2015-03-05 10:20 GMT+01:00 Tobias Knerr <[email protected]>: > My impression from previous discussions of the topic was that the steps' > shape within the area is hard to define. >
usually you will be able to connect the first (and further any n-) node of the upper and lower ways and divide them by (step_count-1) (if given). These are the intermediate projections of the risers (i.e. what you typically draw as lines in a technical drawing). Now for the scales we use in OSM typically, this would very likely result in too narrow line distances for common zoomlevels, so you'd probably omit half or two-thirds (or even more) of the lines for rendering. This all depends of course how big the single steps are. For reference, typical steps are 27-30 cm large, outside 30 is quite normal, because they tend to be around 15-16 cm high (and this determines the ideal largeness). > You propose the restriction > that the upper and lower boundary need to have the same number of nodes. > I had proposed this because it would make rendering easiest. It is not strictly necessary though, you could also compute more complicated algorithms that use e.g. intermediate nodes in the ways according to the distance to the starting node. It doesn't matter for straight steps, but will matter for curved ones or ones that have angles. If the amount of nodes is equal it will be most probably the best idea to use these existing nodes for the interpolation of the steps. My proposal (this one here is basically an excerpt) didn't require equal node amounts, it just encouraged the users to do it like this. Regarding the steepness of the steps and how to map them, I'd not only suggest to use "incline" with a percentage (like it is currently done in the area steps proposal) but also permit to enter the height and largeness (sorry for my English, this is intended as the projected distance of two consecutive risers) of a single step (projection of riser) because these tend to be the same along the whole steps (otherwise people risk falling), and they are easier to survey (no need to calculate). For who reads German, here is an interesting article in wikipedia about this aspect of steps: http://de.wikipedia.org/wiki/Treppensteigung Cheers, Martin
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