That is a complex question that could also be placed on the general
space syntax mailing list, as here we try to address aspects of the QGIS
toolkit in particular.
Nevertheless, I'll try a simple answer...
Global analysis is always radius N: to everywhere. Therefore its results
are the same whatever radius type you use, metric, angular or steps.
Metric type radius can be any value, and there are studies that use
radius from 100m up.
Keep in mind that long segments with more than 2x the radius don't get
any integration value for that radius because you can't get anywhere
The choice of radius must be linked to the research problem and
hypotesis being tested. If your problem relates to pedestrian movement,
400m makes sense as it corresponds to 5 minutes walk, and in much
walkability literature is regarded as a threshold after which the
propensity to walk drops. And if your main focus is the car, then larger
radius make sense. But you might be looking at centrality structures
irrespective of behaviour, then the choice of radius must come from some
In many studies you find very large radius (60km) just because N would
be too slow to calculate in large models.
Steps radius is rarely used in segment analysis. That would be limiting
the range of centrality based on the number of segments (maybe axial
lines, not sure). This is the standard in axial maps as your theory
considers changes of direction. In principle it can be used as long as
your hypothesis is that centrality matters up to a certain number of steps.
Angular type radius is even more rare, and the same principle apply: you
must have a theory or hypothesis to use it. It's also more difficult to
define and understand, as it sets the limit of degrees that you can
turn. These sorts of radii are very irregular, allowing very long
distances (many km) along street alignments, and not going far into
Hope this clarifies things a bit, but as I said, try also the main list
for further insights.
On 22/03/2018 06:44, Jos é Rojas wrote:
> Hi all,
> checking the tutorials on the SS Online Platform I saw that examples use metric radius type and I understand that it could be from 400 to N meters but I want to know if there is a recommended radius for the angular analysis and segment step analysis too. From which radio can a global analysis be differentiated from a local analysis?
> I will appreciate any help.