[postgis-users] Find out if polygon is circle

[Martijn Meijers]

> I have many different polygons in my database and would like to know 
> if there's any way to find out if a polygon has the shape of a circle.

You could try to compute compactness for the shapes.

See e.g.

http://gis.stackexchange.com/questions/85812/easily-calculate-roundness-compactness-of-a-polygon

The first answer there mentions:

"""
The compactness of an object is often defined as the area divided by the 
SQUARE of the perimeter. If you multiply this by 4*PI, it will be equal 
to 1 for the circle and this will be the maximum value of your index. 
Any other geometric shape has a smaller ratio.
"""

I think not available in PostGIS, but this seems to be relevant:

http://www.h2gis.org/docs/dev/ST_CompactnessRatio/


Martijn