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Unformatted text preview: some systems allow a full range of mathematical operations o e.g. newvalue = (2*oldvalue + 3)2 Overlaying layers an overlay occurs when the output value depends on two or more input layers o many systems restrict overlay to two input layers only examples: 1. output value equals arithmetic average of input values 2. output value equals the greatest (or least) of the input values 3. layers can be combined using arithmetic operations o x and y are the input layers, z is the output o some examples: z = x + y z = xy z = x / y 4. combination using logical conditions o e.g. if y>0, then z = y , otherwise z = x o note: in many raster packages logical conditions cannot be done directly from input layers must first create reclassified input images so that cells have 0 if they do not meet the condition and 1 if they do 5. assign a new value to every unique combination of input values o e.g.LAYER 1 LAYER 2 OUTPUT LAYER 1 A 1 1 B 2 2 A 3 2 B 4...
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This note was uploaded on 12/04/2011 for the course GEB 1011 taught by Professor Staff during the Fall '08 term at Broward College.
 Fall '08
 Staff

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