Compare cell values of different raster layers

Discussion created by berquinn on Jul 26, 2013
Latest reply on Jul 30, 2013 by TKONG
I want to look at the impact of varying weight values in a weighted overlay analysis (it???s part of a study on the impact of uncertainty in weights on the resulting maps when using weighted overlay analysis to find suitable sites for development). I have 13 different sets of weights which sum to 100 and 13 maps, each prepared with a different set of the 13 weights. The first map using the values 65 + 28 + 7 is my base map and all other maps are a variation of the base map values. For example one map uses the values 59 + 33 + 8, another uses 69 + 24 + 7, another uses 71 + 22 + 7 and so on.
My resulting maps have cells with values between 1 and 9 with cells of value 9 being the most suitable locations for development.
For each of my maps I want to compare the total number of cells with a value of 9 against that of my base map - so I want to
compare the base map against each of the 12 other maps and look at whether and to what extent the amount and location of cells
with value 9 changes. (I want to find out to what extent uncertainty in the input weights influences the output of the weighted
overlay analysis).
Any suggestions of a suitable method to carry out this analysis would be appreciated. I have been using raster calculator to subtract each of the variation maps from the base map but I want to focus just on difference in the most suitable cells (i.e. those with a value of 9) and the raster calculator doesn???t seem to be a very efficient way of doing this.

Many thanks