1A_4_GIS enhances collaboration: using the line to draw disciplines together

Editor's Notes

• #4: For many years, the rhetoric surrounding planning decisions in town centres has been driven primarily by retail activity. It is a commonly held belief that retail activity is the primary generator of the vitality and viability of high streets. In reality the composition of activities of town centres and their hinterlands are much more intricately interwoven. Indeed, initial analysis, conducted as part of the Towards Successful Suburban Town centres project, found that suburban town centres are complex, distinct centres comprised of multi-scaled interactions between land use activities, population and its built environment. This complexity of interactions contributes to the vitality of such centres as places for living, working, shopping and leisure (Vaughan et al, 2009).
• #5: To explore the detailed multi-scaled interactions of these centres, it is necessary to draw upon a range of methods to enable the geographical analysis of social and economic activities at various scales of accessibility and integration within the built environment. Of particular importance is the notion that network properties of the street plan exert an influence on pedestrian and vehicular movement patterns which have a bearing on the distribution of land use activities beyond just that of retail activity. An exploration of these relationships informs policy and planning decision making as well as urban design. The type of geographic enquiry required to further our understanding lends itself to the examination of the complex relationships between land use activity and the structure of the built environment – bringing together interdisciplinary methods found in geography and architecture. The visualisation and quantification of (sub) urban form using space syntax methodology is of particular interest. It enables the spatial structure, accessibility and connectivity of streets and the layout of the buildings to be adjoined and then compared with information about the land use activities taking place within the suburban centres and its hinterland. To understand how the entities interact together, first they must be understood and only then can we model the relationships of how they interact. The paper describes how space syntax methods developed in the field of architectural research to produce quantitative descriptions of built form and street networks can be enriched by using GIS as the mechanism for bridging between disciplines. It illustrates how the resulting structural knowledge of the built environment can complement socio-economic analysis by providing a robust geographic base for measurement and analysis. This paper describes a methodology for disciplinary integration; first through the development of a point-line algorithm used to define and model the disjoint geographical relationship of entities in suburban town centres; and then how the resulting GIS data serves space syntax analysis itself and also acts as a collaborative tool for interdisciplinary investigation. It outlines the development of a cohesive geographical framework to aid the linkages between disciplinary practices and stresses the usefulness of the line as a predictor of movement potentials and as a suitable analytical measure for exploring land use activities.
• #6: Research into the built environment has suffered due to a lack of collaboration and the incompatible nature of analytical toolsets by built environment specialists and human geographers (Jones et al., 2009). Space syntax theory and methodology is a powerful means of exploring the spatial configuration of the built environment. It uses quantitative analysis derived from graph theory and is represented by network maps (Hillier and Hanson 1984; Hillier and Iida 2005). However, for human geographers this emphasis on physical structure seemingly marginalises socio-economic processes (Soja 2001), as it seems to imply a environmental determinism associated with the discredited positivism of geography’s ‘quantitative revolution’ of the post-war period (Johnston and Sidaway 2004). The geographers’ critique is represented in figure 1(a) in which an over-determined built environment renders human activity as anonymous and mechanistic. By contrast, research in the field of space syntax argues that human geography prioritises the social construction of space at the cost of considering how this interacts with the built environment of the lived space (Hillier 2008). The world view of the human geographer, from the space syntax perspective, is illustrated in figure 1 (b) where human activity is represented against an undifferentiated background. Clearly there is a need to be sensitive to both perspectives if we are to understand the relation of the structure of the built environment to human activity, illustrated in figure 1 (c).
• #7: Urban designers – looking from a different developed a methodology known as Space Syntax. It is quantitative analysis derived from graph theory and is represented by network maps (Hillier and Hanson 1984; Hillier and Iida 2005) These are drawn by first exploring the structure of the built environment as derived by the buildings and the streets on shown in the slide. Once the physical environment has been defined a network graph is created. This network graph represents the connectivity of the open space as defined by the street network. The graph connects lines of sight as approximated by the longest Straightest paths through the street network.
• #8: The graphs visualise the connectivity of open space in the physical environment and as such can then be used to understand the different types of movement potential of people and cars through it based on different measures of connectivity. The graph can then be analysed at various scales which are used to understand movement for local, regional and national scales. They are coloured using a continuous colour spectrum where red = lots of movement potential and blue = not a lot of movement potential. This image shows the potential movement at a scale of 2 km for the town centre of Surbition. We can see the importance of the high street.
