Road surface

[adamfranco]

This PR suggests an option for distinguishing road surface by overlaying a lighter version of the fill color over roads when they have OMT surface=unpaved.

Dashed fill was chosen because this is a common way of indicating surface in various American print maps and doesn't overly distract from the other meanings of the road symbology.

Still to do:

• Validate unpaved bridge rendering. The style doesn't seem to render bridge wings, but this PR doesn't seem to break anything
• Validate tunnel rendering. The style doesn't support primary-tertiary tunnels yet...
• Find motorway/_link example and validate unpaved rendering.
• Fix z<12 rendering if possible.

Example renderings:

Motorway:
I haven't yet found an example of an unpaved motorway, but I'd imagine that cases could exist, such as motorways where construction is underway for a long time and paving hasn't yet completed.

Brazil: unpaved motorway_link:
http://localhost:1776/#16.83/-21.316703/-48.374253
https://www.openstreetmap.org/way/492811562#map=17/-21.31731/-48.37384

Tanzania: unpaved trunk and primary:
http://localhost:1776/#12.53/-5.11778/31.03149
https://www.openstreetmap.org/#map=13/-5.1178/31.0315

Note that this dashed overlay isn't working at z=11 and lower. I'm not sure why... OMT or something I'm doing wrong?

Peru: unpaved primary road:
http://localhost:1776/#13.07/-9.85917/-76.1688
https://www.openstreetmap.org/#map=14/-9.8592/-76.1688

Maine: unpaved secondary road:
http://localhost:1776/#12.99/45.68226/-69.7658
https://www.openstreetmap.org/#map=15/45.6812/-69.7739

Zooming in -- note that the lighter dashes work on both the solid version and the white-with-casing version.

Vermont: unpaved tertiary road:
http://localhost:1776/#14.38/44.09141/-72.94351
https://www.openstreetmap.org/#map=15/44.0896/-72.9384

[ZeLonewolf]

Based on:
https://github.com/openmaptiles/openmaptiles/blob/7d08e5b97e560efd783282d0e09fae4041fb84d7/layers/transportation/transportation.sql#L333

Surface information is suppressed in OpenMapTiles starting at zoom 11.

[adamfranco]

Here's an example of an unpaved secondary tunnel in Peru: https://www.openstreetmap.org/way/298172122#map=19/-11.85747/-75.74448

If this rendering conflicts with tunnel rendering, these cases are probably few and far enough between to ignore.

[adamfranco]

I've validated that motorway_links are now working successfully.

@ZeLonewolf should this wait until tunnels are implemented in the road_layer branch to confirm before merging? Otherwise I think it is operational and ready for more review.

[ZeLonewolf]

This looks good to me. The only question is how we might style railroads so they don't conflict. I was thinking that rail could be done in a simple line style like this:

Or perhaps a double-line style.

[ZeLonewolf]

Looks good to me!