Brasilia, Brazil, 29 March - 3 April 1999
Reformulating Space Syntax Using Agent-Based Modelling
Michael Batty and Bin Jiang
Central for Advanced Spatial Analysis (CASA)
The Bartlett School of Graduate Studies
(Torrington Place Site)
University College London
Gower Street
London WC1E 6BT
England
tel (44) (0)171 391 1782
fax (44) (0)171 813 2843
email m.batty@ucl.ac.uk
www http://www.casa.ucl.ac.uk/
Representing spaces and the connectivity between them which is the heart
of space syntax has inherent ambiguities which must be resolved if the
method for generating connectivity values is to be automated and generalised.
Equally, ambiguities concerning the use of graph theory to measure such
connectivities must be clarified with respect to the use of planar and/or
syntactical graphs with or without explicit representation of distance.
In this paper, we develop a method in which every point in space is examined
with respect to the visual fields emanating from them. The basic idea
of the reformulated method is to compute the total area seen from every
point, in the associated visual field or isovist. These fields can then
be rank ordered in terms of their area value. Starting with the highest
value, we first generate the field, we then choose the next highest value
which is not in the field just generated and generate the next associated
field. We continue in this way until we exhaust the entire space. The
visual fields overlap and we can immediately see which fields are connected
to one another. We can then produce a connectivity matrix of overlapping
fields and at this point we can compute various various measures of accessibility
on the graph. We propose that the best measure is one in which the farthest
distance seen at each node of the graph - the centre of each visual field
- represents an attractor and the actual distance from this node to a
related node via the area of overlap is used as a deterrence factor. We
then compute access in the same manner as in spatial interaction models.
Finally the computation is done in rather novel terms using agent based
simulation and the results are then displayed in desktop GIS which enables
contour maps of access to be generated. The examples we use are for the
Tate Gallery and for Wolverhampton.
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