This paper analyzes quantification error versus location error in a compari
son between two cellular maps that show a categorical variable. Quantificat
ion error occurs when the quantity of cells of a particular category in one
map is different from the quantity of cells of that category in the other
map. Location error occurs when the location of a category in one map is di
fferent from the location of that category in the other map. The standard K
appa index of agreement is usually not appropriate for map comparison. This
paper offers alternative statistics: (1) proportion correct with perfect a
bility to specify location, (2) proportion correct with perfect ability to
specify quantity, (3) Kappa for no ability (4) Kappa for location, and (5)
Kappa for quantity These statistics can help scientists improve classificat
ion. This paper applies these theoretical concepts to the validation of a l
and-use change model for the Ipswich Watershed in Massachusetts.