vknoppkewetzel
commented
4 months ago I personally do not think we should implement a 4 color country fill at low zooms (or low-zoom) in the current "main" style, although I can see that being useful as a separate style
The case to not do it
I do not think the 4 color theorem would specifically help a user identify different countries at low zooms - if that is the goal, I think there are other ways to support a user identifying and differenting countries at low-zooms.
At low zooms (on an unknown screen size (map extent available), with dynamic styling rather than highly customized styling*), I have trouble seeing how the 4 color theorem would be more helpful than country borders
In the "super low" zoom above, I see country borders and can differentiate them. I mostly at this low zoom can't differentiate some countries in terms of "what they are"since not all labels show up (a product of standard dynamic zoom level styling to help with legibility and not having too many things stack, as we know of course).
zoom in to z5, still low zoom:
In an interactive map, we always have the labeling coming in and out as some countries are biggers than others as noted above, but I still see country boundaries differentiating here.
I think if it is a priority to differentaite even further for a user to immediately identify countries at low zooms we can:
- increase boundary contrast/color rather than the 4 color theorum.
- consider not showing any "State lines' until farther in, if it seems a priority to only highlight country areas at low zooms to help avoid confusion/differentiation. We could do either or both to support country legibility.
- make country names smaller to make more of them show up (this is a pending update - update vs current!)
- have a far more custom styling of labels and not rely on dynamic styling but be very intentionally at specific zoom levels (not sure I recommend over history haha... dynamic styling is our friend with history constantly changing!)
IMO, doing a 4 color country coloration wouldn't remove the issue of people knowing what country specifically is at lower zooms, largely due to the fact that color or existing boundary will show polygons, but they still won't see all the labels at once at low zooms.
If we do it
If we do a four color map to differentiate country polygons, I agree, finding the right colors matters, but I also think only doing them at low zooms wouldn't make sense for a user. If I want to differentiate countries at z5 and am "used to" doing so as a means to determine different countries...:
... I will also want it at z9/mid level zooms where I still see country borders. And design-wise, it is better to have the cognitive reinforcement of an aid across zoom levels. I think it would be okay to fade out at high zooms. z9/mid level zoom:
It would be disorienting if it is an aid, to stop it after low zooms and not have it in mid-zooms.
In order to ensure users don't feel disoriented / don't use a visual cognitive aid at mid-level zooms, it would mean doing a bit of redesign across the map , across many data layers that would be affected.
If that seems like the path forward, I think that can be done, we just would be moving away from this main design.
Alternatively, this could be an intentional separate style that is more "reference map focused", maybe a good use of a "political map style" maybe? Then we don't need to be considering all-the-data like in main, but rather, just relevant poltiical info - boundaries, place labels, plus major natural features (ex: mountains/bigger rivers) ex:
1ec5
Bauer33333
jeffreyameyer
In OSM World Discord, a mapper suggested shading each administrative area in a different color from its neighbors, as one typically finds on a political map or general-purpose map that isn’t heavily transportation-centric. A choropleth would be useful because the user won’t necessarily be familiar enough with the historic boundaries in a given area to orient themselves like they would using present-day boundaries.
The good news is that the vector tiles already represent boundaries as polygons. The bad news is that the polygons contribute to performance issues and probably need to be eliminated at some zoom levels: #701. But at high zoom levels where we only show countries, we can probably still get away with simplified boundary polygons.
The bad news is that we’ll have to determine the color that each country should be filled with. For a map that depicts a single point in time, the four color theorem guarantees that no two adjacent areas share the same color. We probably have access to tools to calculate the four-color-theorem colors when generating the tiles. However, our tiles use a single feature to represent a boundary over time. Even if a boundary doesn’t change, its neighbors can change. I’m not sure that the four color theorem is proven for the more general case.