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I'm currently analyzing the change detection for urban expansion over a decade starting from 2006-2016. How can I use raster calculator in order to know the changes? For example, from agriculture to urban area and etc. I already classified the images into 4 classes, urban area,vegetation,water bodies and barren land.

  • What software are you using? – Fezter Nov 30 '16 at 5:46
  • What's your goal? To identify where there were changes, or to be able to discern from a single output what the particular changes were? – J Kelly Dec 29 '16 at 1:45
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Try reclassifying the rasters to a different scale of numbers, such as

urban = 1
ag = 10
forest = 100
water = 1000

Then just subtract the rasters in Raster Calculator:

0 will mean unchanged.
9 will mean ag --> urban
-9 will mean urban --> ag
99 will mean forest --> urban
90 will mean forest --> ag
-99 will mean urban --> forest etc.

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