Navigating the Maze – part 1
This post is part of a longer series on map design questions. I have not written much more recently on my work on the alternative-colors style and there is a bit of a backlog of topics that deserve some discussion. I will make a start here with the most heavy of all – the roads. In this first part i am going to explain the OSM-Carto road rendering system and analyze its issues and limitations.
The without doubt most complicated part and for any OSM-Carto map style developer the most serious challange when working on OSM-Carto or one of its derivatives is the roads layers. As Paul some time ago compactly put it the roads rendering in OSM-Carto alone is more complex than many other map styles are in total. Roads (and in context of OSM-Carto roads by the way generally refers to all lines and other features along which land navigation of humans takes place – including roads for automobile navigation, paths for navigation by foot, animal or other vehicle as well as railways and traditionally also runways and taxiways on airports, which however have more recently been moved outside of the roads layer system in OSM-Carto) can be complex in their semantics, connectivity and above all in their vertical layering. Representing that in a well readable and accurate way in a map is a challenge to put it mildly.
Most simpler map styles take shortcuts in this field – which tends to show up in map in non-trivial situations. See for example the following case example:
