[OSM-talk] cadastre, ways, rendering

[Dirk-Lüder Kreie]

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Marcus Bauer schrieb:
> On Tue, 2007-01-23 at 16:13 +0100, Kristian Thy wrote:
>> On Tue, Jan 23, Marcus Bauer wrote:
>>> That's the reason why ways shouldn't be too long. I.e. for a motorway it
>>> is a good idea to start a new way after each exit. The renderer will
>>> then produce nice maps (and that is what it is all about):
>> IMO, changing the data to suit the renderer is tackling things the wrong
>> way around.
> 
> Until renderers have artificial intelligence, they will need some help
> to make decent maps. 

yes, that's why there are separate tags like osmarender:renderName=no (I
don't know if there is a similar tag for "ref")

> Have a look at this:
> http://www.openstreetmap.org/index.html?lat=43.67615439303823&lon=7.207250585123151&zoom=11

I don't see the problem.

> To avoid this you either add more and more rules to the renderer, ad
> infinitum, or you help it a bit. You don't loose any information if only
> one side of a motorway has a ref=A5 key/value.

Yes you do, because there is no way any software does know these 2 ways
belong together, or it would have to guess, and software that has to
guess works oftentimes, but sometimes this goes horribly wrong, and that
could be easily avoided by properly tagging every way.

> If a highway has more than one ref, like A8/E88, it makes sense to
> alternatingly tag ways, i.e. one section of a highway A8, the next E88.
> You will always have more information to put into the map, but it
> doesn't get better and isn't even of use for later routing, as long as
> it is tagged motorway.

For that Motorway the correct way to tag it would be ref=A8 int_ref=E88
not any form of alternating.

> Another example: how do you make curves? Actually you add points until
> it nicly renders at higher zoom levels. So in a certain way you "change"
> data to suit the renderer.

In my opinion thats dangerously wrong.

> The point is to find a good compromise. 

No, to be useful in other applications than rendering maps the data has
to be as complete and accurate as reasonably possible, and the renderer
has to deal with leaving out data (which *currently* does not happen at
all in the case of osmarender and only road names in the case of Mapnik
IIRC, unless specifically told to by some tag in the data)

It's always easier to leave things out later than having to guess
missing data.

Dirk-Lüder "Deelkar" Kreie

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