[OSM-talk] Keep Mapnik relevant

Andy Allan gravitystorm at gmail.com
Thu Jan 8 08:10:13 GMT 2009


On Thu, Jan 8, 2009 at 7:19 AM, Andreas Fritsche
<andreas.fritsche at gmail.com> wrote:

> I don't get it.

Really? It's pretty straightforward.

> You still know it's a railway, a highway, a
> building, ... . Reading more tags will unveil the name, the operator,
> the source and so on. There is no difference to a possible 'removed'
> -tag. We've alway had certain key-tags that give clues about the type
> of an object, others define properties. An easy example would be the
> pair highway and name.

Right, so have a look at the following.

highway = primary => I have a primary road
name = Foo Street => I have a primary road that's called Foo Street
ref = 58 => I have a primary road with ref 58 that's called Foo Street
abandoned = yes => I don't actually have a primary road at all.

Do you see how the last one is completely different? If we start
tagging things like this, then there's no way of telling what's a
primary road without understanding *all* other tags. It's not just
abandoned, there's also construction, historical, removed and so on.
So it's a convention (and a pretty straightforward one) to only use
highway=primary on things that are *actually* primary roads. Only use
railway=rail on things that are actually railway lines. Using
highway=primary on something that is no longer a primary road is just
a complete PITA for everyone, mappers and renderers and all other
applications included.

Cheers,
Andy




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