Infrastructure maintenance often involves comparisons between both the surveyed and modelled state of the infrastructure, and also comparisons between the state in successive periods in order to determine what changes have occurred. This is the case, for example, for managing seafloor depths before and after dredging. It is also relevant for vertical structures such as quay walls that can deform over time due to the pressure above ground, or that can be undercut by the movement of water.
A rich variety of tools can work on raster surface representations of lidar and sonar surveys. A first step is to produce these raster surface representations. The tools described in this section provide additional capability to create raster surface representations of vertical areas. See New Vertical Surface and Set Relevance Distances for more information on creating vertical reference model surfaces.