Vertical planes can be modelled in a reference model by choosing two x,y locations and two depths for each point. That produces a rectangular vertical wall in general. However, the walls can be customized by assigning one of the two x,y locations to have a single depth, resulting in a triangular vertical wall. If digitizing a vertical surface along two existing complete reference model surfaces, the depths and orientation for the vertical surface are automatically determined from the existing surfaces. This simplifies the modelling of infrastructure such as quay walls. Vertical surfaces can be created, added to and removed from supersurfaces and templates. They can also be viewed in 3D.