Recall that each column of corresponds to an impulse response. We therefore apply column scaling to imaging operators implemented as push operators. The system we solve is then
In equation equ-dat the imaging operator is applied after the data have been normalized by and, consequently, we will refer to this normalization as data normalization. Again we notice that has the inverse units of making the output image unit-less.
Similarly to the imaging fold defined earlier, is normalization by the coverage of the modeling operator (where ). We will refer to this coverage as the modeling fold.