) OR C is 1 where (topsoil is clay loam
  AND pHgt7.0) OR the soil is poorly drained
• A AND (B OR C) is 1 where topsoil is clay loam
  AND (pHgt7 OR soil is poorly drained)

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Using Boolean Logic is not the only way!
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What about ADDing booleans

• In what way is the addition of the 4 binary
  levels better for decision making?
• 1 means ONLY 1 of the constraints was good
• 4 means all for were (best choice?)

AOK SOK EOK WOK
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Another method

• Use binary values in the images
• 1, 2, 4, 16 ..
• Possible values are
• 14 5
• 124 7
• 2 16 18
• Max value is 12416 23
• The combinations are unique

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How is this better?
AOK EOK10SOK100
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How is this better?

• 111 area where all 3 criteria are good
• 101 AOK SOK criteria are good
• 11 AOK EOK are good

111
101
110
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How is this better?

• 111 area where all 3 criteria are good
• 101 AOK SOK criteria are good
• 11 AOK EOK are good

As long as you are using booleans this will work
because the only possible values for each binary
are 1 and 0. Thus the image can only have the
values 1, 10, 11, 100, 110, and 111 You can tell
at a glance what is good and what is not in one
image!
111
101
110
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Summary

• Applying Boolean logic is the most efficient way
  to do site selection types of processing
• But be careful that you do it correctly
• Estimate what the image should look like
• Check it
• Keep Boolean processing simple one step at a
  time until you get better at it.
• But remember that Boolean Logic is not the Only
  way!

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OVERLAY

• With the addition of the CALCULATOR to IDRISI the
  OVERLAY function becomes less important
• But it is still a valuable tool.
• So what does it do?

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Overlay Dialog
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Cover

• It is essentially an UPDATE tool.
• An image with a window of zero value is placed
  over another image.
• 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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2 Problem Solutions

• Finding the best place to grow coffee
• Finding the best place to grow corn
• Very different processes used

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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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Example 1
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Example 2

• This one is really different
• 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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In the Modeler

• Boolean operators
• AND is AB
• OR is AB, relcass 2 to 1
• XOR is AB, reclass 1 to 0, 2 to 1
• NOT is reclass 1 to 0, 0 to 1
• How to make sub-modules

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Sub Models

• Make a Model that does something like do an XOR
  of two Boolean images

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Sub Models

• Make a Model that does something like do an XOR
  of two Boolean images

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Sub Model 2

• Save the model
• THEN save it as a sub-model
• You get this modal dialog

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Sub Model 2

• Save the model
• THEN save it as a sub-model
• You get this modal dialog

CLICK OK!
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Apply the Sub-Model

• Make a model and insert the sub-model

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A Demo works better!