Another multipolygon question

classic Classic list List threaded Threaded
50 messages Options
123
Reply | Threaded
Open this post in threaded view
|

Another multipolygon question

AlaskaDave
Another situation that occurs quite frequently in my mapping (in Alaska especially), is when an island defined by natural=coastline is also covered right to the water with natural=wood. Usually, I duplicate the coastline, shrink it a bit, and then tag it with natural=wood. But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure.
,
The island is at 58.56588, -152.59579 and the relation ID=8828482

What do you think is the best approach to handle this situation?

Dave

--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

dieterdreist


sent from a phone

> On 20. Oct 2018, at 11:38, Dave Swarthout <[hidden email]> wrote:
>
> But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure


I also do this, for example if there’s a fence but I also want to tag the area it delimits. Or for buildings and things that are there, in some cases.


Cheers, Martin
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
Not only legitimate,  but recommended! 

If you haven't stumbled on it yet, another useful procedure is to map areas of landuse use or landcover by drawing each border only once, and having each area be a multipolygon with the shared border way as a member. With that approach there's no need to retrace an irregular boundary. You just add it to the multipolygon on either side.

For an example, look at West Point. https://www.openstreetmap.org/relation/175474 and how the shared ways with the parks, cemeteries, golf courses, and so on are handled. It means that even simple areas like https://www.openstreetmap.org/relation/7084917 become multipolygons, but it ensures that the boundaries all stay consistent, because you need to map each one only once.

On Sat, Oct 20, 2018, 06:22 Martin Koppenhoefer <[hidden email]> wrote:


sent from a phone

> On 20. Oct 2018, at 11:38, Dave Swarthout <[hidden email]> wrote:
>
> But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure


I also do this, for example if there’s a fence but I also want to tag the area it delimits. Or for buildings and things that are there, in some cases.


Cheers, Martin
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

marc marc
> create a single-member multipolygon from the coastline way  
> and then tag the resultant relation with natural=wood

I often put the natural=wood on the inner way itself
it's not working for some apps/render style ?
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
It conflicts with natural=coastline

On Sat, Oct 20, 2018, 10:36 marc marc <[hidden email]> wrote:
> create a single-member multipolygon from the coastline way 
> and then tag the resultant relation with natural=wood

I often put the natural=wood on the inner way itself
it's not working for some apps/render style ?
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Mark Wagner
In reply to this post by Kevin Kenny-3
On Sat, 20 Oct 2018 09:49:57 -0500
Kevin Kenny <[hidden email]> wrote:

> Not only legitimate,  but recommended!
>
> If you haven't stumbled on it yet, another useful procedure is to map
> areas of landuse use or landcover by drawing each border only once,
> and having each area be a multipolygon with the shared border way as
> a member. With that approach there's no need to retrace an irregular
> boundary. You just add it to the multipolygon on either side.

Works great, right up until you need to maintain it.  So, you've got
your "natural=wood" multipolygon sharing a way with an adjoining
"natural=scrub".  And then, some inconsiderate developer bulldozes his
way across the boundary and puts up a housing development.  Now what do
you do?  You can't unglue the boundary and shrink the two affected
areas to make room for the "landuse=residential" because there's only
one way.

The only option I've found is to remove the affected section of
boundary from one of the multipolygons, move it to the new location,
create a new boundary way for the other multipolygon in the proper
place and add it, create a new multipolygon for the development and add
the relevant boundary ways to it, and then confirm that you haven't
broken any of the multipolygons involved.  It's painful enough that
it's usually faster and easier just to delete everything and re-create
them from scratch as ordinary closed ways.

--
Mark

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

AlaskaDave
Wow, the West Point and the Hudson Highlands State Park multipolygons are impressive and yes, I see how using multipolygons has made it simpler. Except if, as Mark points out, one of the boundaries changes and then it's going to be an awful mess to fix. In my particular use case, it's highly unlikely that developers will move anything seeing as most of my Alaska work is in country so wild I'll never see any of it in my lifetime. But I can certainly appreciate the difficulty in changing a beast like that.

