Multipolygon of fence, building, fence, building, car parking

Question

Hi,

I want to map a Lumber shop business. Its outer boundaries are defined by:

a fence in the west and north west side
a building in the north side
a car parking in the north east, east and south east side
a building in the south side
a fence in the south side
and another building in the south side

I can't find the best way to represent such configuration. I tried creating a multipolygon relation but it fails to "link" those members together. Any suggestion ? Should I use a "site" relation?

For the curious ones, here is the case: http://www.openstreetmap.org/edit?editor=id#map=19/35.91258/-79.07332

Thanks.

Accepted Answer

What you need is to draw a simple polygon (closed way) surrounding the facility and add the tags qualifying the shop onto this polygon with e.g. "shop=lumber" + "name=name_of_the_shop". When you draw this polygon, you might have to reuse existing nodes created for the fences and buildings. Hence the fence will partially overlap with the surrounding polygon but this is not a problem if this is physically the case. (see this school example from the wiki)
Later, you can improve the map by specifying which building is doing what (warehouse, office, etc) on each building polygon.
The "multipolygon" relation is only required for complex geometries (with inners/outers) or very big polygons (a way is limited to 2000 nodes in OSM).
A "site" relation is only required when a single area is not possible. For instance, a university is often spread on multiple locations in a town/city.

Answer 2

0

Like always in OSM, there is not one single 'best' way that fits for every scenario ;) , so I just will try to present a few that IMHO might make sense:

No Multipolygon
In your case, I don't see an advantage to make use of a relation to group all things together (beside that it would be semantical correct). So what I usually do is to map the biggest area (here the fence) with the POI properties and keep all the others as they are. If you like, you can tag the buildings more detailed.
Site-relation
As you already wrote, a site relation is a common way to group things together, but AFAIK it's more used for keeping distributed sites together (as a university campus that is spread over the city etc.). AFAIK there is currently no tool/service that makes use of this relation.

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answered 16 Dec '13, 07:31

iii
4.9k●8●40●82
accept rate: 10%

Thanks for your answer. That is helpful. However I've some questions:

No Multipolygon

Do you mean I should extend the fence to cover the entire area ? the problem is that there is no fence over the entire area so it would not be correct. If I don't extend the fence, then how would we know that the parking belongs to the store ?

Site-relation

If no tool/service that makes use of this relation, how come is it a "common" way to group things together ?

(16 Dec '13, 12:14) exxos

This is a case for a multipolygon, because there is not a fence all around it, so you have to use several outer ways to form together one outline. Also if the fence was all around it, it would be better to use a multipolygon, as a fence is a linear (and distinct feature) and should not be tagged on the same object as the area inside it.

(18 Dec '13, 12:47) dieterdreist

If you wanted to do the latter (tag the fence on the area) the way to do it would be to keep the fence untagged (as it is a linear way) and add the attribute "fenced=yes" to the area, but this is not possible here because you don't have a continuous fence (and 2 different mapping styles for the same thing are not desirable anyway). KISS.

(18 Dec '13, 12:48) dieterdreist

Answer 3

0

Hi take a look at a university or school area, https://help.openstreetmap.org/questions/5148/mapping-a-university-campus. Or just draw a complete way around the area and ad a name tag, without building a multipolygone like iii stated.

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answered 16 Dec '13, 07:36

Hendrikklaas
9.3k●207●238●387
accept rate: 5%

Answer 4

-1

If you want to avoid overlapping ways, which happens in Pieren's case, then you can draw single ways which you chain up as needed with a multipolygon (like you described in your question). Likely you just did something wrong (e.g. no closed multipolygon outer way). However, this does not help for pieces of fence which are no closed circles as multipolygons always need to be "closed".

See the usage example(s). I have searched for realworld examples. Look at this one.

I am trying to make an example (numbers represent nodes, x-y is a way consisting of node x and y):

1-----2
|     |
6-----3
|     |
5-----4

fence and other tags which apply to the complete area: tag them onto a multipolygon which consists of those outer ways:
- 1-2,2-3,3-4,4-5,5-6,6-1
if I assume there is a car parking in the south: tag the car parking tags to a multipolygon which consists of those outer ways:
6-3,3-4,4-5,5-6

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answered 16 Dec '13, 13:06

aseerel4c26 ♦
32.6k●18●248●554
accept rate: 18%

edited 16 Dec '13, 13:38

Okayokay, seems here are some relation haters. ;-) Note that I do not recommend this method. I just mention that it is possible. Also note that this help site is no policy vote. Please instead just comment what the downsides of this are in your opinion.

(16 Dec '13, 14:11) aseerel4c26 ♦

1

yeah, you can move everything to multipolygon relations, even a simple square. Problem is readability and maintainability. Once the same way (or segment) belongs to more than one relation, interpreting the data becomes harder for humans. You move to a more abstractive world where only few people feel confortable.

(16 Dec '13, 14:53) Pieren

@Pieren: Thank you. Yes, it has many downsides. But using overlapping ways also has downsides. I still think that my answer is helpful to the original question, which is about multipolys.

(16 Dec '13, 15:11) aseerel4c26 ♦

you can create a multipolygon and won't have any problems or overlapping ways. You simply add the fence-tag to the fence-pieces and leave the non-fence parts of the perimeter untagged (but you add them as outer parts to the multipolygon relation).

(18 Dec '13, 12:50) dieterdreist

Multipolygon of fence, building, fence, building, car parking

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