Dear Bin - I think you'll find that your results for segment analysis reflect errors in the spatial data. These commonly arise from the process of creating the segment map in the first place, and typically take the form of discontinuities (a clue is often a red segment linearly connected to a blue one), isolates, and even isolated sub-systems, and these need to be spotted and eliminated one by one or the spatial data will be a mess. I assume, by the way, that you took out stubs up to 40% of the length of line they are on, which wil also affect things ?
Segment angular and axial analysis are very similar, and it isn't mathematically plausible to get high correlations in one case, and zero correlations in the other - let alone for four cases ! - Bill
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Bin Jiang
Sent: 26 October 2014 15:53
To: [log in to unmask]
Subject: Re: [SPACESYNTAX] How to have a 'segment map' in Depth map
Hi, I am not convinced by the segment analysis to be honest. One of my former students conducted a comparison study involving some major space syntax methods including natural streets, axial lines, and segments. It was found through the comparison against social media data (as a good indicator of human activities in streets) that natural streets are the best representation, followed by axial lines, and segments being the worst.
http://hig.diva-portal.org/smash/get/diva2:656758/FULLTEXT01.pdf
Any comments are welcome.
Cheers.
Bin
On 2014/10/26 13:32, SUBSCRIBE SPACESYNTAX Anonymous wrote:
> Thanks Jorge and Bin for your responses. Just to share what I finally get from this discussion and my reading (may not be correct though).
> To do angular analysis using road-centre lines map (or in general):
> - Transform road-centre line map into ‘natural streets’ in ArcMap using Axwomen extension, and produce the ‘axial lines’ based on it (of note, this is totally a new ‘definition’ of axial lines which has been introduced by Xintao Liu and Bin Jiang in a paper entitled “Defining and generating axial lines from street center lines for better understanding of urban morphologies).
> - Export the ‘axial lines’ to MIF.
> - Import MIF into Depthmap, and transform to ‘Axial map’, then transform ‘Axial map’ into ‘segment map’. And, run the angular analysis.
> Of note, in this process, I found the first step to be conceptually really ‘important’; as it is a new definition of Axial lines. Any thought about this step? I mean, ‘how’ we decide about ‘axial lines’. Though, I understand, this is a critical issue in space syntax (and many people criticize us on this!). Professor Bin Jiang already showed in that paper that the new definition of axial lines are more suitable (at a city scale) than the old ones.
> I would be really appreciate it to know how you guys do these steps in
> doing an angular analysis, especially how you define axial lines (you
> draw by hands based on visibility, or you use any auto process, or you
> use the new definition I mentioned above) (maybe this could help to
> reach some consistency among space syntax researchers :) Thanks,
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Bin Jiang
Division of Geomatics, KTH Research School Department of Technology and Built Environment 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/
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European Associate Editor
Computers, Environment and Urban Systems: An International Journal
BinsArXiv: http://arxiv.org/a/jiang_b_1
ICA Commission: https://sites.google.com/site/commissionofica/
Geomatics Program: http://fromto.hig.se/~bjg/geomaticsprogram/
Special Issue: https://sites.google.com/site/call4papersbigdata/
Conference on Social Media: http://research.franklin.uga.edu/iclsm/
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