On some of the larger islands where there are areas without trees I'll use the coastline way as a border by clicking along it and using (F)ollow in JOSM thus using those nodes for two purposes. When a clearing or beach occurs I simply move off the coastline, trace around the clear area, and then rejoin the coastline way. Then later, if adjustments need to be made I can simply unglue the wood area nodes where I need to.

As for Warin's comment, I'm not sure it makes any difference as to which of natural=wood or natural=coastline gets tagged at top level. Unless, of course, the coastline is already a multipolygon.

Opinions?

On Sun, Oct 21, 2018 at 2:12 AM Mark Wagner <[hidden email]> wrote:
On Sat, 20 Oct 2018 09:49:57 -0500
Kevin Kenny <[hidden email]> wrote:

> Not only legitimate,  but recommended!
>
> If you haven't stumbled on it yet, another useful procedure is to map
> areas of landuse use or landcover by drawing each border only once,
> and having each area be a multipolygon with the shared border way as
> a member. With that approach there's no need to retrace an irregular
> boundary. You just add it to the multipolygon on either side.

Works great, right up until you need to maintain it.  So, you've got
your "natural=wood" multipolygon sharing a way with an adjoining
"natural=scrub".  And then, some inconsiderate developer bulldozes his
way across the boundary and puts up a housing development.  Now what do
you do?  You can't unglue the boundary and shrink the two affected
areas to make room for the "landuse=residential" because there's only
one way.

The only option I've found is to remove the affected section of
boundary from one of the multipolygons, move it to the new location,
create a new boundary way for the other multipolygon in the proper
place and add it, create a new multipolygon for the development and add
the relevant boundary ways to it, and then confirm that you haven't
broken any of the multipolygons involved.  It's painful enough that
it's usually faster and easier just to delete everything and re-create
them from scratch as ordinary closed ways.

--
Mark

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging


--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
In reply to this post by Mark Wagner
Works great, right up until you need to maintain it.  So, you've got
your "natural=wood" multipolygon sharing a way with an adjoining
"natural=scrub".  And then, some inconsiderate developer bulldozes his
way across the boundary and puts up a housing development.  Now what do
you do?  You can't unglue the boundary and shrink the two affected
areas to make room for the "landuse=residential" because there's only
one way.

The only option I've found is to remove the affected section of
boundary from one of the multipolygons, move it to the new location,
create a new boundary way for the other multipolygon in the proper
place and add it, create a new multipolygon for the development and add
the relevant boundary ways to it, and then confirm that you haven't
broken any of the multipolygons involved.  It's painful enough that
it's usually faster and easier just to delete everything and re-create
them from scratch as ordinary closed ways.

I actually do edit those things pretty routinely. It involves redrawing only for the added ways.

Draw the new closed polygon representing the landuse=residential. Make it a multipolygon immediately.

Insert nodes at the intersections of this closed way with the existing ways (if you didn't draw it that way to start with). Split the old and new ways on the nodes. (Splitting is safe - they're multipolygons already.) JOSM has an 'add nodes at intersections' feature that helps with this.

Edit each of the old multipolygons to replace their old boundaries with the new ones. That's just 'remove the old ways, insert the new ones' in the relation editor.

Finally, delete any ways that are now unused.

I can do this *lots* faster than I can redraw an irregular boundary, at least in JOSM. (I'm not skilled enough with iD to comment. it wasn't much harder in Meerkartor when I tried it.) 



_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Warin
On 21/10/18 12:24, Kevin Kenny wrote:
Works great, right up until you need to maintain it.  So, you've got
your "natural=wood" multipolygon sharing a way with an adjoining
"natural=scrub".  And then, some inconsiderate developer bulldozes his
way across the boundary and puts up a housing development.  Now what do
you do?  You can't unglue the boundary and shrink the two affected
areas to make room for the "landuse=residential" because there's only
one way.

