[OSM-talk-be] abandoned railways

[Lennard]

Luc Van den Troost wrote:

> Perhaps you can explain how 'abandoned' and 'disused' SHOULD be
> interpreted in relation to the rendering rules. As far as I have seen,
> the wiki pages about railways do not mention this. 

I can only explain at the moment how these situations handled on the 
mapnik map. How they *should* be shown, is another matter. Opinions 
differ. Personally, I don't need to see a (former) railroad on the map, 
when the tracks are physically gone, especially if it's converted to a 
cycleway.

> If both should appear on the map, then probably 'historical tracks' that
> are no longer visible should not be mapped, or at least not this way. 

Currently, mapnik renders railway=disused/abandoned/construction all 
with the exact same style: a dotted line.

> Historical items then might be mapped in a different way that is usefull
> for, for instance, a separate rendering or different layer. That would
> not only be the case for historical railway tracks, but as well for
> historical city walls, canals, gates, old river quai and docks, ... that
> all have influenced city development. But that is another discussion.

Hard to solve, unless *every* data user starts to understand and process 
something like date_start/date_end tags.

> Another 'historical' point is that it is a pitty that OSM doesn't offer
> a kind of 'time-machine'. On one side it would be nice to see the growth
> of OSM that way, on the other side the map we are currently making will
> be historical one day. If - for instance - Doel would be broken down for
> harbour expansion, going back in time then would show how it was before,
> same would be if the 'hedwigepolder' on the other side of the border
> would be flooded again. But again, that is just a side remark and
> another discussion.

Don't forget the Prosperpolder, where works are already under way to 
open it to the Schelde. I fear the infrastructure needed to store, 
process and show OSM as it was in a particular point in time, is not 
easy to construct. The sheer data volume means you need quite some 
processing capacity, both in CPU and storage.

-- 
Lennard