Building the theory
To develop the theory, Christaller made the following simplifying assumptions: All areas have: * an unbounded isotropic (all flat), homogeneous, limitless surface ( abstract space) * an evenly distributed population * all settlements are equidistant and exist in a triangular lattice pattern * evenly distributed resources * distance decay mechanism * perfect competition and all sellers are economic people maximizing their profits * consumers are of the same income level and same shopping behaviour * allPredictions
He deduced that settlements would tend to form in a triangular/hexagonal lattice, as it is the most efficient pattern to serve areas without any overlap. In the orderly arrangement of an urban hierarchy, seven different principal orders of settlement have been identified by Christaller, providing different groups of goods and services. Settlement are regularly spaced - equidistant spacing between same order centers, with larger centers farther apart than smaller centers. Settlements have hexagonal market areas, and are most efficient in number and functions. The different layouts predicted by Christaller have ''K''-values which show how much the sphere of influence of the central places takes in — the central place itself counts as 1 and each portion of a satellite counts as its portion:''K'' = 3 marketing principle
According to the marketing principle ''K'' = 3, the market area of a higher-order place (node) occupies one-third of the market area of each of the consecutive lower size place (node) that lies on its neighbour; the lower size nodes (6 in numbers and second larger circles) are located at the corner of a largest hexagon around low value the high-order settlement. Each high-order settlement gets one-third of each satellite settlement (which are 6 in total), thus ''K'' = 1 + 6 × = 3. However, in this ''K'' = 3 marketing network the distance traveled is minimized.''K'' = 4 transport/traffic principle
According to ''K'' = 4 transport principle, the market area of a higher-order place includes a half of the market area of each of the six neighbouring lower-order places, as they are located on the edges of hexagons around the high-order settlements. This generates a hierarchy of central places which results in the most efficient transport network. There are maximum central places possible located on the main transport routes connecting the higher order center. The transportation principle involves the minimization of the length of roads connecting central places at all hierarchy levels. In this system of nesting, the lower order centres are all located along the roads linking the higher order centres. This alignment of places along a road leads to minimization of road length. However, for each higher order centre, there are now four centres of immediate lower order, as opposed to three centres under the marketing principle.''K'' = 7 administrative principle
According to ''K'' = 7 administrative principle (or political-social principle), settlements are nested according to sevens. The market areas of the smaller settlements are completely enclosed within the market area of the larger settlement. Since tributary areas cannot be split administratively, they must be allocated exclusively to a single higher-order place. Efficient administration is the control principle in this hierarchy.Evaluation
The validity of the place theory may vary with local factors, such as climate, topography, history of development, technological improvement and personal preference of consumers and suppliers. However, it is still possible to discern Christaller patterns in most distributions of urban centres, even though these patterns will often be distorted by the terrain or imperfect because of suboptimal (with regard to the optimal distribution of centres) historical development decisions. Economic status of consumers in an area is also important. Consumers of higher economic status tend to be more mobile and therefore bypass centers providing only lower order goods. The application of central place theory must be tempered by an awareness of such factors when planning shopping center space location. Purchasing power and density affect the spacing of centers and hierarchical arrangements. Sufficient densities will allow, for example, a grocery store, a lower order function, to survive in an isolated location. Factors shaping the extent of market areas: *Examples
The newly reclaimedCriticism
The central place theory has been criticized for being static; it does not incorporate the temporal aspect in the development of central places. Furthermore, the theory holds up well when it comes to agricultural areas, but not industrial or postindustrial areas due to their diversified nature of various services or their varied distribution of natural resources.Newer developments: a dynamic concept for CPT
Newer theoretical developments have shown that it is possible to overcome the static aspect of CPT. Veneris (1984) developed a theoretical model which starts with (a) a system of evenly distributed ("medieval") towns; (b) new economic activities are located in some towns thus causing differentiation and evolution into a hierarchical ("industrial") city system; (c) further differentiation leads into a post-hierarchical ("postindustrial") city system. This evolution can be modelled by means of the three major CPT theories: stage (a) is a system of von Thünen "isolated states"; stage (b) is a Christallerian hierarchical system; stage (c) is a Löschian post-hierarchical system. Furthermore, stage (b) corresponds to Christopher Alexander's "tree" city, while (c) is similar to his "lattice" system (following his dictum "the city is not a tree").The importance of a city and other theoretical considerations
