ABSTRACT
In the previous chapter, a conceptual framework for GIS was presented, in which four transformation stages were identified. GIS provide a mechanism by which geographic data from multiple sources may be built into a digital model of the geographic world. This model may be manipulated and analysed to extract many types of geographic information. The first two of these transformations are data collection (T1) and input (T2), shown in Figure 4.4. Many GIS commentators have tended to ignore or under-estimate the influence of data collection on subsequent operations, and begin with discussion of data input methods. We have seen how the transformations which data undergo may fundamentally affect their usefulness at later stages, and for this reason, collection and input are considered together in this chapter. Recent interest in the sources of error in spatial data have focused attention more clearly on the methods used for collection and input.
