[postgis-users] Removing tiny polygons
Tom McCallum
termcc at googlemail.com
Mon Jan 27 12:29:20 PST 2014
Ok, really silly question now, how can a polygon field contain what looks
like multiple polygons.
So I have a Shapefile of GB but its only got 3 polygons in, according to
PostGis, but there are lots of small island polygons as well which are not
attached to any of the main land masses, so I don't see how they can all
be one polygon? Can a polygon field have multiple polygons in without
being a multi-polygon?
Thanks
On Mon, 27 Jan 2014 19:15:18 -0000, Morten Sickel <morten at sickel.net>
wrote:
> It depends on what you mean with "remove" - do you want to just have the
> large polygons without the area that is covered by the small ones or do
> you want to add the area of the small polygons onto one or more of the
> larges? (e.g. how one typically wants to handle shiver polygons)
>
> In the first case it is as easy as a query like
>
> select the_geom where ST_area(the_geom) > ...
>
> Morten
>
>
> Tom McCallum skrev:
>> Hi all,
>>
>> If I have a polygon geometry field which seems to be made up of a large
>> number of tiny polygons and some larger ones, what is the best way to
>> remove polygons below a certain size? Would I need to preprocess this
>> and
>> save in a new table/record or can I dynamically do it?
>>
>> Thanks
>>
>> Tom
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