[Tagging] Additional detail of Levee mapping via embankments
johnw at mac.com
Mon Nov 11 06:25:13 UTC 2019
> On Nov 11, 2019, at 12:52 PM, Joseph Eisenberg <joseph.eisenberg at gmail.com> wrote:
> We use two tags for rivers: `waterway=riverbank` (or natural=water +
> water=river) for the area and waterway=river for the central line of
> the river.
Thanks so much for all of the clear and thoughtful replies.
I sometimes mess up tagging schemes or tag names during discussions, and it leads to confusion, but this was a total misunderstanding of embankments.
It seems I was (very) confused, possibly by misreading it several different times. I have mapped 40km of levees wrong, with an improper lower bounds line. I’ll have to fix it.
I now understand that my embankment lines at the top are the (only) proper way to map the edge of the embankment.
I am interested in mapping the extent of the levee/embankments with some kind of outer/lower line, either as a single area or as 2 related ways for a levee.
it is interesting to me that a levee is a way that marks the “centerline", while the embankment maps the top edge of the slope - yet there is no documented way to map the *area* of the levees nor embankments. my “lower” embankment line (which is apparently very bad mapping) makes the extent of the embankments that make up a levee. while they sound simple, our levees are *covered with* parallel and intersecting roads. some levees will have 5 parallel ways on them for different kinds of traffic. similar to man_made=bridge, showing the area used by a bridge is very useful.
to me, both man_made=embankment and man_made=dyke need a way to express the area they take up, because mapping via a width value varies too much to be mappable, especially when they are in very complicated shapes - and very easily mapped via imagery.
to me, these levees are not only a major feature worth mapping, but considerably helpful to understand the mapping in an area. They are very large artificial barriers which greatly restrict access, as well as one of the few safe places during a typhoon.
I will think about how area:man_made=embankment & area:man_made:levee would be useful compliments to the existing tagging without requiring any changes to the existing tags.
There is a big discussion on the tag discussion page ( https://wiki.openstreetmap.org/wiki/Talk:Tag:man_made%3Dembankment ) about mapping embankments by area using the existing man_made=embankment on a closed way (only generating an area when paired with area=yes), but in that case there is no way to tell which side of the area is the “top” of the embankment, which is the intended data the line is meant to represent.
Your comments have been extremely useful/helpful, thanks.
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