ABSTRACT
The first step in using geographical information systems (GIS), in any application, is to obtain spatial data that are suitable for the user’s purpose (see Chapter 1). Until recently, however, data acquisition was not easy using GIS for the following reasons: (1) the necessary spatial data were often unavailable; (2) spatial data were usually expensive to obtain; and (3) the construction of a spatial database took quite a long time. Fortunately, these problems are now being solved by the development of socio-economic spatial databases and by the progress in spatial data acquisition tools (Longley et al. 1999). Socio-economic spatial data are now provided by both public organizations and private companies and are widely available to GIS users at low cost. Remotely sensed data, which will be discussed in the next chapter, provides us with high-resolution images of the Earth’s surface every day. Global positioning systems (GPS) and mobile GIS enable us to trace the movement of spatial objects. The cost of data acquisition is far less expensive today, and is no longer an impediment to many GIS applications.
