The processing order is not restricted, but, in general, the output of a step is the input for the next. The following flowchart (Figure 1.2) shows the general processing order. The black processing steps are obligatory to obtain a geocoded interferogram as end product. The dark gray steps are highly recommended, whereas the light gray steps are optional. Obviously, the modular structure of Doris enables the user to specify its own processing chain. The most important (intermediate) products are indicated on the right-hand side.