gravity model

Articles

• Spatial interaction
  3 December 2004, by Cl. G.

  Although the notion of spatial interaction plays a central role in the definition of contemporary geography, it is extremely difficult to define, so various are the definitions that have been proposed for it. An attempt may however be made to make a rough classification of these definitions in order to distinguish between what constitutes the heart of the notion, and what points to extensions of it and the theoretical issues it raises.
  1. The spatial interaction and gravity model.A (...)

• Polarisation
  12 January 2005, by B. E.

  The concept of polarisation covers two distinct acceptations in Geography:
  A classical acceptation synonym of concentration of matter and energy. Polarisation is the attraction exerted by a place on a more or less extended and heterogeneous space that is in a situation of dependency with respect to this centre. Space is compared to a magnetic field in which a place, assimilated to a pole (generally a city or a region) exerts a magnetisation proportional to its population, to its activities (...)

• Friction
  6 October 2004, by D. P.

  Friction of distance is an expression that is sometimes used in order to designate the attenuating effect of distance on intensity of interactions between places, or else, in gravity models, the parameter measuring this gradient.

• Gravity model
  6 October 2004, by D. P.

  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 universal gravitation: two objects attract each other in direct proportion of their masses and in inverse proportion of the distance separating (...)

• Theories of spatial analysis
  12 January 2005, by D. P.

  The general theoretical position of spatial analysis consists in proposing a partial explanation as well as prediction possibilities about the state and probable evolution of geographical objects / entities, on basis of knowledge of their situation with respect to other geographical objects.
  There exists not yet any general theory of geographical space that could be a theory of concentrations, of spacing, of spatial structures and of evolution of spatial systems, relying on knowledge of (...)

• Attraction, attractiveness
  13 October 2004, by D. P.

  (from Latin attrahere "to pull towards oneself")
  From observation of flows between places, is deducted by analogy the existence of a force of attraction exerted by attributes of a place (site, resources, mass,...) on actors of another place. Attractiveness is a measure of the force of attraction of a place, generally function of the sum of flows attracted by this place.
  See also : Gravity (...)

• Theories of spatial analysis
  3 December 2004, by D. P.

  The general theoretical position of spatial analysis consists in proposing a partial explanation as well as prediction possibilities about the state and probable evolution of geographical objects / entities, on basis of knowledge of their situation with respect to other geographical objects.
  There exists not yet any general theory of geographical space that could be a theory of concentrations, of spacing, of spatial structures and of evolution of spatial systems, relying on knowledge of (...)

• Interaction
  6 October 2004, by D. P.

  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 changes in behaviours or in structures. The term was introduced into a theory of movement by E.L.Ullman, who set as (...)

• Law
  6 October 2004, by D. P.

  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 residual with regard to a model); the term law is often considered as too strong and replaced by rule, or regularity, as the observed relations do not reflect (...)

• Flow
  6 October 2004, by L. C.

  Is called flow the circulation, the transfer of a given amount of persons, vehicles, information, goods carried by communication means.
  When this quantity is related to a time unit, this gives a rate of flow. The rate of flow is thus a measure of circulation that varies according to the type of flow under study.
  For example, road traffic is measured in Passenger Car Unit (PCU) per hour, transfer of information through the Internet is measured in bauds (per second), water conveyance in (...)

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