Re: [Talk-ht] River ways : How to treat Duplicates

[Pierre Beland]

Thanks to Olaf and David for their explanations.

Pierre Béland
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Re: [Talk-ht] River ways : How to treat Duplicates

[Olaf Hasemann]

Hello,

just to make the second method discribed by David a little bit more concrete:

You model the riverbank (some say riverbed) with the island as a hole.
At least the outer bound (way/ways) is tagged with waterway=riverbank,
or you can tag the whole relation (multipolygon).

You can use several ways for discribing the bounds as long as they are
connected. Details can be found here: 

http://wiki.openstreetmap.org/wiki/Multipolygon

In any way the 'main' river way should be kept in addition to the riverbank.

regards
Olaf Hasemann

Am Montag, 22. Februar 2010 13:05 schrieb David Groom:
> Pierre
>
> These additional ways are not duplicates, as they do not follow the same
> path as the main river.  If you delete the shorter ways then the islands
> will "disappear" from the map.
>
> There are two possible methods of mapping these islands.
>
> 1) the simple method, which has been used in your example, where the main
> river is drawn as one way, and the path of the river round an island is
> drawn as another way.
>
> 2) use areas and relations,  here the main "outside of the river" would be
> drawn as one way, the island would be drawn as another way, and both would
> be added to a multipolygon relation.
>
> David
>
>   - Original Message -
>   From: Pierre Beland
>   To: talk-ht@openstreetmap.org
>   Sent: Monday, February 22, 2010 2:09 AM
>   Subject: [Talk-ht] River ways : How to treat Duplicates
>
>
>
>
>   Before deleting duplicate ways for rivers, I want your advice.
>
>   For Example, Les Trois Rivières, way=49375347 is the main river way. But
> we also find few ways that trace a second route around islands : ways
> 48392811, 48392826, 48475427, 48475510, 48475442, 48474646, 48476419,
> 48474401, 48477201, 48474784, 48475251. Should these segments be considered
> as duplicates and deleted
>
>
>   Pierre Beland
>
>
>
> ---
>---
>
>
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Re: [Talk-ht] River ways : How to treat Duplicates

[David Groom]

Pierre

These additional ways are not duplicates, as they do not follow the same path 
as the main river.  If you delete the shorter ways then the islands will 
"disappear" from the map.

There are two possible methods of mapping these islands.

1) the simple method, which has been used in your example, where the main river 
is drawn as one way, and the path of the river round an island is drawn as 
another way.

2) use areas and relations,  here the main "outside of the river" would be 
drawn as one way, the island would be drawn as another way, and both would be 
added to a multipolygon relation.

David
 
  - Original Message - 
  From: Pierre Beland 
  To: talk-ht@openstreetmap.org 
  Sent: Monday, February 22, 2010 2:09 AM
  Subject: [Talk-ht] River ways : How to treat Duplicates




  Before deleting duplicate ways for rivers, I want your advice.

  For Example, Les Trois Rivières, way=49375347 is the main river way. But we 
also find few ways that trace a second route around islands : 
  ways 48392811, 48392826, 48475427, 48475510, 48475442, 48474646, 48476419, 
48474401, 48477201, 48474784, 48475251.  
  Should these segments be considered as duplicates and deleted


  Pierre Beland



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