The only option I've found is to remove the affected section of
boundary from one of the multipolygons, move it to the new location,
create a new boundary way for the other multipolygon in the proper
place and add it, create a new multipolygon for the development and add
the relevant boundary ways to it, and then confirm that you haven't
broken any of the multipolygons involved.  It's painful enough that
it's usually faster and easier just to delete everything and re-create
them from scratch as ordinary closed ways.

I actually do edit those things pretty routinely. It involves redrawing only for the added ways.

Draw the new closed polygon representing the landuse=residential. Make it a multipolygon immediately.

Insert nodes at the intersections of this closed way with the existing ways (if you didn't draw it that way to start with). Split the old and new ways on the nodes. (Splitting is safe - they're multipolygons already.) JOSM has an 'add nodes at intersections' feature that helps with this.

Edit each of the old multipolygons to replace their old boundaries with the new ones. That's just 'remove the old ways, insert the new ones' in the relation editor.

Finally, delete any ways that are now unused.

I can do this *lots* faster than I can redraw an irregular boundary, at least in JOSM. (I'm not skilled enough with iD to comment. it wasn't much harder in Meerkartor when I tried it.) 



An area of sand I introduced .. between a natural coastline, a tree area and a water area... Relation: 8718211. Using JOSM.
Yes the coastline was already a relation, as was the tree area.. I don't remember what the water areas was.. probably a relation too.

Most, if not all, the coastlines I deal with are relations.

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

bkil
In reply to this post by Kevin Kenny-3
It seems many would find a short video tutorial depicting these steps very handy. Would you mind sharing on Bitchute or on some other video hosting site?

On Sun, Oct 21, 2018 at 3:26 AM Kevin Kenny <[hidden email]> wrote:
Works great, right up until you need to maintain it.  So, you've got
your "natural=wood" multipolygon sharing a way with an adjoining
"natural=scrub".  And then, some inconsiderate developer bulldozes his
way across the boundary and puts up a housing development.  Now what do
you do?  You can't unglue the boundary and shrink the two affected
areas to make room for the "landuse=residential" because there's only
one way.

The only option I've found is to remove the affected section of
boundary from one of the multipolygons, move it to the new location,
create a new boundary way for the other multipolygon in the proper
place and add it, create a new multipolygon for the development and add
the relevant boundary ways to it, and then confirm that you haven't
broken any of the multipolygons involved.  It's painful enough that
it's usually faster and easier just to delete everything and re-create
them from scratch as ordinary closed ways.

I actually do edit those things pretty routinely. It involves redrawing only for the added ways.

Draw the new closed polygon representing the landuse=residential. Make it a multipolygon immediately.

Insert nodes at the intersections of this closed way with the existing ways (if you didn't draw it that way to start with). Split the old and new ways on the nodes. (Splitting is safe - they're multipolygons already.) JOSM has an 'add nodes at intersections' feature that helps with this.

Edit each of the old multipolygons to replace their old boundaries with the new ones. That's just 'remove the old ways, insert the new ones' in the relation editor.

Finally, delete any ways that are now unused.

I can do this *lots* faster than I can redraw an irregular boundary, at least in JOSM. (I'm not skilled enough with iD to comment. it wasn't much harder in Meerkartor when I tried it.) 


_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

bkil
In reply to this post by dieterdreist
I've seen many usages of tagging the area as desired (restaurant, playground, etc.) and then only adding the extra tag barrier=fence on it to mean that the area is surrounded by a fence. It renders perfectly, although I'm not sure if this is a preferred notation, as it is not discussed on the wiki.

The infobox on the right does prohibit usage on areas, but I'm not sure what kind of consideration went into deciding this. Jojo4u introduced this restriction on 2015-03-27T21:56 with comment "not defined as an area":

It was not mentioned in the original proposal:

However it was brought up on the talk page in 2008:

And anyway such documentation can become out of date, so my question is whether this notation is viable?


