23 Indexation and Weighting Details

The indexation function belongs to the category of connection functions. This connection function calculates an additive weighted index or a gemetric weighted index from the selected files according to the formula:
Additive Weighted Index:

I =   wi ⋅xi = w1 ⋅x1 + w2 ⋅x2 + w3 ⋅x3 + w4 ⋅x4 + ...+ wn ⋅xn

Geometric Weighted Index:

   ∏n  wi    w1  w2  w3
I =   xi  = x1 ⋅x2 ⋅x3

It is also possible to apply inverse weighting. If you select inverse weighting a negative sign will be set in front of your weighting. If you apply normalization prior indexation we suggest to use inverse normalization instead. Furthermore it is possible to set thresholds. The additive weighted index alows compensation of negative performance in one indicator by rating high in another. The geometric weighted index option makes this more difficult. If a pixel rates for example 0 for one indicator it won’t acchieve a higher score than 0 with the geometric aggregation method. If it is better to calculate an additive or a geometric weighted index depends on the specific index you want to calculate and if compensation is desired or not.