Small dams are too visually prominent at z13

[Adamant36]

As of right now all dams are rendered at the same beginning zoom level. While it works for larger cement dams attached to large bodies of water, it looks weird and cluttered for smaller earthen dams that are connected to ponds. Especially if a bunch of them are mapped in the same area. Currently waterway=dam has 1,829 instances where it also has the material tag. My suggestion is to keep cement dams rendered at the current level, but start the rendering of ones tagged with material=dirt at either z14 or z15. Z15 would be best IMO, but either would be an improvement. Aside from looking better, it would also encourage people to use the material tag more.

[jeisenbe]

Do you have a link to the area in the example rendering?

[Adamant36]

https://www.openstreetmap.org/#map=13/40.1236/-122.4254

[imagico]

Rendering of dams is something that can definitely be improved on - though this is tricky due to technical constraints and the lack of established mapping practice for additional details on them.

The suggestion you made however is not going to work i think:

• material is tagged on dams only in about 1 percent of cases and dirt is definitely not a sensible value.
• the inner structure of earth/rock fill dams is not practically verifiable and hence surface tagging is almost as common as material tagging. Interpreting material would essentially incentivize adding guessed values or tagging for the renderer.
• If at all there is a relationship between size of dams and material it is that the largest dams are usually earth/rock fill dams (which is the opposite of what you seem to assume).

I would not mind in principle deciding rendering of dams based on intersecting waterways or way_area of intersecting reservoir water polygon so if you want to re-purpose this issue for that would be fine with me. This would however require a join query which adds complexity and possible performance issues - which would need to be weighed carefully against the benefits. Tuning the styling might be a better option.

Otherwise i would suggest to close this - using material for starting zoom level selection definitely does not work for me.

[jeisenbe]

Perhaps part of the visual issue here is the strong line weight and dark color currently used for dams mapped as linear ways?

The @dam-line color is #444444 Compare to @dam #adadad (used for the fill color for dams mapped as areas) @weir-line #aaa expands as #aaaaaa (And this is rendered as a series of 2x2 pixel dots rather than a solid line)

There is barely any difference between #adadad and #aaaaaa, so why not switch @dam and @dam-line to use #aaa like weirs and lock gates?

[jeisenbe]

I’ve changed to title to "Small dams are too visually prominent at z13” to better explain the cartographic problem, and so we can continue to discuss different possible solutions in this issue.

[jeisenbe]

If we did want to distinguish concrete and other solid materials from earth/rock fill dams, we could use a thinner, less heavy outline for those mapped as areas, but as mentioned above, less than 1% of dams currently are tagged with this information so it is not yet a rendering priority.