On Sat, Oct 20, 2018 at 1:22 PM Martin Koppenhoefer <[hidden email]> wrote:


sent from a phone

> On 20. Oct 2018, at 11:38, Dave Swarthout <[hidden email]> wrote:
>
> But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure


I also do this, for example if there’s a fence but I also want to tag the area it delimits. Or for buildings and things that are there, in some cases.


Cheers, Martin
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

AlaskaDave
I was wishing that someone would write a short tutorial about relations, the various concepts about tagging them, and problem solving when something goes wrong with one. I have been unable to understand with any degree of certainty how and why we create them, which is the reason I started this thread and contributed to the other one about tagging groups of lakes. The Wiki is helpful but leaves out a lot of details. A tutorial, video or otherwise, would be extremely helpful.

I'm certainly unable to create such a help page or tutorial but someone with more experience should. I use relations often but when one develops an error, I'm usually hard pressed to fix it. As OSM becomes ever more sophisticated the learning curve gets steeper and mappers, especially beginners, will make tons of errors when using relations and won't have any idea how to go about fixing them.

Dave

On Sun, Oct 21, 2018 at 6:50 PM bkil <bkil.hu+[hidden email]> wrote:
I've seen many usages of tagging the area as desired (restaurant, playground, etc.) and then only adding the extra tag barrier=fence on it to mean that the area is surrounded by a fence. It renders perfectly, although I'm not sure if this is a preferred notation, as it is not discussed on the wiki.

The infobox on the right does prohibit usage on areas, but I'm not sure what kind of consideration went into deciding this. Jojo4u introduced this restriction on 2015-03-27T21:56 with comment "not defined as an area":

It was not mentioned in the original proposal:

However it was brought up on the talk page in 2008:

And anyway such documentation can become out of date, so my question is whether this notation is viable?


On Sat, Oct 20, 2018 at 1:22 PM Martin Koppenhoefer <[hidden email]> wrote:


sent from a phone

> On 20. Oct 2018, at 11:38, Dave Swarthout <[hidden email]> wrote:
>
> But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure


I also do this, for example if there’s a fence but I also want to tag the area it delimits. Or for buildings and things that are there, in some cases.


Cheers, Martin
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging


--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Mateusz Konieczny-3
21. Oct 2018 14:58 by [hidden email]:

I was wishing that someone would write a short tutorial about relations, the various concepts about tagging them, and problem solving when something goes wrong with one. I have been unable to understand with any degree of certainty how and why we create them, which is the reason I started this thread and contributed to the other one about tagging groups of lakes.


I thought about doing something like that, but my main reason why I avoided that is


- I am not sure what exactly is unclear for other

- I was dubious whatever my work would be noticed by people who would need it

 

The Wiki is helpful but leaves out a lot of details. A tutorial, video or otherwise, would be extremely helpful.


Maybe improving wiki would be a good idea as the first steep.


Can you get example of specific problems that you encountered and wiki pages where

you tried to dind an answer?


_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Mateusz Konieczny-3
In reply to this post by AlaskaDave
Is forest starting immediately on the water edge or is there a beach/marsh/whatever between
water and forest?

With shoreline as border of both water and forest it is OK to reuse it, if there is - even
currently unmapped - feature between them then reusing ways is only going to make
life of future mappers more irritating.

20. Oct 2018 11:38 by [hidden email]:

Another situation that occurs quite frequently in my mapping (in Alaska especially), is when an island defined by natural=coastline is also covered right to the water with natural=wood. Usually, I duplicate the coastline, shrink it a bit, and then tag it with natural=wood. But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure.
,
The island is at 58.56588, -152.59579 and the relation ID=8828482

What do you think is the best approach to handle this situation?

Dave

--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
I'm somewhat familiar with a couple of places that Alaska Dave has mapped, and they're the sort of places where the shoreline must be mapped from winter, 'leaves down' aerials, because otherwise the shoreline is obscured by overhanging trees and matted aquatic vegetation.

