Same rendering for barrier=ditch and walls

[jeisenbe]

Expected behavior

• The tag barrier=ditch is used to tag dry linear depressions which are normally not filled with water, except perhaps during flooding, and instead serve as a barrier to travel
• Such ditches are barriers to most motor vehicles, but are usually only a minor inconvenience to pedestrians, equestrians and bicyclists, similar to an intermittent waterway=ditch or waterway=stream. They may also be passible for off-road vehicles.
• Therefore, it is reasonable to expect that barrier=ditch will be rendered differently than barrier=wall and barrier=fence, which are significant vertical barriers, normally not passable to pedestrians, equestrians or cyclists.
• There should be some subtle similarity between waterway=ditch + intermittent=yes and barrier=ditch - because ditch barriers will often have running water at least during heavy rains or floods.

Tag:barrier=ditch

Actual behavior

• The tag barrier=ditch renders identically to vertical barriers including barrier=wall and barrier=fence and barrier=retaining_wall
• There is no similarity between the rendering of waterway=ditch + intermittent=yes and barrier=ditch

Link illustrating the problem

Ditches in Libya (east to west) with fench (around police area) and intermittent stream.
https://www.openstreetmap.org/#map=16/31.9764/10.6907

[imagico]

Note in a related problem the combination of waterways with barrier=ditch is still rendered in a confusing fashion:

https://www.openstreetmap.org/way/447594080

IIRC this was meant to be fixed but was not due to an operator precedence error in SQL code.

I would be against rendering barrier=ditch in a way that implies the presence of water.

[jeisenbe]

I would be against rendering barrier=ditch in a way that implies the presence of water.

Agreed. I was thinking of trying a dark thin line, similar to other barriers, but using the same dash pattern as intermittent ditches - though that dash pattern should probably be improved (longer dashes, shorter gaps). It might also help to add a "halo" on each side, like with ditches.

The combination of waterways with barrier=ditch is still rendered in a confusing fashion:

That's surprising! In the line-barriers layer we have this limitation:

WHERE barrier IN ('chain', 'city_wall', 'embankment', 'ditch', 'fence', 'guard_rail',
                  'handrail', 'hedge', 'kerb', 'retaining_wall', 'wall')
              OR historic = 'citywalls'
              AND (waterway IS NULL OR waterway NOT IN ('river', 'canal', 'stream', 'drain', 'ditch'))

Can we fix it by moving the OR statement to the end like this:

              AND (waterway IS NULL OR waterway NOT IN ('river', 'canal', 'stream', 'drain', 'ditch'))
              OR historic = 'citywalls'

Or is it better to use parentheses?

[jeisenbe]

the combination of waterways with barrier=ditch is still rendered in a confusing fashion:

Can we fix it by moving the OR statement to the end like this:

              AND (waterway IS NULL OR waterway NOT IN ('river', 'canal', 'stream', 'drain', 'ditch'))
              OR historic = 'citywalls'

Or is it better to use parentheses?

[imagico]

Or is it better to use parentheses?

I think it is.

[GunSmoker]

If this would be fixed - then barrier=furrow is probably should be rendered as barrier=ditch (or similar to it)??

barrier=furrow is used to indicate (for example) firebreak furrows - it is not exactly a ditch, as it is just removed top layer of soil. Typically it is also a path.

[Adamant36]

If this would be fixed - then barrier=furrow is probably should be rendered as barrier=ditch (or similar to it)??

The numbers are a little low for it to be rendered at this point. In the meantime it would be cool if there was at least a wiki article for it though. Although, my guess is that it's a redundant tag due to them being extremely similar to ditches. For instance both are used for irrigation. While I know farrows are not as deep as ditches, I'd argue the distinction is superficial and that it's impossible to tell "deepness" from satellite images or even on the ground to a degree. Plus, where would the deepness cutoff for it becoming a ditch be anyway? If there is one, there probably isn't a way to figure it out. At least not by the average (or most) mappers.