Map of axis lines in Braslia. The colors

show the global integration of the different

streets, measuring the accessibility of a

topological line for the entire system

according to the spatial analysis of the

space syntax. Created with Mindwalk 1.0

Space syntaxFrom Wikipedia, the free encyclopedia

The term space syntax encompasses a set of theories and techniques for theanalysis of spatial configurations. I was conceived by Bill Hillier, JulienneHanson and colleagues at The Bartlett, University College London in the late1970s to early 1980s as a tool to help architects simulate the likely social effectsof their designs.

Contents

1 Thesis1.1 Applications

2 History

3 Criticism4 See also5 References6 External links

Thesis

The general idea is that spaces can be broken down into components, analyzedas networks of choices, then represented as maps and graphs that describe the relative connectivity and integration of thosespaces. It rests on three basic conceptions of space:

an isovist (popularised by Michael Benedikt at University of Texas), or viewshed or visibility polygon, the field of viewfrom any particular pointaxial space (idea popularized by Bill Hillier at UCL), a straight sight-line and possible pathconvex space (popularized by John Peponis and his collaborators at Georgia Tech), an occupiable void where, ifimagined as a wireframe diagram, no line between two of its points goes outside its perimeter: all points within thepolygon are visible to all other points within the polygon.

The three most popular of analysing a street network are Integration, Choice and Depth Distance.

Integration measures how many turns have to be made from a street segment to reach all other street segments in thenetwork, using shortest paths. If the number of turns required for reaching all segments in the graph is analyzed, theanalysis is said to measure integration at radius 'n'. The first intersecting segment requires only one turn, the second twoturns and so on. The street segments that require the fewest turns to reach all other streets are called 'most integrated'and are usually represented with hotter colors, such as red or yellow. Integration can also be analyzed in local scaleinstead of the scale of the whole network. In the case of radius 4, for instance, only four turns are counted departing fromeach street segment.

Theoretically, the integration measure shows the cognitive complexity of reaching a street, and is often argued to 'predict' thepedestrian use of a street: the easier it is to reach a street, the more popular it should be. While there is some evidence of thisbeing true, the method is biased towards long, straight streets that intersect with lots of other streets. Such streets, as Oxford

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Street in London, come out as especially strongly integrated. However, a slightly curvy street of the same length would typicallybe segmented into individual straight segments, not counted as a single line, which makes curvy streets appear less integrated inthe analysis.

The Choice measure is easiest to understand as a 'water-flow' in the street network. Imagine that each street segment isgiven an initial load of one unit of water, which then starts pours from the starting street segment to all segments thatsuccessively connect to it. Each time an intersection appears, the remaining value of flow is divided equally amongst thesplitting streets, until all the other street segments in the graph are reached. For instance, at the first intersection with asingle other street, the initial value of one is split into two remaining values of one half, and allocated to the twointersecting street segments. Moving further down, the remaining one half value is again split among the intersectingstreets and so on. When the same procedure has been conducted using each segment as a starting point for the initialvalue of one, a graph of final values appears. The streets with the highest total values of accumulated flow are said tohave the highest choice values.

Like Integration, Choice analysis can be restricted to limited local radii, for instance 400m, 800m, 1600m. Interpreting Choiceanalysis is trickier than Integration. Space syntax argues that these values often predict the car traffic flow of streets, but, strictlyspeaking, Choice analysis can also be thought to represent the number of intersections that need to be crossed to reach a street.However, since flow values are divided (not subtracted) at each intersection, the output shows an exponential distribution. It isconsidered best to take a log of base two of the final values in order to get a more accurate picture.

Depth Distance is the most intuitive of the analysis methods. It explains the linear distance from the center point of eachstreet segment to the center points of all the other segments. If every segment is successively chosen as a starting point, agraph of accumulative final values is achieved. The streets with lowest Depth Distance values are said to be nearest to allthe other streets. Again, the search radius can be limited to any distance.

Applications

From these components it is thought to be possible to quantify and describe how easily navigable any space is, useful for thedesign of museums, airports, hospitals, and other settings where wayfinding is a significant issue. Space syntax has also beenapplied to predict the correlation between spatial layouts and social effects such as crime, traffic flow, and sales per unit area.

History

It has grown to become a tool used around the world in a variety of research and areas and design applications in architecture,urban design, planning, transport and interior design. In general, the analysis uses one of many software programs that allowresearchers to analyse graphs of one (or more) of the primary spatial components.

Over the past decade, space syntax techniques have been used for research in archaeology, information technology, urban andhuman geography, and anthropology. Since 1997, the space syntax community has held biennial conferences, and many journalpapers have been published on the subject, chiefly in Environment and Planning B (http://www.envplan.com).

Criticism

Space syntax's mathematical reliability has recently come under scrutiny because of a number of paradoxes that arise undercertain geometric configurations. These paradoxes have been highlighted by Carlo Ratti at the Massachusetts Institute ofTechnology, but denied in a passionate academic exchange with Bill Hillier and Alan Penn [2004]. There have been moves toreturn to combine space syntax with more traditional transport engineering models, using intersections as nodes and constructingvisibility graphs to link them, by researchers including Bin Jiang, Valerio Cutini and Mike Batty. Recently there has also been

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research development that combines space syntax with geographic accessibility analysis in GIS, such as the place syntax-models developed by the research group Spatial Analysis and Design at the Royal Institute of Technology in Stockholm,Sweden.

See also

Permeability (spatial and transport planning)Spatial networkSpatial network analysis softwareUrban planningVisibility graph analysisFuzzy architectural spatial analysis

References

Hillier B. and Hanson J. (1984), The Social Logic of Space, Cambridge: Cambridge University Press.Hillier B. (1999), Space is the Machine: A Configurational Theory of Architecture, Cambridge: CambridgeUniversity Press.Hillier B. and Penn A. (2004), Rejoinder to Carlo Ratti. Environment and Planning B - Planning and Design, 31 (4),487499.Jiang B. and Claramunt C. (2002), Integration of space syntax into GIS: new perspectives for urban morphology(http://fromto.hig.se/~bjg/transactiongis.pdf), Transactions in GIS, 6 (3), 295-309.Ratti C. (2004), Space syntax: some inconsistencies. Environment and Planning B - Planning and Design 31 (4),501511.

External links

Environment and Planning B special issue (v. 30, no.5) on Visibility Analysis contains several articles on visibility in urban

and natural environments: [1] (http://www.envplan.com/epb/epb30_contents.html#iss5)Article by C. Ratti: http://senseable.mit.edu/papers/pdf/2004_%20Ratti_Environment%20and%20Planning%20B01.pdf

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