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Some mappers use overlapping objects just to add a trivial tag. For instance there are many overlapping lakes in Skandinavia with the (only) tag "snowmobile" like here There are many similar cases as the image shows, the neighbouring area in the former link (the markers and/or the olive-green over blue areas).
So, my question is - is this practice correct?

asked 14 Dec '17, 21:50

sanser's gravatar image

accept rate: 5%


Please replace the google-shortened links by the full link and upload the image here (there is a image button in the edit toolbox). We do not need to rely on privacy-disrespectful google, do we?

(17 Dec '17, 11:16) aseerel4c26 ♦

Imho the overlapping natural=water is strange, but I don't know if it's better or worse than a simple snowmobile=no without any other tag.

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answered 16 Dec '17, 10:16

yvecai's gravatar image

accept rate: 9%

If there is not any visible sign or border that denotes snowmobiles it should not cover any area. Since the Scandiavian laws are build on Allemannsretten your IMHO to go anywhere with respect.

(17 Dec '17, 14:15) Hendrikklaas

A duplicated natural=water area won't work as expected. Imagine there will be some service for displaying or searching of water areas suitable for snowmobiles. It will then have two contradicting results for this lake.

In my opinion the ways in question needs to be removed and the snowmobile tag has to be added to the "real" natural=water way. I can't imagine some parts of the lake are allowed and some aren't, at least not in such a strange manner as shown in the screenshots.

(17 Dec '17, 15:37) scai ♦

I did not think one second that the snowmobile=no polygon was innacurate, coming from a very bad mapping day, a particularily dry winter, nor a clumsy import :-)

If I'm right and Hendriklaas wrong, then it seems that snowmobile are forbidden only in the area mapped as such. The question is then, do we need to add a tag on the limit from where snowmobile usage is restricted ?

(17 Dec '17, 17:16) yvecai

Thanks for the comments. Yet, I am missing the answer. IMHO adding highly specialized tags (like snowmobile, or piste as is done here, and so on) to overlapping lakes is wrong, even damaging and unfair practice. There are many reasons for saying that. For instance, the OSM wiki says that these tags may be added to tracks and routes (line objects). Much worse, geometry parameters of these speculative areas perfectly mach the parameters of a huge number of wrongly tagged islands as lakes over lakes.
So, map/makers have two options: render lakes over lakes (and miss huge number of islands) or make holes for the overlapping smaller lakes (and creating some virtual islands). Obviously, both options are wrong. Therefore, to help the GIS and map/maker, the local community/mappers should correct this mismatch and avoid the practice.

(19 Dec '17, 14:34) sanser

Probably the natural=water should be removed. You should contact the mapper before to understand his or her intentions.

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answered 20 Dec '17, 00:08

yvecai's gravatar image

accept rate: 9%

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question asked: 14 Dec '17, 21:50

question was seen: 1,850 times

last updated: 20 Dec '17, 00:08

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum