[postgis-devel] ST_GeometrySplit

[George Silva]

Hello guys,

AFAIK, ArcGIS only handles the first case. One geometry splitting another,
even in multiple pieces, in case of the aforementioned C shape linestring.

We should return multiple parts, as many as necessary: example, imagine
multiple "C" shape linestrings concatenated together:

___a________start
|__ b___
___c___|
|__ d___end
     e

In this case we would have 5 parts (I'm not sure if you all can see it...).

Although the splitter line can be as complex as the user wants, it's a
single line.

George


On Wed, Mar 10, 2010 at 7:50 AM, strk <strk at keybit.net> wrote:

> To add more thoughts, there are cases in which also
> a single-segment "blade" against a single linestring
> may return more than 2 parts:
>
>     |
>  +--+---2
>  1|  |
>  +--+---3
>     |
>
> Vertical line above is a single-segment "blade".
> Input is a single C-shaped linestring.
> Numbers represent the components of output.
>
> --strk;
>
>
> On Wed, Mar 10, 2010 at 11:26:34AM +0100, strk wrote:
> > Brain picking you guys about a ST_GeometrySplit.
> >
> > The cases of interest seem to be:
> >  - Split polygon by line
> >  - Split line by line
> >  - Split line by point
> >
> > Initial questions:
> >  - Should we allow multi-segment "blade" lines ?
> >    (where a single polygon or line might be cut in multiple pieces)
> >  - Should we allow multi-component inputs ?
> >    (where the "blade" might cut a single component)
> >
> > Both questions are related to the kind of returned output,
> > that is: should output be always composed by 2 parts or
> > possibly multiple parts ?
> >
> > Comments welcome.
> >
> > --strk;
> >
> >   ()   Free GIS & Flash consultant/developer
> >   /\   http://strk.keybit.net/services.html
>
> --
>
>  ()   Free GIS & Flash consultant/developer
>  /\   http://strk.keybit.net/services.html
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>



-- 
George R. C. Silva

Desenvolvimento em GIS
http://blog.geoprocessamento.net
(34) 9664-3717
(34) 8843-3717
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