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Dear Alan, Could you be as kind as to send us a published (journal) reference which points this out. You see, we've all read enough emails by now. Thank you > -----Original Message----- > From: [log in to unmask] [mailto:[log in to unmask]] On > Behalf Of Alan Penn > Sent: 03 March 2006 14:53 > To: [log in to unmask] > Subject: Re: [SPACESYNTAX] NOT ignore please > > Its funny isn't it? I wonder why people have trouble with this one. > > The RA equation puts mean depth onto a 1-0 scale between the deepest and the > shallowest you could possibly have given that number of nodes in the graph. > This is a normalisation. > > The RRA equation then relativisies this as compared to the mean depth of a > diamond shaped structure with the given number of nodes. This is an > empirical relativisation ie. not particularly 'theory driven' in that it > works statistically in removing the effects of number of nodes in urban > axial graphs from the average mean depth in a system. There are many other > ways that this could be done, and since there is no pre-existing theoretical > assumption built into this process nothing is lost by ding it a different > way. However, it does allow you to compare some properties of graphs between > maps of different sizes on a more or less comparable basis. Something you > certainly cannot do for the unrelativised RA values. > > Alan > > > > > > On 03/03/06, Bin Jiang <[log in to unmask]> wrote: > > > Usually we compare space syntax measures within a same system, not > > > across different systems. This is my perception. Am I wrong? > > > > Well, if you use local integration for a single axial map you *are* > > comparing different systems because the number of nodes involved to > > calculate this measure vary for each node. It is the same if you > > compare global integration between different maps. > > > > Therefore, if you do not agree that RRA / Diamond Shapes provides some > > help... forget the whole thing about local integration... just does > > not work. > > > > For me it is quite OK. > > > > > I am not convinced by the popular saying that the local integration is a > > > good indicator of pedestrian or vehicle flows. Recently I happened to > > > get some vehicle observation datasets with pressure-sensed techniques > > > (so must be very precise observation). I compared the datasets with > > > local integration, and did not end up with a good correlation (R square > > > value about 0.5). > > > > I have got the same in this paper: > > "Continuity lines: aggregating axial lines to predict vehicular > > movement patterns" > > http://www.mindwalk.com.br/papers/ > > > > That is a problem. I produced a continuity map that reveals clearly > > the main street system of my city (Recife, Brazil). But ... correlate > > abstract graph properties with real movement is another issue. There > > are many other factors, such as attractors, street width, etc. > > > > Therefore, this is just a matter what is the number you accept as a > > good proof that the urban grid itself (ignoring the other factors) can > > organise movement patterns. > > > > Regards! > > Lucas Figueiredo > > > > CASA - Centre for Advanced Spatial Analysis > > University College London > > 1-19 Torrington Place > > London WC1E 7HB England > > E-mail: [log in to unmask]