[OSM-dev] Planet file with preprocessed lines/polygons

Christoph Hormann 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.

Christoph Hormann

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