Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[Martin Koppenhoefer]

sent from a phone

> On 14. Mar 2019, at 09:20, Markus  wrote:
> 
> Unlike a site or multipolygon relation, a
> group relation does *not* constitute a new object, but is merely the
> name of its members as a whole.


actually it does constitute an object, a group, and the fact that there is a 
proper name underlines this. It doesn’t need tags to describe its nature, as 
that is defined through the members.


Cheers, Martin 
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Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[Andy Townsend]

On 13/03/2019 13:59, David Marchal wrote:
I mapped a forest made of several pieces of woodland, some contiguous 
and some isolated, with differents leaf_types. I mapped this 
(https://www.openstreetmap.org/relation/9393253) with a landuse=forest 
multipolygon, with common tags such as name and operator on the 
relation, and with leaf_type tags on the outer members, as each has a 
different value. It seemed a good way to model the fact that these 
woodlands were considered part of the same forest but had differents 
leaf_types, but I am unsure now: the JOSM validator claims that 
contiguous outer members is an error, and openstreetmap.org renders a 
misplaced name and no leaf_type. Is it a modelling failure or a 
renderer and validator error? In the first case, how should I map this?


Using a multipolygon relation like this makes sense when the objects are 
exactly the same, but not when they aren't, so that probably explains 
the validator issue.



Name placement on multipolygons like this is actaully a renderer 
decision - some will use one name per group of trees, some one name 
placed somewhere near the biggest.



I'd probably map your trees as either:


1) natural=wood; name=whatever; operator=whatever; leaf_type=whatever on 
each group of trees.  This will result in duplicated names, but isn't 
that different to the way we split roads when other tags change.



or


2) natural=wood; leaf_type=whatever on each group of trees, and create a 
landuse=forest multipolygon relation with name=whatever; 
operator=whatever that includes each group of trees.



or


3) If the "managed forest area" by operator=whatever includes 
significant area of no trees currently, natural=wood; leaf_type=whatever 
on each group of trees, and create a landuse=forestry multipolygon 
relation with name=whatever; operator=whatever that includes each group 
of trees or no trees managed by the same organisation.



The whole landuse=forest/natural=wood thing is fairly contentious 
though, so please don't take the above as "what everyone does in OSM"; 
it's just how I'd map it.



Best Regards,


Andy


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Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[Markus]

On Thu, 14 Mar 2019 at 01:24, Warin <61sundow...@gmail.com> wrote:
>
> A site relation could be the best solution?

A group relation [1] seems to be the best fit. This is a relation for
a named group of objects. Unlike a site or multipolygon relation, a
group relation does *not* constitute a new object, but is merely the
name of its members as a whole.

[1]: https://wiki.openstreetmap.org/wiki/Proposed_features/Group_Relation

Regards

Markus

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Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[Warin]

On 14/03/19 10:36, Joseph Eisenberg wrote:
Normally we should map features that are “real” and “current”, and is 
easiest to do for things that can be observed in person.


This suggests mapping each patch of trees as a separate polygon or 
closed way, based on having the same leaf_type and leaf_cycle. Usually 
it’s only necessary to use a multipolygon when there is a hole in a 
donut-shaped woodland. Each area should be tagged natural=forest or 
natural=wood in addition to the leaf_type/leaf_cycle tags


+1


So then the problem is, how do you show that all of these patches of 
trees are part of one “forest”?


How can another mapper verify where the named “forest” ends? Is it a 
type of boundary=protected_area that is designated by the local 
government or private landowner? Is there a fence around the whole 
area? It looks like it is not a single continuous area, so this makes 
it even harder to verify where the named forest ends.


A site relation could be the best solution?


I don’t know much about the original poster’s example, but it looks 
like the name is “ Communal Forest”, and the areas 
included in the relation are on separate sides of the village and 
divided by farmland. Also, there are other areas of woodland right 
next to the edge of this forest.


Perhaps this is mapping land ownership parcels rather than a “real” 
physical feature?


-Joseph

On Wed, Mar 13, 2019 at 11:14 PM marc marc > wrote:


Le 13.03.19 à 14:59, David Marchal a écrit :
> the JOSM validator claims that contiguous outer members is an error

yes it's- the sum of all outer should not have a "internal" way
like this one
https://www.openstreetmap.org/relation/9393253#map=17/48.42219/5.92713
so draw a new way for the outer of this part
or split currents ways to include only the outer part in the relation
and make another relation for the leaf_type


> openstreetmap.org  renders a misplaced
name

It doesn't seem so misplaced
https://www.openstreetmap.org/#map=15/48.4222/5.9197
but that's not due to the tag

> no leaf_type

it's hard to render a forêt with several leaf_type
you may put natural=wood landcover=trees to every part of the forêt
having a different leaf_type
but you 'll have a duplicate forest : a foret at the relatin level
and
at every part. currently i'm not aware of a good schema to avoid this
(you can trick some QA tools by using landuse=forest for the
relationship and natural=wook for all parts, but see the wiki for
forest, the meaning of these 2 tags is random/variable depending
on the
mapper, the only meaning you can get is "there are trees", the same
meaning for the 2 tag)


-1. Best not to try and 'trick' things, gets confusing too quickly.