According to Margot Smith, Walter Christaller erred in his development of CPT in 1930 by using size of population and number of telephones in determining the importance of a city. Smith recognized that although population size was important to the area served by a city, the number of kinds of services offered there was more important as a measure of the importance of a city in attracting consumers. In applying CPT to describe the delivery of medical care in California, Smith counted the number of physician specialties to determine the importance of a city in the delivery of medical care. Christaller also erred in the assumption that cities "emerge". In California and much of the United States, many cities were situated by the railroads at the time the tracks were laid. In California, towns founded by the railroads were 12 miles apart, the amount of track a section crew could maintain in the 1850s; larger towns were 60 miles apart, the distance a steam engine could travel before needing water. Older towns were founded a day's horse ride apart by the Spanish priests who founded early missions. In medical care regions described by Smith, there is a hierarchy of services, with primary care ideally distributed throughout an area, middle sized cities offering secondary care, and metropolitan areas with tertiary care. Income, size of population, population demographics, distance to the next service center, all had an influence on the number and kind of specialists located in a population center. (Smith, 1977, 1979) For example, orthopedic surgeons are found in ski areas, obstetricians in the suburbs, and boutique specialties such as hypnosis, plastic surgery, psychiatry are more likely to be found in high income areas. It was possible to estimate the size of population (threshold) needed to support a specialty, and also to link specialties that needed to cooperate and locate near each other, such as hematology, oncology, and pathology, or cardiology, thoracic surgery and pulmonology. Her work is important for the study of physician location—where physicians choose to practice and where their practices will have a sufficient population size to support them. The income level of the population determines whether sufficient physicians will practice in an area and whether public subsidy is needed to maintain the health of the population. The distribution of medical care in California followed patterns having to do with the settlement of cities. Cities and their hinterlands having characteristics of the ''traffic principle'' (see K=4 above) usually have six thoroughfares through them—the thoroughfares including highways, rivers, railroads, and canals. They are most efficient and can deliver the lowest cost services because transportation is cheaper. Those having settled on the market principle (K=3 above) have more expensive services and goods, as they were founded at times when transportation was more primitive. In Appalachia, for example, the market principle still prevails and rural medical care is much more expensive.Making central place theory operational
CPT is often criticized as being "unrealistic". However, several studies show that it can describe existing urban systems. An important issue is that Christaller's original formulation is incorrect in several ways (Smith). These errors become apparent if we try to make CPT "operational", that is if we try to derive numerical data out of the theoretical schemata. These problems have been identified for by Veneris (1984) and subsequently by Openshaw and Veneris (2003), who provided also theoretically sound and consistent solutions, based on a K=3, 37-centre CP system: #Closure problem. Christaller's original scheme implies an infinite landscape. Although each market has finite size, the total system has no boundaries to it. Neither Christaller, nor the early related literature provide any guidance as to how the system can be "contained". Openshaw and Veneris (2003) identified three different types of closure, namely (a) isolated state, (b) territorial closure and (c) functional closure. Each closure type implies different population patterns. #Generating trips. Following the basic Christallerian logic and the closure types identified, Openshaw and Veneris (2003) calculate trip patterns between the 27 centres. #Calculating inter- and intra-zonal costs/distances. Christaller assumed freedom of movement in all directions, which would imply "airline" distances between centres. At the same time, he provided specific road networks for the CP system, which do not allow for airline distances. This is a major flaw which neither Christaller, nor early related literature have identified. Openshaw and Veneris (2003) calculate costs/distances which are consistent with the Christallerian principles.Central place theory and spatial interaction models
It was once thought that central place theory is not compatible with spatial interaction models (SIM). It is paradoxical however that some times towns or shopping centres are planned with CPT, and subsequently evaluated with SIM. Openshaw and Veneris (2003) succeeded in linking these two major regional theories in a clear and theoretically consistent way: using the data they derived from the operationalization of CPT, they experimented with several SIM. Following a thorough investigation via computer simulation, they reached important theoretical and practical conclusions. Smith was able to delineate medical care regions (the range), describe the hierarchy of medical services, the population base required of each medical specialty (threshold), the efficiency of regions, and the importance of how an area was settled to the delivery of medical care, that is, according to traffic, market or administrative principles.See also
*Notes
References
* Openshaw S, Veneris Y, 2003, "Numerical experiments with central place theory and spatial interaction modelling" Environment and Planning A 35(8) 1389–1403External links