the gauteng spatial development framework - Gauteng Online

THE CONNECTIVITY MODELANNEXURE A: THE 5 GIS-BASED MODELSThe Connectivity Model models the degree of spatial integration (or lack thereof) of theGCR as a whole such that one can discern those parts or elements of the GCR that are wellintegrated (and therefore, presumably, showing relatively high levels of urban achievement)and those parts that are relatively disconnected (and therefore, in many instances, likely tobe showing high levels of marginalisation from the urban system). At one level, theconnectivity model is a tool for searching the urban system for diagnostic clues to theeffectiveness or otherwise of the urban structure.More importantly, however, it is a tool for examining the likely effects of additionalinfrastructure aimed at increasing the urban integration of an area. For example, an areasuch as Soweto, despite its very large population, is poorly connected to the wider urbansystem for historical reasons and much of Soweto's future achievement as an importantsector of the GCR (and Johannesburg more particularly) relies substantially on improvingits spatial integration with the wider system. The connectivity model assists in therefore(a) in detecting the lack of connection and (b) testing what infrastructural improvementsin this regard would be most effective.The principle behind the Connectivity Model is that spatial elements (linear movementelements in this case) can be broken down into components, analysed as networks ofchoices, and represented as maps and graphs that describe the relative connectivity andintegration of those spaces.Whilst there are a number of analysis methods of a street network, such as Integration,Choice and Depth Distance, our main concern with the current exercise is the measure ofIntegration and Depth:Integration measures how many turns one has to make from a street segment to reachall other street segments in the network, using shortest paths. The first intersecting segmentrequires only one turn, the second two turns and so on. The street segments that requirethe least number of turns to reach all other streets are called 'most integrate' and are usuallyrepresented with hotter colours, such as red or yellow.Depth, in the context of the Connectivity Model, is a process that measures the lineardistance from the centre point of each street segment to the centre points of all the othersegments. If every segment is successively chosen as a starting point, then a graph ofaccumulative final values is achieved. The streets with lowest Depth Distance values are saidto be nearest to all the other streets.The results of this Connectivity Model provide a spatial representation that shows areas thatare well integrated, and thus more accessible, and areas that are more segregated, withlower levels of accessibility. In the current exercise, the Connectivity Model has been processedwith a number of different structural iterations.The Connectivity and Bid-Rent Models are both concerned with understanding a commonissue: The Social Logic of Space, i.e. how to understand the interrelationships betweendifferent spaces, the factors that define these interrelationships, and the way in which tooperate within these interrelationships.The connectivity model provides a means of exploring the 'metric' properties of a spatialstructure, whilst the bid-value model explores a wider range of 'topological' relationships.107 GAUTENG SPATIAL DEVELOPMENT FRAMEWORK 2011 GAUTENG GROWTH AND DEVELOPMENT AGENCY