Major road minzoom #221

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1. nvkelso commented on Feb 27, 2024

   

   nvkelso

   on Feb 27, 2024

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   A few solutions (there are probably more):

   • Brute force: Show non-motorway roads earlier, at expense of clutter in more developed countries and large file size increases in same tile areas.
   • Algo: Calculate directions between major cities shown at the next zoom (or zoom +2) using that "next" zoom's place nodes and OSM road network and show the deduplicated way results (to reduce tile size) at the current zoom, regardless of the highway class, while preserving the highway tag so motorways versus non-motorway could optionally be styled distinctly. This should ideally be done per data release but in practice happens one-off and then can go stale with bit rot and operational decay.
   • Curation: Switch to Natural Earth for low zoom roads from OSM. While this would provide coverage and not be too big a tile size incrase, downside is the roads there in NE v5 are out of date and don't match up geometry wise on zoom in to OSM zooms. However, NE v6 is around 50% done redrawing the roads to solve that problem. Overtime the curation would need to be updated.
2. wipfli commented on Feb 27, 2024

   

   wipfli

   on Feb 27, 2024

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   What about a per-country minzoom? For example in Switzerland I am happy with trunk at z6, but in Tanzania I would prefer trunk already at z3. This of course leads to some questions about styling...
3. nvkelso commented on Feb 27, 2024

   

   nvkelso

   on Feb 27, 2024

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   What about a per-country minzoom? For example in Switzerland I am happy with trunk at z6, but in Tanzania I would prefer trunk already at z3. This of course leads to some questions about styling...

   That can work well for clusters of countries that all have the same network pattern (eg trunk versus motorway more common as highest functional class in the country). It works less well if a more developed country is next to a less developed country and the roads might appear to start/stop at country boundaries because different threshold were used. In Europe this could be observed between Germany and Poland and Poland and Ukraine. In Africa this might add extra road detail in say Egypt and South Africa but overall improve the whole continent (a collection of countries with a localized config enabled).

   It could be a good interim approach, but is blocked here in Protomaps basemap repo by #44. Now that the NL.net grant is active this may be a priority @bdon?
4. nvkelso

   added

   enhancementNew feature or requestNew feature or request

   on Feb 27, 2024
5. bdon

   added a commit that references this issue on Feb 24, 2025

   Road relations (#386)

   ...

   a974fe9
6. wipfli commented on Mar 11, 2025

   

   wipfli

   on Mar 11, 2025

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   Can be implemented with roads matching rules #407
7. pekkine commented on Oct 5, 2026

   

   pekkine

   on Oct 5, 2026

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   The US rules in highwayZoomsIndex already do per-country minzoom, so I added Finland the same way.

   Finland tags its national road network highway=trunk, not motorway, so z3 to z5 carry almost none of it. All of Finland fits on a phone screen at about z3, which is where we need it for a public weather service.

   PR: #640