On Sun, Oct 21, 2018, 13:42 Mateusz Konieczny <[hidden email]> wrote:
Is forest starting immediately on the water edge or is there a beach/marsh/whatever between
water and forest?

With shoreline as border of both water and forest it is OK to reuse it, if there is - even
currently unmapped - feature between them then reusing ways is only going to make
life of future mappers more irritating.

20. Oct 2018 11:38 by [hidden email]:

Another situation that occurs quite frequently in my mapping (in Alaska especially), is when an island defined by natural=coastline is also covered right to the water with natural=wood. Usually, I duplicate the coastline, shrink it a bit, and then tag it with natural=wood. But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure.
,
The island is at 58.56588, -152.59579 and the relation ID=8828482

What do you think is the best approach to handle this situation?

Dave

--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Graeme Fitzpatrick
In reply to this post by Mateusz Konieczny-3


On Mon, 22 Oct 2018 at 03:24, Mateusz Konieczny <[hidden email]> wrote:

Can you get example of specific problems that you encountered 

 
As mentioned once before, I'm with Dave! :-)

Please start with the absolute basics - when & why should you use a relation, then how do you actually do it.

Thanks

Graeme
 

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

dieterdreist
In reply to this post by bkil


sent from a phone

> On 21. Oct 2018, at 13:50, bkil <[hidden email]> wrote:
>
> I've seen many usages of tagging the area as desired (restaurant, playground, etc.) and then only adding the extra tag barrier=fence on it to mean that the area is surrounded by a fence. It renders perfectly, although I'm not sure if this is a preferred notation, as it is not discussed on the wiki.


there is a property, fenced=yes, which can be added to a fenced area. For barrier=fence the object is expected to be a linear way (could be closed).

The fenced=yes property is currently declared deprecated by the wiki.

Cheers,
Martin
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Warin
In reply to this post by Kevin Kenny-3
Err .. in some places .. 'leaves down' does not occur :)


On 22/10/18 04:59, Kevin Kenny wrote:
I'm somewhat familiar with a couple of places that Alaska Dave has mapped, and they're the sort of places where the shoreline must be mapped from winter, 'leaves down' aerials, because otherwise the shoreline is obscured by overhanging trees and matted aquatic vegetation.

On Sun, Oct 21, 2018, 13:42 Mateusz Konieczny <[hidden email]> wrote:
Is forest starting immediately on the water edge or is there a beach/marsh/whatever between
water and forest?

With shoreline as border of both water and forest it is OK to reuse it, if there is - even
currently unmapped - feature between them then reusing ways is only going to make
life of future mappers more irritating.

20. Oct 2018 11:38 by [hidden email]:

Another situation that occurs quite frequently in my mapping (in Alaska especially), is when an island defined by natural=coastline is also covered right to the water with natural=wood. Usually, I duplicate the coastline, shrink it a bit, and then tag it with natural=wood. But yesterday I tried something new, new for me anyway, and that was to create a single-member multipolygon from the coastline way and then tag the resultant relation with natural=wood in order to reduce the number of nodes used. I was pleased that JOSM didn't complain and that the island seemed to render okay but I'm not sure this is a legitimate procedure.
,
The island is at 58.56588, -152.59579 and the relation ID=8828482

What do you think is the best approach to handle this situation?

Dave

--
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging


_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging



_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
On Sun, Oct 21, 2018 at 6:46 PM Warin <[hidden email]> wrote:
Err .. in some places .. 'leaves down' does not occur :)

Yes. However, the fact that "leaves down" images are needed in *those* particular places to distinguish forest from water strongly suggests that there isn't another area in between the two.

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
Reply | Threaded
Open this post in threaded view
|

Re: Another multipolygon question

Kevin Kenny-3
In reply to this post by AlaskaDave
On Sun, Oct 21, 2018 at 7:34 AM bkil <bkil.hu+[hidden email]> wrote:
It seems many would find a short video tutorial depicting these steps very handy. Would you mind sharing on Bitchute or on some other video hosting site?

