The only other restriction is that the surface to be mapped be single-valued. That is, every location in X must have only one associated value Z. If a data location has multiple Z values, then the values can be averaged or duplicate values can be deleted.
In addition to reading in X-Y-Z data, the program can read in pre-gridded matrices. In that case, the file contains only Z values, arranged in rows and columns. The X and Y values can be generated by knowing the row and column spacings and the coordinates of the matrix boundaries.
The user can also enter outline data. Outlines such as county lines, highways, lakes, and so on can be read into the program and overlain on maps.