• #9: The problem faced by the Towards Successful Suburban Town Centres Project was associated to the different world views that existed between urban designers and geographers. Space Syntax is a relatively young research field having only been developed in the 1970s and so there has been little formal collaboration between differnt disciplines beyond using GIS to create thematic maps. We faced the challenge of Incompatible tool sets developed in isolation together with an inconsistent analytical framework. In order to unite the disciples, it is first necessary to identify two issues: (1) a lack of automated procedures that allow different graphical entities to be linked together [1] and (2) the absence of coherent shared methodologies and practices between the disciplines.
• #10: In order to develop a coherent perspective across disciplines we first need to model the relationship between the space syntax network and the different types of urban land uses. A coherent analytic framework based on the network was developed
• #11: So we first had to build a collaborative analytical framework with a geographical base to connect to the disparate entities; the syntax graph and the land use points ( There is no common attribute between the two entities). This is because they have dissimilar spatial forms, corresponding to the very distinct geographic components they characterise. The land uses are stored as points (figure 2b) and the space syntax graph as an abstract network of lines represents the shape and structure of the suburban built environment (figure 2c). We set out to develop a robust and consistent tool for modelling the relationship between the structure of built environment and functional land use distribution in suburban town centres.
• #12: An algorithm based on coordinate geometry was written; its purpose, to define the correct spatial relationship between the lines and the points. 3 different disparate datasets with different attributes based on a point-line search algorithm that linked space syntax graphs to the roads and then using the road names to then link the land use to the space syntax graph. Land use data was stored as points derived from the Ordnance Survey Address Layer 2 product, has a full UK address attribute.
• #13: The results of the algorithm was a new geographic base framework with a very large data matrix attached. The results were used to scrutinise the geographic relationships between the land-use and the associated movement potential of the street it is located on - so that we could better understand the relationships between movement potential and land use activity within London’s suburban town centres. We decided to explore the Local Spatial Autocorrelation between the movement and the landuse to investigate any geographical clustering for the two variables.
• #14: A number of initial finding have occurred. The first reaffirmed the geographical clustering of retail activity along highly accessible movement paths of high streets in town centres. Of particular interest to the project is the pattern of non-residential land-use that are associated with movement generation and activities. The clustering of retail activity suggests the geographical dependence of other types of non residential activity located off the high street and on locally integrated streets that are not routes where you would expect lots of through movement, indicating suburban high streets function not only as retail centres but that there is a more complex pattern of activity that ensures their vitality.
• #15: In order to explore this idea we looked at the distribution of segments according to residential and non-residential activity and also adopted ideas for ecology based on the notion that thriving eco-systems required richness of species – we also looked at the number of different types of activities that occured on each segment – to gain an understanding of activity richness. The initial results reveal a clear longtail we there are fewer non-residential segments with fewer segments with have a larger number of different activities
• #16: To get more understanding on the general pattern of non-residential activity a bi-variate LISA analysis was performed between the land uses classed as non-residential and the to paths of movement potential in Town Centres The results demonstrate that routes through a town centre integrated at a scale of 1km are clustered significantly with all non-residential land uses activity. This reveals the importance of active segments beyond that of the retail High Street. This suggests that there is geographical dependence of other types of non residential activity located off the high street and on locally integrated streets that are not routes where you would expect lots of through movement, This maybe evidence that suburban centres not only function not only as retail centres but that there is a more complex pattern of activity that ensures their vitality.
• #17: The results of the algorithm led to the development of a coherent data structure based upon the network of movement potential in each town centre. The line entity became the object of priority and is symbolic of the linkages between disciplines. Thus, it is the semantic meaning of these two geographical objects that is of relevance to this paper. This fusion of the disciplines, the results of the geometric algorithm, represents the creation of a new phenomenon. The developed algorithm facilitated the amalgamation of two quite different world views with incongruent analytic frameworks. In one discipline the line object provided the mechanism for understanding the morphological properties of the town centres and in the other the point afforded investigation of the socio-economic properties of a centre’s land use activities. Up until this point the two disciplines had not been as fully synthesised.   Furthermore linking the two disciplines produced findings with new insights that otherwise would not have been revealed. This synthesis between the disciplines also led to the development of a useful and usable analytical framework centred upon the line object. Thus, proving GIS as feasible mechanism for collaboration between Space Syntax and Human geography. GIS assisted in the development of automated procedures to allow the linking of different entities and the formulation of coherent shared methodologies and practices between the disciplines. The methodology developed in this paper contributes to the debate on the usefulness of GIS as a basis for driving collaborative research, illustrating how a geographical framework can be used to develop a methodology that is mutually beneficial for human geographers and space syntax specialists alike.