[OSM-dev] Planet file with preprocessed lines/polygons
osm at imagico.de
Mon May 15 11:19:00 UTC 2017
On Monday 15 May 2017, Jochen Topf wrote:
> [...] What about non-multipolygon relations like routes
> and turn restrictions? How to represent them? A general format should
> probably allow different options here. But if you want to make this
> is available for download, which variant will it be?
I would like to emphasize this point. We currently have a very limited
set of generally established relation types - essentially only
multipolygons, routes and turn restrictions. The hurdles to introduce
something new here are already high due to the difficulty of getting
application support even though file formats used at the moment do not
yet limit this. If we would have in the future a widely used standard
format for data users that is fixed to multipolygons and routes that
would essentially freeze our open relation type data model into the
currently established subset.
In addition to relations (which are not very popular with many mappers
anyway) there are also cases where geometry information is encoded in
tags for which an universal OSM geometry data format might need to
include support. Practically the best known case is the 3d buildings.
This might not be overly relevant for a purely 2d format. But there
are also possible uses of this concept in 2d. I have not seen this
being used but it would for example be possible to introduce a new
circle geometry based on nodes (like with tags type=circle and
radius=x) that would allow mapping circular features more precisely and
more compact than approximated with a polygon. Of course this would
not be lost in a format allowing freely tagged nodes but at least if
you add indices or would allow such geometries to be part of
multipolygons you would need explicit support for this.
Ok, at the moment this is all fairly theoretical but i none the less
wanted to mention this as a suggestion to keep this in mind when
contemplating ideas on file formats.
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