[Tagging] better mapping for embankments / slopes

Volker Schmidt voschix at gmail.com
Tue Nov 29 21:34:21 UTC 2016


On 29 November 2016 at 22:03, Warin <61sundowner at gmail.com> wrote:

> Not all embankment have 2 slopes
>

To my understanding of the English term, an "embankment" is the equivalent
of dyke or levee and is a long, narrow man-made elevation. Therefore they
always have two slopes of opposite directions (leaving out the ends)

What Martin proposes should get a different tag name to distinguish it from
an embankment. The term "on-sided enmbankment" is used in OSM for this, but
I do not like it at all. I strongly recommend to use a different tag name.
I used "slope" as this is the term used to describe the inclined flanks of
levees (=embankments).


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
nodes?

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>
> 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 alternatives?
>>
>> Cheers,
>> Martin
>>
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