Dear Martin,
You are completely right, I would expect a high correspondence between
Street Names, Street Category and Continuity lines (if the angle is
not too wide).
The correspondence between maps and the experience while navigating in
cities is an important point:
"As "linear strokes" (Thomson, 2003), continuity lines can be
constructed through an aggregation procedure. However, in the space
syntax context, the observer is not looking at a map to identify
smoothly connected elements. The observer is navigating within a
spatial system and discovers a path through movement" (Figueiredo and
Amorim, 2004, p5)
The problem is that people does not only "reads" the geometry, as you
said, they may well describe directions such as "left or right". I
adopt this second alternative, which is more abstract in my recent
paper:
http://eprints.ucl.ac.uk/archive/00002694/
Please, send yours to me. I am writing my literature review for my PhD
and it would be very useful.
Best Regards,
Lucas Figueiredo
On 31/05/07, Martin Tomko <[log in to unmask]> wrote:
> HI all,
> interesting debate. In our paper (Tomko, M., Winter, S., & Claramunt, C.
> (to appear). Experiential Hierarchies of Streets. Computers, Environment
> and Urban Systems.) we used named streets as we are interested in
> reconstructing the experiential hierarchies of streets, allowing
> strangers to assume what streets their communication partner may know, and
> consecutively refer to them in destination descriptions.
>
> Re continuity lines, I tried to use them in conjunction with the
> "straight"
> direction concept (e.g., Alexander Klippel, Heike Tappe, Lars Kulik, Paul
> U. Lee (2005).Wayfinding Choremes - A Language for Modeling Conceptual
> Route Knowledge. In Journal of Visual Languages and Computing, 16 (4), pp.
> 311–329.) and it works quite nicely. This is one of the few cognitively
> motivated sources of angles I know of usable in this context. The
> correlation of continuity lines with named streets was high, and allowed
> hierarchically higher chunking of streets changing e.g., street type
> (arbitrary choice, such as victoria street changing into Victoria parade
> in Melbourne... it is the "same" street...)
>
> I was wondering, Bin, how/why you selected only 1% of the most central
> streets as the backbone... I still have to reda the paper, I guess.
>
> Martin
>
> > Thanks all for the interesting discussion. Herewith my feedback:
> >
> > The log-log lines are not very straight, and in some case seem pretty
> curved. However the pattern (80/20 partition around the average m) we
> illustrated seems universal. With this pattern we do believe power-law
> there.
> >> but this is curved throughout the length - very clearly so - I suspect
> a
> >> simple power function which would still be interesting...
> >>> One of the problems I had in the Physica A paper was that we do not know
> >>> what a street is. There are several representations out there, but there
> >>> is no uniquely accepted concept?
> >> Agreed - an argument for a (comparatively) well defined concept like
> the
> >> axial line perhaps? :-)
> > Well, I cannot agree with the point. Through the experiments, we see the
> concept of streets based on perceptual grouping is pretty clearly
> defined, much better than axial lines. People may argue that the
> criteria of good continuity is a bit vague. In fact, we tried different
> threshold angles (actually a series from 20 to 90 degrees) for merging
> (or grouping) street segments to form individual streets, and found no
> big change in the illustrated pattern. One of my students Chengke Liu
> has testified three models: axial, stroke, named streets, and found the
> latter two are the best.
> >
> > Cheers.
> >
> > Bin
> >
> > --
> > ------------------------------------------------
> > Bin Jiang
> > Department of Land Surveying and Geo-informatics
> > The Hong Kong Polytechnic University
> > Hung Hom, Kowloon, Hong Kong.
> > Tel: (852) 2766 4335, Fax: (852) 2330 2994
> > Email: [log in to unmask]
> > ------------------------------------------------
> >
>
--
Lucas Figueiredo
http://www.flickr.com/photos/lucasfigueiredo/
Mindwalk
http://www.mindwalk.com.br
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