Add a water layer

[dschep]

With the layers currently available, you could almost make a map, except that you wouldn't have any water bodies!

[jake-low]

Definitely open to adding a water layer. Some questions for you (and anyone else who's interested in such a layer):

• Should it contain water areas only, or also waterway lines? How about water-related POIs like locks, dams, waterfalls, boat launches, etc?
• What columns should be included?
• What are the use cases for this layer? Cartography is one you already mentioned, but Layercake's main purpose is to allow you to easily export specific types of OSM data for analysis (e.g. hydrography), or to use in applications like search or geocoding. Identifying the use cases for water features would probably help us decide which features and tags to include.

[dschep]

• I would expect areas and lines. Hadn't though of the others
• name, "type", intermittent.. 🤔
• I didn't realize what the main purpose was. That def would be reason to include waterway lines!

[jake-low]

To clarify, I think both water areas and waterway lines should be available through Layercake; the question is whether they should live together in a single water layer or separately (in say waterbodies and waterways layers). And which additional feature types should be included in those files.

The current highways layer includes everything in OpenStreetMap with a highway=* tag. This includes roadways but also point features like turning circles, streetlamps, and trailheads, and area features like rest stops. This seems to work pretty well, and gives data consumers more flexibility than it would if we applied some filter criteria at build time (they can filter themselves however they want when downloading the data). So similarly, I could see an argument for a waterways layer to include everything tagged waterway=* which includes water flowlines but also waterfalls, dams, locks, etc.

For water areas, which are tagged differently in OSM (natural=water), the question is whether they should have their own layer or whether they should be included in the same layer as waterways.

Also, I presume that most data consumers who want lakes also want oceans, which are modeled implicitly in OSM (by enclosing them in natural=coastline ways). Layercake would need to reassemble these into polygons using e.g. https://osmcode.org/osmcoastline/ and then emit the ocean as a polygon (or more likely, slice it up into a grid, since a single enormous polygon would be painful to work with).