(I mis-sent this email)
> On Nov 13, 2019, at 3:44 AM, Richard <ricoz....@gmail.com> wrote:
>
> We need new tags for the bottom of embankmets, top of cuttings, bottom of
> cliffs, earth_banks
> and maybe a few others if we want to map them.
that is very true.
I think we can cleanly do this with the ways you mentioned.
We need to chose a scheme for these “base” tags that doesn’t reinvent the
wheel, isn’t vague, and can easily be interpreted. my mis-reading of embankment
led to some big problems, simply because I assumed the tag could document
things it couldn’t. Your tags look really good to me.
> On Nov 11, 2019, at 6:15 PM, Martin Koppenhoefer <dieterdre...@gmail.com>
> wrote:
> A relation seems easier to evaluate and explicit, while a spatial query
> heuristic will inevitably fail in some cases
I think there is a need for a basic relation, if I understand Martin correctly,
to simply associate the two lines, (for example, an =embankment and an
=embankment_base pair). When mapped, they are not joined. They are merely
adjacent. I am not sure of what “type” of relation to choose in iD, but I
assume someone will tell us which type to use.
When mapping a simple cutting or embankment, you would have only one “base”
line adjacent - so there is little ambiguity, and the relationship can be
inferred (IIUC), but in complicated tagging, there could easily be a situation
where which base belongs to which line is unclear, and lead to problems.
Simply putting them into a relation says “these members are related” and the
renderer can know for certain that these two ways that don’t share nodes are a
pair, no inference needed.
This again raises the question of levees - is the levee worthy of it’s own
levee relation? do you put all 4 embankment lines into relation with the
man_made=dyke line? this seems to be the only solution to:
- properly group the embankments with the levee
- not have to use super=relations (putting the embankment relations into a
levee relation)
- providing the most flexibility to weird situations
- allowing for the extent of the top of the levee to be defined (large levees
have varying width tops with usable areas, as shown, in which a “way” is
insufficient ).
But I am unsure that this is the “only way” and perhaps putting the two
embankment relations + dyke line into a levee super-relation would allow
mapping of the embankments to be a uniform process (making mapping the details
of levees a bit more complicated at the expense of standardized embankment
mapping).
Javbw
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