On Wed, 29 May 2019 at 13:42, Christoph Hormann <[email protected]> wrote:
> > man_made=embankment is almost exclusively used for one-sided artificial > slopes - prominently supported by OSM-Carto rendering it this way. > That surprises me. Not that either man_made or barrier was used for one-sided artificial slopes but that a one-sided slope is considered an embankment. It's not even clear to me that something counts as an embankment if it is not higher than the ground on both sides. Not necessarily the same height difference on both sides, but a difference nonetheless. Otherwise it's just a slope. barrier=embankment is in the relatively small volume of use mostly used > for symmetric structures with slopes on both sides. > That may be more an artifact of which tags are used by editor presets for embankments. I believe iD changed from barrier to man_made fairly recently. The thing is that railway embankments are man-made and their purpose is not to act as barriers. But fortifications, whilst also being man-made, are specifically intended to be barriers. I'm not entirely convinced we should be deprecating either tag, but man_made is more generic so if we must restrict ourselves to one tag then that is the one. I think we throw away some detail if we restrict ourselves to man_made, but we would be deceptive if we tagged railway embankments as barriers. > And current tagging documentation does not provide a clear suggestion > how to tag such - if with embankment=yes as a standalone tag or with > man_made=embankment + embankment=both or embankment=two_sided. > For me this is somewhat similar to the difference between a wall and a retaining wall. Retaining walls, by their function, have a significant height difference between the two sides. Economics may mean the height difference on one side is so small as to be negligible. Ordinary walls have no such difference (or perhaps no more than a centimetre or two). To my mind, embankments are two-sided just as non-retaining walls are. Consider a "one-sided embankment." What would things look like if the embankment had not been constructed? The drop from high to low shifts position a metre or two. A different angle of slope, maybe. Without knowledge that there was an artificial construct present, you'd have no way of distinguishing the two situations just from simple observation. A retaining wall is distinguishable because of man-made materials, but a "one-sided embankment" is not. -- Paul
_______________________________________________ Tagging mailing list [email protected] https://lists.openstreetmap.org/listinfo/tagging
