Hi all,
This is something I have been pondering about for quite some time: would
it be technically possible to create an option in the PostGIS
"ST_ChaikinSmoothing" function
(https://postgis.net/docs/ST_ChaikinSmoothing.html) to skip smoothing
near perpendicular 90 degrees angles (e.g. within 85-95 degrees?), or
any point who's two connecting segments have a > 90 degree's angle
between them (90-180 degree), and only smooth "sharp" corners of < 90
degrees?
The reason I am asking is that from a cartographer's point of view, you
might not wish to have "square" polygons being smoothed, and there is
also little sense in smoothing angles that are already "smooth" (> 90
degrees).
E.g., natural forests are usually nice features to smooth, especially
after having generalized them which tends to introduce "sharp" corners
and spikes in places. On the contrary, artificial or highly managed
forest tend to be divided into a "square" sections, that should
generally not be smoothed for display in a map.
In addition, although "ST_Subdivide" is generally recommended as the
last step in processing, so after a potential smoothing step, there may
be technical and performance reasons why one would wish to subdivide
earlier in a processing pipeline. If smoothing is subsequently applied
to a subdivided dataset, gaps will appear near the perpendicular
crosspoints of the horizontal and vertical cutting lines of
ST_Subdivide, as these will be smoothed as well.
Of course, this should be an option, not least for the fact that it will
likely also slow down the algorithm due to the additional computations
to be made.
Marco
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