[Tagging] better mapping for embankments / slopes
61sundowner at gmail.com
Tue Nov 29 21:03:57 UTC 2016
Not all embankment have 2 slopes .. nor does a 'slope' describe all of
the properties of an embankment. The same problem exists for a 'cliff'
and a 'cutting' ... and stairs that cover a large area. So use what has
been done for them as a guide.
What are the key properties of these features ...
Length - simple set as the length of the way. Cliffs are tagged as a
single way at the top of the cliff, with the right hand side being
'downwards' when facing the direction of the way.
Vertical rise - could be tagged with the height key.. this can vary over
the length of the feature (I have found this on some maps as a number in
meters ... assumed to be the maximum vertical locally rise in meters) To
accomodate teh change in vertical height .. put the height on individual
Slope - or in OSM terms 'incline'. This in OSM is entered as a way along
the top where the slope would be minimal and not what 'we' want to
describe. ... as cliffs, cuttings and embankments are best described
this way I think incline may not be the best thing to tag? Humm stairs
are described using the incline key ... but on a way that goes up ..
leaving the top and bottom free of this. So maybe a top and bottom way
.. with a simple way from bottom to top containing the incline information?
While the 'top' and 'bottom' of natural features can be a bit fuzzy they
are features that should be mapped. Definition? Something for a
geologist? Along the lines of the line formed by the intersection of the
average slope of land before the change to the average slope of land
after the change ( the change being the cliff, embankment or cutting)?
On 30-Nov-16 01:25 AM, Volker Schmidt wrote:
> If you want to micromap slopes you should create a new key "slope" or
> something similar. An embankment has two slopes. It is equivalent to
> dyke or levee. The one-side embankments that are defined in the OSM
> wiki, are in reality slopes and should be retagged accordingly.
> Independently of the name used fo the tag I see the prblem of defining
> where the slope starts, normally these are rounded features.
> On 29 November 2016 at 13:48, Martin Koppenhoefer
> <dieterdreist at gmail.com <mailto:dieterdreist at gmail.com>> wrote:
> Currently we are mapping only one side of the embankment (I think
> it's the upper side, but am not sure if the wiki says this
> explicitly), with the direction. What we would IMHO need is a way
> to map the lower side as well and to combine both. A closed
> polygon will not work I believe.
> The obvious solution that comes to mind is a new relation type: in
> case the upper end is mapped, draw a new way for the lower end and
> combine both with a relation (possibly assigning roles like upper
> and lower, maybe also draw lateral ways (ways that connect the
> ends of the upper and lower ways and defines their shape) in cases
> they are not straight). (The type=area relation does this)
> Maybe it could also be done without the relation, simply by
> tagging the upper and lower ways accordingly, and connect them at
> least at one of their ends with an explicit lateral way (and
> respective tags). This would require from the data user to
> topologically search for the embankment area in order to be able
> to render it (or make other use).
> What do you think, which representation is better? Are there
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