On Sun, Oct 21, 2018 at 9:00 AM Dave Swarthout <[hidden email]> wrote:
I was wishing that someone would write a short tutorial about relations, the various concepts about tagging them, and problem solving when something goes wrong with one. I have been unable to understand with any degree of certainty how and why we create them, which is the reason I started this thread and contributed to the other one about tagging groups of lakes. The Wiki is helpful but leaves out a lot of details. A tutorial, video or otherwise, would be extremely helpful.

On Sun, Oct 21, 2018 at 1:24 PM Mateusz Konieczny <[hidden email]> wrote:
Maybe improving wiki would be a good idea as the first [step].
 
I find that video tutorials don't often fit my learning style, so I don't often use them and have never made one. Moreover, I'm an old man and somewhat set in my ways. Nevertheless, they seem to be demanded, and if nobody else steps forward, perhaps it will be possible to teach this old dog that new trick.  I'd be willing to take a whack at a written tutorial, but can't promise any particular time frame. Just at the moment, I'm chronically busy.  

The right place might be the Wiki, but I've two reservations. First, I've simply burnt my fingers too many times when touching a Wikipedia page. Perhaps this community is a trifle less fiery? Second, what I've seen on OSM's Wiki (as well as Wikipedia and others) is that editors jump in to add details that make the presentation more "correct," but less approachable to a newcomer. For an introductory tutorial, this drift is disastrous, because introductory material frequently is in the form of a "lie to children" https://en.wikipedia.org/wiki/Lie-to-children that is not techinically accurate, but provides enough of a mental model to do simple things and prepares the mind to accept a more complete explanation later.

One thing that I will surely not be able to accomplish is to ferret out all the obsolete and misleading information about relations that there is on the Wiki. The community has had a complex history of groping toward a theory of relations as it stands today, with several false paths along the way. For example, I'm pretty sure that there are still Wiki pages out there advising to place the tags that belong to a multipolygon on the (presumed unique) outer ring. Moreover, there is bound to be similar groping in the future as we grapple with representing ever more complex things, e.g., "traffic must stop at this intersection, except for right-turning traffic in the rightmost lane, which need only give way to conflicting traffic," or "this parking field is exclusively for the use of these three stores, all of which are some distance down the street, not contiguous with it."

Nevertheless, there are particular relations that are surrounded by considerably less remaining controversy and supported by extensive usage. Among these are multipolygons, administrative boundaries (really a special case of multipolygons, but we got there by a different path), waterways (again, a special case of multipolygons, and this time, multipolygons provide an acceptable alternative), and routes (bus, road, hiking, cycling, etc.)  A tutorial or series of tutorials could certainly cover these relations and leave the fine details, about which we quite rightly love to argue, to a more advanced student.

I'm certainly unable to create such a help page or tutorial but someone with more experience should. I use relations often but when one develops an error, I'm usually hard pressed to fix it. As OSM becomes ever more sophisticated the learning curve gets steeper and mappers, especially beginners, will make tons of errors when using relations and won't have any idea how to go about fixing them.

 If I were to take on this task (again, no guarantees about the time frame), I could certainly address this issue with JOSM (and possibly Meerkartor). I surely do not know Potlatch2, iD, or any other tool well enough to manage anything but the simplest of relations in it, nor do I see obvious things in the UI that would do what I need. It may well be limitations of the tools, rather than limitations of knowledge and training, that make people assert that relations are unmaintainable or that drawing complex boundaries twice is easier than creating multipolygons with shared ways. That last statement, however, may be nothing but a base libel based on ignorance. In that case, I'm more than willing to be enlighened. It would occasionally be handy to be able to make a quick change to a multipolygon when I'm away from a machine that has my preferred tools and simply working in a browser.

_______________________________________________
Tagging mailing list
[hidden email]
https://lists.openstreetmap.org/listinfo/tagging
123