[OSM-talk] Islands

Artem Pavlenko artem at mapnik.org
Sat Apr 14 13:04:07 BST 2007


On 14 Apr 2007, at 11:45, Lars Aronsson wrote:

> Artem Pavlenko wrote:
>
>> We don't really need all this crossing segments.
>
>> Please, could you explain to me what's wrong with representing
>> features like 'river with islands' as proper polygons (one
>> exterior and n-interior rings) ? If you want just a small part
>> of a bigger polygon for rendering use _clipping_.
>
> How should I map a part of a river or a lake?  If I map a lake,
> but don't have time to map the river flowing into and out of it,
> don't I need to draw a crossing segment where the river enters the
> lake?  Or should I just keep that open?
>
> I have no problem mapping a part of a motorway.  I just do what I
> find time to do, and leave the rest undone.
>

You can use this rule;

Lake represents one feature, should have its own geometry properrty  
(Polygon).

River is another feature. If it's a tiny stream linestring (polyline)  
is appropriate.
For big rivers like Thames use polygon/multipolygon  geometry.

HTH
Cheers,

Artem


>
> -- 
>   Lars Aronsson (lars at aronsson.se)
>   Aronsson Datateknik - http://aronsson.se
>
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Artem Pavlenko
http://mapnik.org



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