In physics, equilibrium is the state of a system subjected to opposite forces that balance each other, so that the variables describing the system stop evolving and any move is stopped. In geography, what may rather be observed are stationary states, when equality of incoming and outgoing flows of an open system implies that there […]
(term proposed by B. Mandelbrot) In mathematics, a fractal is a geometrical object such that the same properties are showing at different scales. There is thus a hierarchically organised structure, which follows a well-defined hyperbolic law, either determinist (regular fractal) or stochastic (random fractal): n(e) = e -D where e is the measure interval(variable parameter […]
Is called gradient the variation of intensity of a phenomenon per unit of distance between a place and a given centre (or axis). It is the case for example with density gradients which develop around a city centre, gradients of population, facilities, shops, services, gradients of land prices, etc. gradients of population which appear on […]
In statistics, a distribution is random or stochastic or realised by chance, when its composing elements may occur at any moment in time or may appear in any location with some probability. A random distribution may however follow a characteristic process that gives it a particular form (e.g. Poisson distribution, normal distribution, law of Galton-Gibrat). […]
The notion of hierarchy is used with two distinct meanings. It is a social, political or administrative organisation in levels where each element belonging to a level is strictly subordinated to an element of upper level. The higher it is gone in the order of power or domination, the fewer elements are comprised in each […]
The notion of homogeneity describes the greater or lesser equality of values of a variable or of a combination of features in a geographical set. Parameters of statistical dispersion, such as variance, measure its converse, heterogeneity. The homogeneous region is a type of region defined by a greater similarity among the units that compose it […]
An interaction is a reciprocal action (retroaction) between two or more actors or places in a system. All exchanges (of matter, persons, information…), for example at individual level between producer and customer, between partners, or at aggregate level between cities or regions (these are the spatial interactions), are interactions as far as they generate interdependent […]
A law is a general formula expressing a constant or usual relation between phenomena; laws brought to the fore by science of nature apply in physical geography; in human geography, laws are the necessary reference for the explanation, whether the object under study conforms itself to it or deviates from it (notions of exception, of […]
The gravity model is aimed at formalising, studying and predicting geography of flows or interactions. The distribution of interactions in a set of places depends on their configuration, i.e. the force of attraction of each one and the difficulty of communication between them. The model has first been formulated in analogy with Newton’s law of […]
Set of proposals logically deduced from a few non-demonstrable principles, and which, according to some, may form a basis for geographical analysis. Several types of axiomatics have been proposed : – a geometric axiomatics defining geographical space as a set of places identified by coordinates, separated by a distance and endowed with attributes (Béguin, Thisse, […]