Associated surfaces are not required, but can be derived and/or loaded when needed for deriving error surfaces using a fuzzy inference system. Typical inputs include slope, point density, roughness and point quality, but the user can load any surface (assigning the [Undefined] type tag).
By default, associated surfaces take on the name of the type of surface you derive or the name of the file you load. The Original source shows where the raster (if loaded) comes from, whereas the Project raster path shows where the associated surface will be stored within the GCD Project. The type of associated surface is just a tag to make it helpful for identifying the correct input when deriving FIS error surfaces. There are five built-in types and one undefined type:
The various ways to load an associated surface are shown in the sub commands: