 |
 |
To quickly reflect on Alan Penn's comments with respect to the issue of comparison : (1) all graph measures are relative to their graphs or contexts; even for degree of connectivity has to be put into its context. For example, in city A, the least connectivity is one, and the most connectivity is 50, while in city B, the least connectivity is one, and the most connectivity is 30. Two streets (one in city A and the other in city B) with the same degree of connectivity of 10 would have different effect in terms of their roles in their individual cities. In this regard, I would suggest derive hierarchy based on head/tail breaks using connectivity, and look at two streets of the same degree of 10 in which hierarchical levels. Let's assume in city A that street of degree 10 is at some middle level, while in city B that street of degree 10 is at the top level. Certainly that street in city B is far more important than that in city A, although both have the same degree 10. https://www.researchgate.net/publication/236627484_Ht-Index_for_Quantifying_the_Fractal_or_Scaling_Structure_of_Geographic_Features (2) following the first point, I think what is super important is ways of thinking. Treating graph measures absolutely is the Euclidean geometric thinking, focusing on individuals, while taking the measures as a relatively indicator is the fractal geometric thinking or a holistic thinking. I have some discussions in this paper with respect to the two ways of thinking: https://www.researchgate.net/publication/282310447_A_Fractal_Perspective_on_Scale_in_Geography Cheers. Bin On 8/31/2016 6:22 PM, Penn, Alan wrote: > 1 - you are right. In fact Bin Jiang is also being somewhat over pessimistic on the issue of comparison, to reduce it only to a matter of the order. The point about space syntax methods are a). the representation is relatively well defined in terms of rigour - the axial map as a map is something that can be used to compare on the same basis different cities. It is sensitive for instant to the relative length and width of streets and allows comparison of the degree to which streets systems are laid out regularly or otherwise. b). the analysis of depth measures (RRA) has been statistically shown to remove the effect of number of lines in the system, and so there is a case that these measures can indeed be used to compare one city to another. This is clearly also the case and somewhat less controversial perhaps, as you point out, for limited radius measures. I would be confident then that the numbers themselves can (within reason) be used to directly compare. > > However there is a major caveat: all cities are different, not only in morphology, but also in a whole range of other criteria that have a functional influence on them; patterns of land use, density, legal and cultural contexts etc. all play a role. So although a morphological variable (e.g.. radius three integration) may be the same for two streets in different cities, this does not mean that the two streets will play the same role in each or that they will function similarly. The exact fact that they are part of a relational system means that they function not only in terms of a specific parameter, but as a part of a complex in which they relate to their neighbours and the neighbours neighbours etc. ad infinitum. > > The question comes down pragmatically for an academic as to why one wishes to compare two different streets in two different cities. So long as you can define appropriately what your intentions are, then it may be possible to define ways of handling the variations between different cities so that you can say whether a specific parameter is significantly different between two streets, or whether the differences are too small to be significant. It really just requires careful thinking. > > 2 - in practice space syntax tools have mostly been applied in interventions in existing cities. Even when these interventions are a part of very large ‘new’ developments, the scale at which syntax works requires us to look at an urban context large enough for the development still to be considered as an intervention. Space syntax can certainly be used to help designers with entirely new green field developments, and in doing that we are of course arguing explicitly from the generic principles gained from understanding other cities (making the comparison question relevant). However, much more powerful are those situations where there is an exiting context that can be observed, where the way that space is used can be interrogated against analysis of the morphology of the existing area, and where proposed design interventions can be inserted into the model and forecast’s made as to their likely effects. Often these are in terms of comparison between the likely effects of different options, and most often the results then iterate with a design team who through the process of analysis learn something about the potentials and constraints of the specific context, and work with their clients, communities and planning regulators, to define better the scope and intention of the scheme and arrive at a better evidenced proposal that has gained buy in from the different stakeholders. > > Although we do use isovist analysis, this is usually a relatively minor part of the process as the things that are more informative are those that extend further in the configuration - the network effects that affect through movement, and the relations between local and global that create intelligibility. > > Alan > > >> On 31 Aug 2016, at 10:05, SUBSCRIBE SPACESYNTAX Anonymous <[log in to unmask]> wrote: >> >> Hi, >> >> Thanks for these insightful comments. >> Two more questions: >> >> 1- As Prof Jiang said: "Given the fact that it is a relative order, it is not good idea to put one street's integration in one city in comparison with another street's integration in another city. Such a comparison is meaningless. In other words, the ranking order makes a good sense only for streets within a same city." >> I'm wondering whether we could compare the integration of a street at 1 KM radius in a city with the integration of another street at 1 KM radius in another city? Conceptually, I don't see any problem, because we limit our analysis to a specific metric value 1KM (so we shouldn't face any 'edge effect'). Any more elaboration on this? My concern would be if space syntax measures are not successful in comparing different cities/form; then they may get criticism that they are 'too' context-specefic. >> 2- On the application of space syntax, I've got the impression (may be wrong) that in the 'existing well-established neighbourhoods', space syntax could be a more useful tool for 'small interventions' . By small interventions, I mean, relocating some small shops, or removing some cul-de-sacs, or even help to locate a new park. While, it could be a tool for 'more radical interventions/changes' for the 'new developments' (to evaluate their plans before they were built). My questions: (a) whether this assumption is correct? (b) if this is correct, then how we could address this comment: "We have only few new developments (maybe less than 5% in the world). The urban form has been already built in many cities. So, how a tool like space syntax which is more efficient for new development, can be advertised as a useful tool for the existing neighbourhoods'. It seems to me that space syntax has been mainly (only) concerned with visual (isoviet analysis) at the neighbourhood scale in the context of existing neighbourhoods. >> >> Anyway, as an academic person, I appreciate and use the concept/method of space syntax in my research. However, as we care about the science (not an architecture/urban design company), we need to be more 'picky' on 'why' we use a method and 'how' such a method may be helpful for the built environment interventions/changes (especially after almost 30 years since it's been invented). >> >> Thanks, >> -- -------------------------------------------------------- Bin Jiang Division of GIScience Faculty of Engineering and Sustainable Development University of Gävle, SE-801 76 Gävle, Sweden Phone: +46-26-64 8901 Fax: +46-26-64 8758 Email: [log in to unmask] Web: http://fromto.hig.se/~bjg/ -------------------------------------------------------- Academic Editor: PLOS ONE Associate Editor: Cartographica BinsArXiv: http://arxiv.org/a/jiang_b_1 Axwoman: http://fromto.hig.se/~bjg/axwoman/ ICA: https://sites.google.com/site/commissionofica/ Geomatics: http://fromto.hig.se/~bjg/geomaticsprogram/ RG: https://www.researchgate.net/profile/Bin_Jiang3 [Högskolan i Gävle] Högskolan i Gävle, 801 76 Gävle • 026 64 85 00 • www.hig.se<http://www.hig.se> För en hållbar livsmiljö för människan University of Gävle, SE-801 76 Gävle, Sweden • +46 (0) 26 64 85 00 • www.hig.se<http://www.hig.se>