Wall in water to seperate swimming from water regeneration area: How to map? (Wall, compund lake, regeneration area.)

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1

Ahoj,

I have a question how to map → this correctly:

There is an artificial lake with two areas. One area for swimming, one area with lots of plants for the regeneration of water. Both areas are divided by a wall that is in the water (the water flows in the regeneration area through a dedicated passage and is moved by pump), the top of the wall is at the surface of the water (a few cm above, but slight waves already overflow it).

How to map the wall? Current situation is barrier=wall and height=0. The wall has a considerable height below the water surface. But something like height:underground would not be applicable. Are there tags for in-water detailed mapping? Is height=0 wrong?

Furthermore, how to correctly map the two-partedness of the lake? Current situation is that there are two water bodies mapped which share one edge (this edge is the barrier=wall:

  • The area for swimming is mapped as
    natural=water
water=pond
leisure=swimming_area
description=Badesee
  • The → regeneration basin is mapped as
    natural=water
water=pond
access=no
description=Regenerationsbecken

But they somehow belong together. Is there a way – similar to building:part – to map the whole thing as one body of water and then make sub-features with different properties? Important is that the access=no gets meaning. Or is some type of relation the way to go here?

I know that the regeneation area is heavily overgrown by plants (artificial created and maintained – for the purpose of water cleaning). Should it be mapped different than natural=water, water=pond? natural=wetland, wetland=reedbed for example? Is there some specific tag for this use case?

I mention @MrBean, because this user initially created the feature.

Regards!

2
  1. You can start with location=underwater. height=0 is technically not correct as it is the above-ground height, meaning it should be measured from lowest point on seabed. You can see these are currently ill-defined. Vertical positions in the sea can be measured from the seabed / “ground level”, water level, or different datum. This is complicated by tides and storm surge, and wave set-up (when there are breaking waves). For reference level, depth= is claimed to be using Lowest Astronomical Tide, which is usually the chart datum. ele= is supposed to use EGM96 geoid orthometric height, which is different from WGS84 ellipsoid height in GPS. As this is an independent non-tidal inland water body, I guess using ele:regional= for the national land datum will be easier. There is only seamark:pipeline_submarine:depth_buried= for under-seabed depths, so to speak.
  2. No, you don’t need that. Although leisure=swimming_area or access= (also swimming=no) doesn’t require natural=water or anything else, if they are separated, they are separate. If they have a name they share, type=cluster may be used, although not well-supported now.
  3. You could use water=basin + basin=regeneration first. I’m not familiar with wetlands, but because a regeneration basin is expected to be filled with vegetation for water treatment, the land-cover could be handled separately (or ignored). Compare basin=infiltration, where the bottom surface is permeable.
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Ahoj,

thank you for the advices.

Done. And I won’t map it further right now. This should be enough, unless someone adds the depth of the lake.

On → the wiki page “Key:basin”, I could not find basin=regeneration. Where do you have the information from that it is a valid tag? Or do you suggest that I should just “define” it as valid by using it?

Regards!

4

Oh, I didn’t think much about basin=regeneration. You are free to add it. =pond doesn’t seem to convey this information.

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5

I just did it now that way.

natural=water
water=basin
basin=regeneration