EXAMPLE ANALYSIS USING A RASTER GIS - o y if both 4 and 5...

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EXAMPLE ANALYSIS USING A RASTER GIS Objective identify areas suitable for logging an area is suitable if it satisfies the following criteria: o is Jackpine (Black Spruce are not valuable) o is well drained (poorly drained and waterlogged terrain cannot support equipment, logging causes unacceptable environmental damage) o is not within 500 m of a lake or watercourse (erosion may cause deterioration of water quality) Procedure recode layer 2 as follows, creating layer 4 o y if value 2 (Jackpine) o n if other value recode layer 3 as follows, creating layer 5 o y if value 2 (good) o n if other value spread the lake on layer 1 by one cell (500 m), creating layer 6 recode the spread lake on layer 6 as follows, creating layer 7 o n if in spread lake o y if not overlay layers 4 and 5 to obtain layer 8, coding as follows
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Unformatted text preview: o y if both 4 and 5 are y o n otherwise • overlay layers 7 and 8 to obtain layer 9, coding as follows o y if both 7 and 8 are y o n otherwise Result • the loggable cells are y on layer 9 Operations used o recode o overlay o spread • we could have achieved the same result using the operations in other sequences, or by combining recode and overlay operations o e.g. overlay layers 2 and 3, coding as follows y if layer 2 is 2 and layer 3 is 2, n otherwise this would replace two recodes and an overlay o e.g. some systems allow layers to be overlaid 3 or more at a time • the names given to operations vary from system to system, but most of the operations themselves are common across systems...
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