|Tagging:||network=international, national, regional, urban, local|
|Applies to:||relation, way, node|
|Definition:||To tell the importance of level|
|Rendered as:||Renderer can guess zoom level|
Renderers can't display on a map in each zoom level, so they have to make a selection. The more important an object is, the earlier (in zooming in) the object should be rendered. For highway=* as an example you see motorways starting in zoom level 3 and residential roads starting in zoom level 12 and much smaller.
I want to propose something like this too for other objects, because the big cathedral in the city might be more important to be displayed on a map than the small mountain church. This proposal is inspired by the network key (for cycleways: ncn=national cycle network, rcn=regional cycle network, ....).
For renderers this tag is important, to decide from which zoom level on an item is being rendered, for example see the OpenCycleMap, where more and more cycle ways are rendered as you zoom in. For roads the value of highway can be used, motorways on high zoom levels, then primary, secondary and tertiary roads and finally the minor roads like residential and unclassified. But a system like this is missing for railways (there's only railway=rail) and it could apply to other objects to (cathedral, church, chapel which all is just amenity=place_of_worship).
I propose to call this key "importance" with a value which refers to the area this object is important for, e.g. regional or urban. We could later rethink the values for network=*, because there's a redundancy with "ncn", "rcn", "lcn" (a name of the network of the region might be more appropriate and is already used like this for routes of public transportation, not to be confused with operator=*).
Proposal and Examples
Why don't we introduce this value:
- importance=international: Routes and other items of international level
- Rail routes connecting the capitals, e.g. Paris - Munich - Vienna - Budapest
- Main ways for railways, because at the moment there's no possibility to guess the importance (unlike highways where you have motorway, trunk, primary, ....)
- for or the most important rivers (e.g. Danube, Rhine)
- Eurovelo cycle ways
- importance=national: Routes and other items of national level
- Rail routes crossing countries and connecting the cities, e.g. Munich - Nuremberg - Berlin
- Cycle routes crossing countries
- (Railway, Bus, ...) Stations for interchange between national and lower level transportation
- Buildings: cathedral, parliament, ...
- importance=regional: Routes and other items important for the region
- S-Bahn routes
- Stations where you can interchange trains and change to regional and local buses
- railways: branch lines (Nebenbahnen)
- Building: bigger hospital, state agency
- importance=urban: Routes and other items connecting the districts of a city
- Tram and Bus routes
- Stations for interchange between public transport routes
- Bigger Shops / Shopping Centres
- Recreational parks where the people of the city meet, Central Squares
- bigger church, castle
- Stations of Public Transportation
- Short bus or collected taxi routes
- railways through parks, museums railways
- small church, supermarket, market, pub
- importance=local: Routes and other items important for the city districts
- small chapel, small shops, park bench, rubbish bins