[postgis-devel] RFC - Orientation checking and forcing functions

Sandro Santilli strk at kbt.io
Wed Feb 8 12:17:20 PST 2017


On Wed, Feb 08, 2017 at 03:05:33PM -0500, Daniel Baston wrote:
> The idea was that adding functions with different names would be helpful,
> because "RHR" and "LHR" mean different things to different people (and
> therefore don't mean much of anything.)

In PostGIS "RHR" and "LHR" have well-documented meaning, right ?

> See, for example, the fourth bullet under
> https://tools.ietf.org/html/rfc7946#section-3.1.6

The Wikipedia definition of the rule is about 3d and implies a 3D space,
which is not always the case within PostGIS geometries:
https://en.wikipedia.org/wiki/Right-hand_rule

If you find a name/label which means the same to everybody I'll be
happy to see a wrapper function using it. "Clockwise" for a polygon
with holes doesn't seem to be unambiguous to me (it could for example
mean "all rings are clockwise"...)

--strk;



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