Hi Larry,
I don't know if this ratio is often used in geomatics, but I implemented
it in a plugin available on the site :
https://sourceforge.net/projects/jump-pilot/files/p_%20More%20Plugins/OJ%20graph%20toolbox/
I called it circularity and defined it as an integer (where 100 means
perfect circle)
When I did it, my need was to recognize roundabout on a linear network,
so that it does't work only on a polygon layer, but also on a linear
network (where cycles are detected by the JGraphT functions, and
transformed into polygons)
The plugin creates also a few other indicators.
Let me know if it's useful or if it has to be improved for your use-case.
Michaël
Le 27/04/2011 23:00, Larry Becker a écrit :
I had a need to classify polygon shapes into general categories such
as roads and buildings, and I though it might be possible to use a
"thinness" factor calculated using the area and perimeter. After
fooling around with it for a while and not getting the answer, I
goggled and found the following solution:
lCircularity ratio: the ratio of the area of the shape to the area of
a circle (the most compact shape) having the same perimeter.
(area-perimeter ratio)
M = ( 4 * Pi * Area of Polygon) / (Perimeter of Polygon)^2
For a circle, the ratio is one; for a square, it is π / 4; for an
infinitely long and narrow shape, it is zero.
I found it at: http://ce.sharif.edu/~alamgir/
<http://ce.sharif.edu/%7Ealamgir/>
Further searches indicate that this method of classification may be
relatively unknown. Does anyone have knowledge in this area?
regards,
Larry Becker
------------------------------------------------------------------------------
WhatsUp Gold - Download Free Network Management Software
The most intuitive, comprehensive, and cost-effective network
management toolset available today. Delivers lowest initial
acquisition cost and overall TCO of any competing solution.
http://p.sf.net/sfu/whatsupgold-sd
_______________________________________________
Jump-pilot-devel mailing list
Jump-pilot-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
------------------------------------------------------------------------------
WhatsUp Gold - Download Free Network Management Software
The most intuitive, comprehensive, and cost-effective network
management toolset available today. Delivers lowest initial
acquisition cost and overall TCO of any competing solution.
http://p.sf.net/sfu/whatsupgold-sd
_______________________________________________
Jump-pilot-devel mailing list
Jump-pilot-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
