[OSM-talk] Overlapping & Crossing ways

[Robin Paulson]

2008/5/30 Mark Williams <mark.666 at blueyonder.co.uk>:
> This is another Potlatch grumble - but it's not really Potlatch, it's the
> internet.
>
> I just found a whole lot (really, a lot) of overlapping ways with some
> really old data (Potlatch alpha & before) buried under new versions from
> Potlatch v0.6a & 0.8 - for instance, the M25 Junction 30 had 3 (three!!)
> layers of roundabout in places. 2 hours has seen most of it off... I wonder
> how much of other peoples' time I just deleted?

i had a similar problem near me recently. i had a lot of streets that
had been 'helpfully' drawn, without tags, in small, unjoined segments.
after i mapped the area in question, i merged all the relevant
segments and tagged them as appropriate (all in potlatch, approx.
version 0.9a i think).

i was looking at the rendering the next day, and realised that when
they'd been merged, a new long road had been created, but the original
short pieces had not been deleted - not at all what i had imagined
would happen, and surely not intentional. i guess this is what
happened here with your m25 problems

maybe we need an extra warning category in maplint, to indicate
duplicate ways  - i.e. using the same nodes and having the same tags?

>
> I can't imagine this was done knowingly; I suspect that the redraw was
> sufficiently slow that it looked unmapped to a less experienced user, and
> allowed time to re-draw the ways before it showed up.
>
> Would it be possible to make it draw ways & nodes BEFORE the aerial
> photography, so this can't happen is less likely? I had assumed that having
> to move from the map to the editor would prevent this, but I think folk are
> scrolling miles & never seeing the rendered version. Maybe a slippy map
> under the photography? Or make it impossible to add any nodes until it's
> completely finished loading?
>
> I also had a good number of "High Road; Low Road" names to untangle, and a
> river to unplait.  I do hope it stays done this time :)