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Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[Joseph Eisenberg]

Normally we should map features that are “real” and “current”, and is
easiest to do for things that can be observed in person.

This suggests mapping each patch of trees as a separate polygon or closed
way, based on having the same leaf_type and leaf_cycle. Usually it’s only
necessary to use a multipolygon when there is a hole in a donut-shaped
woodland. Each area should be tagged natural=forest or natural=wood in
addition to the leaf_type/leaf_cycle tags

So then the problem is, how do you show that all of these patches of trees
are part of one “forest”?

How can another mapper verify where the named “forest” ends? Is it a type
of boundary=protected_area that is designated by the local government or
private landowner? Is there a fence around the whole area? It looks like it
is not a single continuous area, so this makes it even harder to verify
where the named forest ends.

I don’t know much about the original poster’s example, but it looks like
the name is “ Communal Forest”, and the areas included in the
relation are on separate sides of the village and divided by farmland.
Also, there are other areas of woodland right next to the edge of this
forest.

Perhaps this is mapping land ownership parcels rather than a “real”
physical feature?

-Joseph

On Wed, Mar 13, 2019 at 11:14 PM marc marc 
wrote:

> Le 13.03.19 à 14:59, David Marchal a écrit :
> > the JOSM validator claims that contiguous outer members is an error
>
> yes it's- the sum of all outer should not have a "internal" way
> like this one
> https://www.openstreetmap.org/relation/9393253#map=17/48.42219/5.92713
> so draw a new way for the outer of this part
> or split currents ways to include only the outer part in the relation
> and make another relation for the leaf_type
>
>
> > openstreetmap.org renders a misplaced name
>
> It doesn't seem so misplaced
> https://www.openstreetmap.org/#map=15/48.4222/5.9197
> but that's not due to the tag
>
> > no leaf_type
>
> it's hard to render a forêt with several leaf_type
> you may put natural=wood landcover=trees to every part of the forêt
> having a different leaf_type
> but you 'll have a duplicate forest : a foret at the relatin level and
> at every part. currently i'm not aware of a good schema to avoid this
> (you can trick some QA tools by using landuse=forest for the
> relationship and natural=wook for all parts, but see the wiki for
> forest, the meaning of these 2 tags is random/variable depending on the
> mapper, the only meaning you can get is "there are trees", the same
> meaning for the 2 tag)
>
> Regards,
> Marc
>
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Re: [Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[marc marc]

Le 13.03.19 à 14:59, David Marchal a écrit :
> the JOSM validator claims that contiguous outer members is an error

yes it's- the sum of all outer should not have a "internal" way
like this one 
https://www.openstreetmap.org/relation/9393253#map=17/48.42219/5.92713
so draw a new way for the outer of this part
or split currents ways to include only the outer part in the relation
and make another relation for the leaf_type


> openstreetmap.org renders a misplaced name

It doesn't seem so misplaced
https://www.openstreetmap.org/#map=15/48.4222/5.9197
but that's not due to the tag

> no leaf_type

it's hard to render a forêt with several leaf_type
you may put natural=wood landcover=trees to every part of the forêt 
having a different leaf_type
but you 'll have a duplicate forest : a foret at the relatin level and 
at every part. currently i'm not aware of a good schema to avoid this 
(you can trick some QA tools by using landuse=forest for the 
relationship and natural=wook for all parts, but see the wiki for 
forest, the meaning of these 2 tags is random/variable depending on the 
mapper, the only meaning you can get is "there are trees", the same 
meaning for the 2 tag)

Regards,
Marc

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[Tagging] Multipolygon (several outers) forest with different leaf_types: mapping strategy?

[David Marchal]

Hello, there.

I mapped a forest made of several pieces of woodland, some contiguous and some 
isolated, with differents leaf_types. I mapped this 
(https://www.openstreetmap.org/relation/9393253) with a landuse=forest 
multipolygon, with common tags such as name and operator on the relation, and 
with leaf_type tags on the outer members, as each has a different value. It 
seemed a good way to model the fact that these woodlands were considered part 
of the same forest but had differents leaf_types, but I am unsure now: the JOSM 
validator claims that contiguous outer members is an error, and 
openstreetmap.org renders a misplaced name and no leaf_type. Is it a modelling 
failure or a renderer and validator error? In the first case, how should I map 
this?

Awaiting your answers,

Regards.
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