[Talk-GB] non-squared buildings

SK53 sk53.osm at gmail.com
Mon Sep 30 10:47:43 UTC 2019


I'm sure that in one of the SotM talks someone mentioned that there are no
right-angled buildings in New York City (or at least downtown Manhattan).
I'll see if I can find the relevant talk.

The general issue is really one of poorly mapped buildings, for which
non-squaring is just a proxy measure. Pierre Beland's talk on the first day
was about finding such areas (especially wrt HOT mapping).

Some years ago whilst helping Ralph (another person I didn't get to talk to
at SotM, Hi1) do validation at one of the London Missing Maps events I
noticed a quirky thing. If you square a building in JOSM and then resquare
it in iD or Potlatch the nodes move slightly. Apparently the reason is that
JOSM squares based on a geoid whilst the other two editors just work on the
principle that the editor viewpoint is small enough that one can use
'naive' geometry operations. I imagine for accurately surveyed & designed
buildings JOSM's algorithm is likely to introduce additional errors because
the architects/engineers will have used British Grid.

Jerry

On Mon, 30 Sep 2019 at 11:17, Jez Nicholson <jez.nicholson at gmail.com> wrote:

> Some people seem quite animated about non-squared buildings in OSM....can
> anyone tell me why it matters so much? because 'accuracy'?
>
> - Jez
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