[Tagging] layer=-1, rivers, bridges and tunnels

André Pirard A.Pirard.Papou at gmail.com
Fri Apr 4 19:41:56 UTC 2014


Hi,

Regarding normalized layers.
If I can believe my eyes, bridges/culverts are under (uninterrupted
foil) roads
<http://www.hdtimelapse.net/content/HDtimelapse.net_City/HDtimelapse.net_City_3290_hirez.jpg>: 
bridge=road-1.
Unless a renderer must assume that, which should be stated in the wiki,
then bridge=road.
If I can believe my eyes, 90° crossing rivers/roads run under bridges,
that is river=bridge-1.
Unless a renderer must assume that, which should be stated in the wiki,
then river=bridge.
A friend of mine says that we must start counting at 1 (like year 1) and
hence that ground=1 (;-)).
I'd like to know how many of you agree.  While waiting, let's assume
ground=0.

Hence, it depends very much on what the wiki states and we should settle
that before discussing.
Assuming assumption, we have road=0, bridge=0, river=0.
If the renderer does not assume anything we have road=0, bridge=-1 and
river=-2.

On 2014-04-02 10:15, Pieren wrote :

> On Wed, Apr 2, 2014 at 8:32 AM, Andrew Errington
> <erringtona at gmail.com> wrote:
>
>> I have discovered a bunch of rivers and streams with layer=-1 in my
>> local area. In my opinion this is simply wrong,
>>
> It's not wrong. It's just another way to use the tag layer. I't not
> because other contributors don't share you opinion that they are wrong.
>
> Pieren
>
Quite right. Everything is relative (Einstein). What is certainly wrong
is threatening to change what others have done without warning (I won't
quote those threats).  That's called vandalism and, if the victim fights
back, a war.
And all in all, that makes OSM a very bad reputation.

> L’exemple fournit par OpenStreetMap révèle une série de dimensions
> intéressantes en matière de production de données géographiques sur
> base participative. D’une part, il permet la mise en place d’un vaste
> réseau de volontaires qui contribuent à son développement et à son
> utilisation, d’autre part, il pose une série de questions et soulève
> d’importants enjeux en matière de qualité et de validité des données.
> Ce système trouve un équilibre entre le développement d’une
> information géographique sur base participative et une qualité des
> données et des métadonnées qui n’est pas forcément l’équivalent de
> celle présente dans la chaîne de production proposée par les pouvoirs
> publics. En outre, en raison de ces enjeux de qualités, un problème
> d’interopérabilité émerge de façon récurrente.
>
(translation here
<http://www.papou.byethost9.com/PDF/PSGW/axe4.html#mozTocId81246>)
That was written by the Belgian government. While being very respectful
of "OSM volunteering", they very politely regret a quality level "not
equivalent" to their expectations (their own data), interoperability
problems, and, in other statements, data security, understand danger of
vandalism.
This very much affects the data we can get in return of what we can offer.

side note:

On 2014-04-02 15:56, Richard Z. wrote 
> yes. It should be done with sensible presets, we can not change the
> defaults for features that are already in use for ages.
Indeed, a few even resist the metric system ;-)
US press: the Bluefin-21 can dive 14 763 ft deep (in fact, 14 764 ;-)).

Cheers,

André.



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