Walter Christaller

Christaller introduced the conceptual framework that is Central Place Theory (CPT) in 1933. Central Place Theory essentially states that if an area of land is flat and featureless and there is an even distribution of population, as well as equal money and transport opportunities, then settlements will follow a distribution pattern according to their size. CPT attempts to illustrate the concepts of threshold and range of settlements, how settlements locate in relation to one another as well as dealing with hierarchy of settlements.

Threshold and Range

The minimum sales that an establishment must secure in order to survive is the threshold population. The relationship between threshold population and number of establishments is exponential (similar to y=e^-x).

The range is the maximum distance the population is prepared to travel to purchase goods from a central place. This will be different for convenience and comparison goods, in general people are willing to travel further for comparison goods than they are for convenience. Hence convenience goods will have a short range and comparison a long range.

Hierarchy

This is exactly what I mentioned about in the ‘Rural Characteristics’ blog post when I spoke about the function and hierarchy of a settlement. Hierarchy is essentially made up of three steps: first, the higher order settlements are generally larger in size and offer more functions; second, higher order settlements occur less frequently, and as such, are spaced further apart. Finally the hierarchy is stepped as can been seen in the graph in the ‘Rural Characteristics’ blog post.

Nesting

This is the main part of central place theory that the S-cool website goes into. Each settlement is surrounded by a market area it serves. The largest settlements are found at the centre of the hexagons and are surrounded by smaller settlements. The larger the settlement, the greater the market area. The idea is that people from the small villages will only visit their large settlements for anything not provided by the village - they cannot cross the boundaries.

The distribution of nesting will follow one of three patterns: Firstly, Market Optimising. In this pattern, shoppers in the smaller settlements divide into three equal groups when shopping in the three larger settlements.

Second: Transport Optimising. Shoppers in the smaller settlements divide into two equal groups when shopping in the two nearest large settlements.

Third, and finally: Administration Optimising. All shoppers in the smaller settlements shop in the nearest large settlement. 

References

Nagle and Spencer, 1997. Advanced Geography Revision Handbook. Oxford University Press.

http://www.britannica.com/EBchecked/topic/102569/central-place-theory

http://www.s-cool.co.uk/a-level/geography/urban-profiles/revise-it/central-place-and-bid-rent-theories