ABSTRACT

The common feature of global GIS operations is that their result at some location may depend on input values at locations in the study area that are remote from the location of interest. In other words, global operations include far-reaching spatial interactions. Typical examples of global operations are Spread, Viewshed, Stream and Pathway (Burrough, 1986; Tomlin, 1990; Burrough and McDonnell, 1998). This type of operation is routinely applied to digital elevation models and cost surfaces, such as used to determine the optimal trajectory of a highway in a landscape (Tomlin, 1983), or for automated drainage network analysis (Kovar and Nachtnebel, 1993; Van Deursen, 1995).