[OSM-talk] Maximum recommended length of ways tagged with layer

colliar colliar4ever at aol.com
Sat Mar 22 14:33:03 UTC 2014

On 22.03.2014 11:01, Richard Z. wrote:
> On Fri, Mar 21, 2014 at 05:05:21PM -0500, Paul Johnson wrote:
>> On Mar 21, 2014 4:59 PM, "Richard Z." <ricoz.osm at gmail.com> wrote:
>>> Example of a problem this should catch: I have seen cases where someone
>>> wanted to tag a simple bridge with layer and added the layer to the wrong
>>> segment - tagging a hundred or more miles of road accidentally, possibly
>>> affecting crossings far away for an area not downloaded. The validator
>> will
>>> not detect it and in most cases the renderer will work around this bug
>> very
>>> well so it is only discovered by accident in most cases.
>>> This is not limited to layer, I have seen the same problem with culverts
>> and
>>> bridges.
>> This seems like something a validator should be able to catch without
>> overly complicating how levels work.
> I am not trying to complicate how layers work right now but trying to codify
> how they already work in >99% of cases in easy to follow rules that could be
> utilised by validators.
> Yes, the validator should be able to catch such situations. Just how? 
> It doesn't right now. I see some possible approaches:
> * warn user if tagging excessively long ways with "layer". Here the problem
>   is to judge what is excessively long.

As judgement is difficult and it will still depend on other cases, I do
not think this will help that much

> * warn user if applying layer to a way that exceeds the size of downloaded area
>   because in this situation the validator is unable to do even the basic checks.

even though this will lead to false warnings when working with
incomplete data, I would give this solution a try.

> * warn user if applying layer to a way without tunnel/bridge/covered/indoor or
>   similar tags.

Covered is an example where it does not work e.g. you tag the
building=roof with layer and not the way underneath.

Still for other tags (bridge/tunnel etc) this would be helpful.

> There is more than just JOSM and all should follow the same rules so ideally 
> this rules would be nicely documented in the wiki.


Note, JOSM would almost be able to use the list right now, already.

>>> What kind of underground areas are that in Kansas, do you have a pointer?
>> I'm not exactly sure where exactly it is, but there's apparently a pretty
>> extensive underground industrial and office district entirely underground
>> complete with drivable underground streets in KCK thanks to repurposing an
>> old mine.
> interesting, I will have a look when I have some time.

Could you post a link, please. I wonder how mapnik will work with that
as there are already problems with a single underground floor/parking.

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