Image Processing Reference
Fig. 6.4 A generalized model of expanding urban spatial patterns
density residential areas. Just as there is typically an inverse relationship between
impervious surface and vegetation outward from the core, there tends to be an inverse
relationship between housing density and income levels, sizes, and costs of homes.
At the urban fringe, scattered patterns of built-up urban features reach into adjacent
farmlands or natural landscapes of forest, grassland, wetland, or barren land. Clearly
there are numerous exceptions to this generalization, but one of the virtues of the
V-I-S model is that whatever the pattern, or changing character of the pattern, the
model is well equipped to identify and document the variation or change.
Time and Change
Urban environments are by their nature dynamic places. Clearly, if they are to be
chronicled over time, a mechanism by which the change in environmental character
can be documented is required. The V-I-S model is well
suited to the task. Cities that are growing generally exhibit
both internal changes and outward expansion. Internally,
impervious surfaces intensify and enlarge around commer-
cial centers, usually replacing vegetation and perhaps some
soil as commercial areas invade the adjacent high density
residential area in transition. Each concentric ring outward
is generally expanding in turn. At the outer fringes of the urban area, the expanding
city commonly invades farmland or, in the case of natural environments, the invasion
replaces forests in humid areas, grassland in semiarid regions, or desert soils in arid
areas, or perhaps wetland. The environmental impact of such invasion is easily and
accurately documented by the V-I-S model.
Long term historical change may require reaching back through earlier, low
resolution imagery or photography. However, the model still applies. Monitoring
contemporary change is likewise implemented with the model. Also, building a
time-line as a base for predicting changing patterns is well-served by the model.