[postgis-users] working with multipolygons

[Simon Greener]

Excellent
Have one for me.
You should be able to copy and paste the function at the bottom and it should all work.
Any problems, I'm sure you will let me know.
Simon
On Sat, 09 Oct 2010 16:47:20 +1100, lplateandy <andy at centremaps.co.uk> wrote:

>
> Hi Simon,
>
> Brilliant - exactly what i needed, fully explained and with working examples
> too.
>
> Just need a strong coffee and a bit of patience now...
>
> Andy
>
>
>
> Simon Greener-3 wrote:
>>
>> Andy,
>>
>> Is this of any use to you:
>>
>> http://www.spatialdbadvisor.com/postgis_tips_tricks/92/filtering-rings-in-polygon-postgis
>>
>> regards
>> Simon
>> On Sat, 09 Oct 2010 08:11:24 +1100, lplateandy <andy at centremaps.co.uk>
>> wrote:
>>
>>>
>>> Hi,
>>>
>>> Looking for some tips about the right direction to take when tidying up
>>> some
>>> multi-polygon data. I
>>> have lots of 2 by 2 kilometre chunks defining a type of coverage.
>>>
>>> The information for each 2 by 2km chunk has been merged into
>>> multi-polygons,
>>> it may have holes as small as 25 by 25 metres or equally the area may
>>> only
>>> be partly filled along with little 25 by 25 metre islands.
>>>
>>> Is there a method to delete parts of a multi-polygon for example:
>>>
>>> 1) Any elements which represent a hole
>>> 2) Any elements below a certain threshold size
>>>
>>> I can imagine that dissolving the multi-polygon would allow me to apply
>>> changes to the islands but am not sure about the holes
>>>
>>>
>>> I also found that when i tried to carry out some queries such as
>>> ST_SimplifyPreserveTopology or ST_Envelope i get null areas or bounding
>>> boxes of just one of the holes - as though the action is just being
>>> applied
>>> to one of the elements in the polygon - perhaps the first one - is that
>>> the
>>> case?
>>>
>>>
>>> Any pointers to get me started would be much appreciated.
>>>
>>> Thanks in advance
>>>
>>> Andy
>>
>>
>> --
>> SpatialDB Advice and Design, Solutions Architecture and Programming,
>> Oracle Database 10g Administrator Certified Associate; Oracle Database 10g
>> SQL Certified Professional
>> Oracle Spatial, SQL Server, PostGIS, MySQL, ArcSDE, Manifold GIS, FME,
>> Radius Topology and Studio Specialist.
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>


-- 
SpatialDB Advice and Design, Solutions Architecture and Programming,
Oracle Database 10g Administrator Certified Associate; Oracle Database 10g SQL Certified Professional
Oracle Spatial, SQL Server, PostGIS, MySQL, ArcSDE, Manifold GIS, FME, Radius Topology and Studio Specialist.
39 Cliff View Drive, Allens Rivulet, 7150, Tasmania, Australia.
Website: www.spatialdbadvisor.com
   Email: simon at spatialdbadvisor.com
   Voice: +61 362 396397
Mobile: +61 418 396391
Skype: sggreener
Longitude: 147.20515 (147° 12' 18" E)
Latitude: -43.01530 (43° 00' 55" S)
GeoHash: r22em9r98wg
NAC:W80CK 7SWP3