Several general purpose contouring programs are available. Their effective use requires a knowledge of ways in which the programs operate and the types of applications most suited to machine-contouring techniques.

Machine contouring is not applicable to most one-pass jobs involving the use of considerable scientific judgment or combinations of different types of data; e.g., gradient and point values derived from data that have not been put in machine-readable form. By contrast, machine contouring is a valuable technique in analyzing large masses of data or in routine updating, in analysis of data that do not require a scientific bias for interpretation, in making a suite of maps that is to be made internally consistent; and in further analysis of resulting surfaces.

Most general purpose contour programs follow similar steps in the generation of a map. These steps include (1) specification of map size and accuracy desired, (2) entering raw data to be contoured, (3) generation of a grid from irregularly spaced points, (4) creation of contour lines, and (5) special annotation and other additional features in certain programs. Grid generation is the most important component of the program and there are several techniques for generating grids.

Familiarity with these principles will enable the user to interact more effectively with the program at his disposal, and to create, store, combine, and analyze the surfaces generated in a way which will enhance his scientific investigation.