[postgis-devel] ST_GeometrySplit

[Martin Davis]

Not really...  all I can think of to do in this case is to choose one or 
other direction as primary, and return ambiguous cases as that 
direction.  Really it has to be up to the user to provide reasonable 
input - you can't expect to give a sensible answer to a nonsensical 
question.

strk wrote:
> On Wed, Mar 10, 2010 at 11:49:18AM -0800, Chris Hodgson wrote:
>
>   
>> Right-side vs left side can be ambiguous too... an example is a circle 
>> or spiral that is split by a line on only one side.
>>     
>
> Argh, you're right. Here's a simple example:
>
>
>     +-------+ 
>     |   ^   |
>     |   |   |
>     |  ?|R  |
>     +-----> |
>         |   |
>        L|?  |
>   IN -------+
>         |
>        CUT
>
> I marked with 'L' the part which is on the Left and with R
> the part which is on the Right of the cut line.
> The question mark is for the part which is both
> on the Right (lower intersection point)
> *and* on the Left (higher intersection point).
>
> Maybe Martin has some neat topological rabit in his hat ?
>
>
> --strk; 
>
>   ()   Free GIS & Flash consultant/developer
>   /\   http://strk.keybit.net/services.html
>
>   

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022