[postgis-users] Splitting a Polygon with a Linestring

[Chris Hermansen]

"Some day I hope to get this into JTS/GEOS"...

Go, Martin, go!

Martin Davis wrote:
> That should work.  You may also have the problem of determining which
> of the resultant polygons fell on each side of the drawn line.  The
> usual way to do this would be to run some point-in-polygon queries.
>
> It's amazing how much this use case comes in many different venues
> (PostGIS, GUI tools, etc).  Some day I hope to get this into JTS/GEOS
> as a provided operation, at which point this will be much easier to
> accomplish.
>
> James Beaudoin wrote:
>> I think the steps below will work but I have one question. I am
>> creating an application that allows a user to split a polygon by
>> drawing a linestring across the polygon they wish to change. The
>> crossing linestring has parts that are outside the polygon and I want
>> to remove that before I geomunion. What's the easiest way to do that?
>>
>> - extract the lines that make up the polygon
>> - add to this your crossing linestring
>> - geomunion the lines together.
>> - polygonize the union-ed set
>>
>> Thanks,
>>
>> Jim
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>>
>


-- 
Regards,

Chris Hermansen         mailto:chris.hermansen at timberline.ca
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