Christaller attempted to explain the size, number, and distribution of clusters of urban centers and institutions. He built upon the works of von Thünen and Weber. Christaller believed that, in order to adequately explain the spacing of urban places over the landscape, it was necessary to create a set of governing assumptions. To do this, he developed three two-dimensional geometric models of the economic landscape. He arranged these models relative to marketing, transport, and administrative principles.
Christaller developed his model using the following assumptions:
- The existence of a flat, limitless plain. This removes real-world physical differences that might change the location of transportation routes, communities, businesses, and so on.
- A rural population that is spread evenly over the landscape.
- A homogenous transportation surface so that a person can move in any direction with equal ease.
- The first three assumptions involve an initial stage of development of an economic landscape. The evolution of this landscape is based completely on the development of tertiary activities.
In Christaller's model, each settlement is situated in the center of the region it serves. Logically (assuming no restrictions), this should result in a circular complementary (market or service) region. If we assume that the threshold for customers who shop in hardware stores is fifty miles, then it would follow (in keeping with Christaller’s assumptions) that on a flat plane, we should be able to find hardware stores in centers located fifty miles apart. Such an arrangement on the landscape, however, would leave areas that are not served by any hardware facilities. Thus, the most efficient shape for a service area (in the Christaller model) is not a circle, but a hexagon.
In the example above, notice overlapping areas. This would create overlaps in the service areas, and would therefore jeopardize the evaluative utility of Christaller's model.
If Christaller had built his model around circular service areas, it would have resulted in a situation in which the service areas overlapped, or if they did not overlap, some people could not gain access to service. The first case would result in two or three centers competing for the same market area, and thereby would bring about a distortion of the model that could result in a failure to reach a minimum customer threshold for many of the centers. In such a situation, the model would not be useful as a tool of spatial investigation. Thus, Christaller decided to use a hexagonal pattern, and to set threshold limits within the perimeters of these hexagons. Under such idealized conditions, the arrangement of central places is geometrically predictable, and all complementary regions are of the same size and shape. Additionally, the hexagons interlock into one another, and form a nested hierarchy as well. Thus, each central place is equidistant from six surrounding centers.
In this simplistic situation, the central-place theory model is deterministic. It is deterministic, because if one knows the location and the range of two central places, he or she also knows the location of all other places on the plane.
Check Your Understanding
Characterize the essence of Walter Christaller's urban land-use theory.
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Christaller's model is based on a number of basic spatial concepts. According to Christaller, trade patterns and urban patterns can be predicted (for a region that is a flat plane without any other mitigating variables) based upon the threshold and range of various goods and services offered. For example, a small hamlet will offer only those items with a relatively short range (e.g., things like bread, or gasoline because people will not travel far to acquire these things), whereas a high-order place (large trade center) will offer a full assortment of goods and services. As a result of this, Christaller came to the conclusion that market centers naturally organize in a hexagonal pattern in which six lower order places surround each higher order place.