E. Contours: Creation
A contour map is a visual surface model of the terrain. Contours are an end product in traditional paper-based metric mapping. In digital mapping, contours are one way to display the three dimensional model. Whether manual or digital, the general process to create contours is similar.
A major difference between the two environments is understanding what contours are. Manual compilation puts them in control of the mapmaker who knows what contours represent and consequently what they can and cannot do. To software, contours are complex curves consisting of mathematical graphic elements. Left to itself, software can generate contours which violate their basic characteristics. Software is only a tool for faster data manipulation and requires a knowledgeable user to ensure a correct final product. This chapter describes the contouring process in manual terms providing a new user the knowledge to create a correct contour representation in either environment.
Surface model representation resolution depends on its purpose and the accuracy of data used. A later chapter will cover data acquisition methods including collection decisions based on accuracy needs.