[Tagging] RFC - Feature Proposal - area of steps for pedestrians.

[Tobias Knerr]

On 03.05.19 19:00, Christoph Hormann wrote:
> That illustration does not show the original data so it does not tell 
> very much.

Here's the raw data if you'd like to examine it:
http://tobias-knerr.de/upload/Step%20Polygon%203D%20Examples/
Please excuse the sloppy mapping, those are just intended as tests.

> Like for example classic curved stairs:
> https://www.alamy.com/stock-photo-one-of-the-curved-stone-staircases-at-picton-castle-near-haverfordwest-58935307.html

Indeed. Winding/curved steps are a separate category from the straight
steps this algorithm is designed to solve. As I said previously:

On 11.04.19 23:28, Tobias Knerr wrote:
> Note that the method I describe above does not even try to work for
> winding steps (i.e. those which you don't ascend in a straight line).
> But there are other algorithms that would work for those, and the two
> classes of steps could potentially be distinguished with a tag.

While you correctly point out several further limitations, I think it's
important to keep in mind that this isn't an attempt to define a data
model that works for everything. It's about finding a sweet spot that
works for a sufficiently large class of steps to be worth it and is
still relatively simple.

As for that data model that works for (almost) everything, I believe
that will have to be drawing a way across the edge of each step.
Increasingly complex staircases could then be modelled accurately by
simply adding more information (if the mapper is in the mood for
micromapping):

1. Just draw a way.
2. Additionally draw a polygon around the steps.
3. Additionally draw a way along the edge of each step.

Each level of detail would just add more data on top of what's already
there, which I believe is a desirable property.

Tobias