I have used Supervised Classification (Maximum Liklihood) to produce thematic maps from Landsat imagery in ArcMap for the years 2004, 2006, 2009, 2013, 2015. I have produced 9 land-use classes. I now want to examine 'from to' change between years, but the class values in each map vary.

How do I get the class values to correspond in each of the maps?

1 Answer 1


You need to use Con() function in raster calculator to change the cell values of each class to the corresponding cell values of the correct class.

However, since the order of the 9 classes are different in each image, you need first to change the cell values to a scale not in the range of 1-9, but to some unique number for each class.

Why you need to do this is because if ,for example, the class 1 should be class 3, and class 3 should be class 1, if you wrote con("raster2004"=1,3,"raster2004") in raster calculator, you will change the pixel value 1 to 3, but when you need to correct the pixel value 3 to 1 using the same method con("raster2004"=3,1,"raster2004"), this time the class 3 includes also class 1 (two classes). That is why you need to convert the pixel values to a scale not in the range 1-9 to avoid merging classes by mistake.

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