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6708401-The-Shape-of-Habitable-Space.pdf

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62.1 Proceedings . 4th International Space Syntax Symposium London 2003 62 Keywords space,time, experience a.penn@ucl.ac.uk The shape of habitable space Alan Penn University College London, UK Abstract How is it that a representation of the state of a system – such as the axial map – can explain dynamic behaviour such as movement flows? This paper investigates the relationship between spatial configuration and behaviours that take place in time – specifically, movement. A method is presented fo
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  62.1 Proceedings . 4th International Space Syntax Symposium London 2003 62 Keywords space,time,experiencea.penn@ucl.ac.uk The shape of habitable space Alan Penn University College London, UK  Abstract How is it that a representation of the state of a system – such as the axial map – canexplain dynamic behaviour such as movement flows? This paper investigates therelationship between spatial configuration and behaviours that take place in time – specifically, movement. A method is presented for incorporating time systematicallyin a representation of spatial configuration. This is based on assuming a universalmaximum walking speed for pedestrians, and it is shown that the resulting threedimensional mapping of space-time can be constructed from sections of the surfaceof cones. Properties of this representation are investigated and first it is shown thata uniform grid results in an approximately flat surface in space-time. All the mainforms of deformation of the urban grid are found to result in ‘warping’ the space-time surface of the uniform grid into valleys and ridges. A method is proposed for summing space-time surfaces constructed from all root locations. Finally, theimplications for space syntax theory and methodology of the space-timerepresentation are discussed. It is concluded that one of the properties of theconventional axial map is that it internalises aspects of the temporal domain withinits construction, and this may account for its explanatory success. Introduction Space syntax analysis has developed a number of methods for representing andquantifying the morphology of built space. The methods start with the shape of the boundary of space and work back to a subdivision of continuous space into a discretesubset of related ‘spaces’ (such as axial lines or convex spaces) which then form thesubject of study. In working back from the boundary the methods adopt a predominantly allocentric as opposed to an egocentric world view, and thischaracterises the whole theory of the social logic of space. Thus for instance themethods measure how a specific ‘space’ is constituted by its relations to all other ‘spaces’ in a system, while the theory considers an individual’s identity to beconstituted, not only by their own subjective view, but also by the views of all othersin the social group. This approach has been borne out empirically through its abilityto explain various aspects of the social functioning of buildings and urbanenvironments, and through its ability to predict aspects of aggregate human behaviour   The shape of habitable space 62.2 such as average movement patterns over time. There is however considerable interestin understanding the mechanisms at the individual level that give rise to these observedregularities in aggregate behaviour. Here I propose that two factors need to be broughtinto the theoretical and methodological framework if we are to do this. First, theegocentric world view, which considers the morphology of space from an individual’scurrent viewpoint. This brings with it the dimension of orientation or heading, sinceindividuals have a forward facing field of vision. Second, the dimension of timewithin which individuals experience the spatial and social environment. The timedimension brings with it the issue of metric space since individuals can only movewithin a relatively constrained range of speeds. Habitable space In order to investigate this I define ‘habitable space’ as a mathematical space withthe following properties: two spatial dimensions in plan (everything defined herecould be extended to three spatial dimensions, but note that humans are generallyconstrained to move on the ground plane); a time dimension (which I have chosen todisplay vertically); an angle of vision (assumed to be a constant for an individual)and a heading (Figure1).Time represented vertically gives rise to a cone of accessible space-time,thus an individual moving at their maximum speed appears as a path on the surfaceof the cone, if static they trace a vertical path through time with no change in thespatial components. If at a speed less than the maximum the path lies within thevolume of the cone. Their heading, angle of vision and the morphology of theenvironment give rise to a field of view (Figure 2). This field of view defines at anyinstant the range of locations towards which an individual is able to move directly,including points in open space and on the boundary (for example paintings on a wallor doorways to other spatial systems). The visual field at any point also defines theother individuals with whom they are visually co-present in the environment at thattime, and so with whom they can potentially interact ‘face to face’. Headin Angle of vision Figure1: Orientation and angle of vision within a two spatial dimen-sion environment define an indi-vidual’s instantaneous field of view. Their maximum speed de-fines the locations they couldreach within a given time.  62.3 Proceedings . 4th International Space Syntax Symposium London 2003 It should be noted that people are also thinking beings, with imaginationsand memories. They have therefore a more or less well informed understanding of the spatial potential of the system outside the boundary of their current visual field.Thus their decisions on where to move next should generally not be assumed to becompletely (or even mainly) dependent on what they can currently see, but mustoften be informed by their beliefs about the morphology of space beyond their currentvisual field. However, in formulating a plan to reach an objective outside theimmediate visual field, an individual is constrained to move directly towards some point that is currently visible.As an individual moves through space their position changes relative to the boundary of the environment and so does their field of view (Figure 3). In a similar fashion, as they change their gaze direction or heading so their field of view changes.At a particular instant however, the affordances of the environment including theother individuals with whom they can potentially interact are defined by the field of view. This defines the information available to the individual through vision.Movement and change of direction give rise to a landscape in this three dimensionalspace-time. This can perhaps best be represented as a surface made up of sections of the surface of cones. In order to illustrate this for the hypothetical building planshown in Figure 4 these surfaces are developed from two different points of view.Figure 5 shows the surface from a relatively accessible point (A) in the centreof the plan and Figure 6 from a relatively isolated point (B). In each figure the threedimensional surface is shown from four different viewpoints. TimeField of view Time Figure 2: Time cone and field of viewFigure 3: Field of view changesthrough time with movement  The shape of habitable space 62.4 Space-time cone representations share a characteristic of the justified graphused in conventional space syntax analysis: they show differences in spatial relationsfor different root locations, and so show how a root location is ‘constituted’ by itsrelations to other locations in the configuration. In contrast to the justified graphhowever, space-time cones directly represent the detailed geometric shape of thespatial configuration since they array every point in space vertically on the cone’ssurface according to its metric distance from the srcin location. In this way theycan be produced from the plan form without the intervening step of representingcontinuous space as a set of discrete ‘spaces’ (convex, axial, etc.). In point of factthe way these diagrams are produced does involve the subdivision of the plan formof the building into a discrete grid, however the principle of this is that the subdivisioncould be arbitrarily fine and so can be assumed, in the limit, to hold for a continuousrepresentation. Figure 4: Plan of a hypothetical housewith points A and B marked.Figure 5: Space-time cone from a central locationA on plan (viewed from different viewpoints sincethis is a 3D surface)Figure 6: Space-time cone from an isolatedlocation B on plan AB  
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