Since each row corresponds to a summation surface, we apply the row normalization to imaging operators implemented as (sum) pull operators. We solve the normalized system:
The solution in equ-mod is equivalent to applying the imaging operator followed by a diagonal transformation . Therefore, we will refer to this normalization as model or image normalization. Since has the inverse units of , the normalized image is unit-less.
Given that each row of corresponds to an output bin, is therefore normalization by the coverage after imaging. We refer to this coverage as the imaging fold, e.g, AMO fold, DMO fold ... etc.