[OSM-talk-be] some thoughts and remarks about border mapping

[Ben Laenen]

On Tuesday 23 September 2008, Luc Van den Troost wrote:
> More and more borders are starting to get mapped. It might be usefull
> to use all (or most) the same guidelines and rules to tag them...
>
> info about boundaries is on
>
> http://wiki.openstreetmap.org/index.php/Key:boundary
>
> some thoughts.
>
> Border FROM or BETWEEN
>
> The border of Antwerpen is not just the border of Antwerpen. It
> always is the border BETWEEN Antwerpen and something else.
> So a border gets left = Antwerpen; right = Borsbeek
>
> ONE AND MORE
>
> One border often are more borders... The Schelde at the harbout is
> the municipality border between Antwerpen and Beveren
>
> At the same time this also is the border between the arrondissement
> Antwerpen and Dendermonde, it is the border between the province of
> Antwerpen and the province of Oost Vlaanderen.
>
> If one includes districts or deelgemeenten it also is the border
> between Berendrecht-Zandvliet-Lillo (bezali) and Doel.
>
> How should it be tagged? I would think it is best to tag it with it's
> lowest admin_level (8 gemeente, or even 9 deelgemeente)
> parts of those borders then could be grouped in a relation for the
> higher levels (if I am right, know NOTHING about relations exept that
> they exist for such things)
>
> Or is it better to tag it at its highest level (like province in this
> case, admin_level 6)
>
> How about the dutch border? It is already there, how does it get
> linked so that one (or computers) know to recognise it as a
> municipality / district / province / ... border too??

The current system doesn't allow for much nowadays. If something is the 
boundary between provinces, and it's also the boundary between 
municipalities, it should be tagged with the admin_level of the 
province. That's the current idea, and it makes province borders bigger 
than municipality borders on the maps.

So that gives you a raster of boundaries. My idea is that these should 
be combined together into relations that have the admin_level of the 
thing its ways enclose. That way you can see that boundary X is a 
province, arrondissement and municipality boundary for example. This 
has never been agreed on, but I think it's somehow applied on the Dutch 
border.

In a truly happy world the boundary ways don't need admin_level and 
should be extracted from its relations.




> BUILD UP AREAS
>
> On some places, like around Leuven, it looks like borders are used to
> mark build up areas (bebouwde kom).
>
> http://www.informationfreeway.org/?lat=50.88048655029894&lon=4.723059
>746415672&zoom=13&layers=B0000F000F
>
> Should we mark 'bebouwde kom' with an administrative border?

No, because it isn't an administrative boundary (there are no 
admin_levels left for it anyway :-) ). I'd do it with relations myself, 
probably others want it with areas. I guess both have their merits.

I also wouldn't tag anything that's representing a built-up area with 
maxspeed=50. Only a tag we agree on which somehow gets translated in 
routers and other applications as maxspeed=50.


> If it is 
> because of a speed limit there are other tags for it (max_speed) and
> if we do, what about zone 30, zone 70, blue parking zone, etc...

I've started some experiments in Berchem (I hereby declare the area 
where I live as my experiment zone :-p).

My idea is that zones should be together. How do we do that? With 
relations of course: the zone 30 where I live: 
http://www.openstreetmap.org/browse/relation/32526 or another one: 
http://www.openstreetmap.org/browse/relation/32838

Note that this makes sense. In Antwerp (and probably other places) each 
zone 30 has a reference number and a name (see the note:* tags in that 
relation). They're also decided on in the city counsel in separate 
decrees (not as part of the decrees about the regulations of each 
street).

And there are a lot more zones of course. Like the public market zones 
like for example: http://www.openstreetmap.org/browse/relation/32719 
which are also decided on in their separate decrees and have their own 
names.

Of course this is my own syntax right now but I think it makes sense 
like that. The market zones can't be done without relations for 
example.

I'm in the process of looking up a lot of decrees about traffic 
regulations for Berchem at the moment (which takes a looooong time) and 
make it all a bit more manageable for myself. This would in the end 
allow easy mapping of (each of these are in their own decrees):
* regulations of streets themselves (mainly parking rules, cycleways, 
oneway)
* zone 30's
* public market zones
* parking zones
* (I hope to find these one day:) school zone 30's
* who knows what else I find :-) maybe the built-up areas from above as 
well.

Of course, all these relations have its drawbacks: Potlatch especially 
becomes awfully slow if there are a lot of relations in view




> COMUNITIES
>
> on the wiki-page mentioned above the 'belgium' specification mention
> an administrative level 5 'comunities' (gemeenschappen).
> Comunities are about culture and people. Don't think one can map the
> communities in Belgium.

I think it has been discussed before. The areas where a community has 
powers are well defined. But look up some old discussion of this where 
we've discussed the constitution and everything for more details :-)

> It is an admnistrative level, but it's 
> something that cannot be mapped in a geographical boundary. In the
> list for admin_levels for boundaries it shouldn't be present.

Except that it is mappable, see the earlier discussion.

Ben