Allow tracktype=grade2 together with surface=ground

[Nekzuris]

I don't think surface=ground is incompatible with tracktype=grade2.

According to the wiki, ​grade2 is mostly solid and without grass in the middle.
The appropriate surface is often ​compacted but that is always a bit subjective, I use it when material has been added and worked on by machine, but sometimes the road is simply the natural ground that has been naturally compacted over time with regular use.
For that I use surface=ground because it's not dirt and I think it's more precise than unpaved, it's also not grade3 because there is no grass in the middle.

​https://github.com/osm-fr/osmose-backend/issues/2427

This warning comes from here:
https://josm.openstreetmap.de/browser/josm/trunk/resources/data/validator/combinations.mapcss#L348
And I would also remove ice and salt.

[stoecker]

Comes from #22102.

[stoecker]

Reviewing the tags I agree that ground, ice and salt may be supported for type 2 even if uncommon.

So I don't think we should warn in these cases.

[stoecker]

Other Comments?

[GerdP]

My understanding is that type 2 means something like "not paved" and "no soft material". surface=ground can be anything from very soft to hard like stone.

[stoecker]

So surface=ground + tracktype=grade2 would specify ground, but not soft. And thus it is a valid combination I think, or?

[GerdP]

Yes, I agree. Not so sure about ice and salt. My understanding is that both can be soft in rainy conditions.

[stoecker]

I assume they are valid in regions like poles (ice) and deserts (salt).

[Nekzuris]

Good that we agree on ground + grade2.
I'm not sure about salt, but I don't know how you can have soft ice. But most ice roads are seasonal and tagged based on the material underneath, often gravel or compacted.