[postgis-users] Rép: Re: Removing tiny polygons

[Hugues François]

Hello,

In your case, ST_GeometryType() really returns `ST_Polygon' ?

You can have a table with several rows, each one containing a geometry. This geometry can ne a simple one (single entity) or a multi one. 

Hugues

Tom McCallum <termcc at googlemail.com> a écrit :

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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