Differentiate natural=tree rendering by leaf_type/leaf_cycle

[imagico]

We currently render natural=tree with a non-blocking static circle symbol independent of secondary tags (last modified in #4448).

leaf_type/leaf_cycle are tagged on 3.5M/2.1M trees - making this one of the most widely tagged secondary classifications in the database we do not render. See https://taginfo.openstreetmap.org/tags/natural=tree#combinations. Knowing the type of trees in an area can be helpful for map users (for example to assess the shading trees provide, falling leaves of deciduous trees). Even beyond concrete practical use cases, the value of trees, in particular in urban environments where most of them are mapped, is increasingly appreciated by many world wide, mappers' efforts in differentiated mapping of them are testimony to that, and a better differentiation in rendering would help supporting that.

We should consider that at z19, maybe also at z18, the symbol size we use would allow a differentiation. It is still difficult to make this work because the way we currently render overlapping trees depends on the uniform fill rendering of the current design. But options to solve that exist.

See also #4256, #4448, #4690.

[tjur0]

For leaf type I would use a circular pattern around the stem for broadleaved and use a linear pattern radiating out from the centre of the stem to the end for needleleaved.

That symbolises the pointy nature of needle leaves and the round nature of broadleaved leaves.

For the leaf cycle I would add an outline on the edge of the leaves if the leaf cycle is evergreen to indicate they are “stronger”.

Also, I think the trees with leaf type or leaf cycle should be slightly bigger overall and significantly bigger at high zoom. That would give more room for the patterns. And would be the only indicator for leaf cycle deciduous trees.

Ideally for the leaf cycle we would simulate the seasons by making the leaves red in the autumn and remove them in the winter etc. But this is not practical on a pre-rendered map.

[imagico]

The difficulty is how to handle overlapping trees.

Ideally for the leaf cycle we would simulate the seasons by making the leaves red in the autumn and remove them in the winter etc.

That would require federating the style because seasons obviously differ between northern and southern hemisphere. So this is out of the question.