[OSM-talk] Overlapping objects which should both be there

[Andreas Barth]

* Sebastian Spaeth (Sebastian at SSpaeth.de) [080526 15:06]:
> Andreas Barth wrote:
> > sometimes, e.g. in this map
> > http://openstreetmap.org/?lat=48.0823&lon=12.0469&zoom=14&layers=B0FT
> > two objects overlap in a way that doesn't represent reality adequate.
> 
> So, how do you plan to represent reality at any scale, when you can only 
> scale down to a pixel on your map?

By dropping unnecessary elements at larger zoom levels - which is how it
is done already today.


> What do you propose? To make the railway overlap the road (which would 
> be just as bad)?

Changing the order of overlaps doesn't help, agreed.


> Or to move the railway to the side, so that it is next 
> to the road?

Basically, by moving both the railway and the road a bit to the side, so
that they both can be drawn on the map.


> How much moving around do you want to do when there are lot 
> of things next to each other?

I don't propose to move objects in every case - there are enough cases
where overlapping is sensible (like e.g. city names overlap roads /
...). Also, overlapping in case of a junction (or similar) is sensible
as well.

This is only relevant for cases where both objects run more or less
parallel for a longer distance - especially as the human eye tends to
ignore overlapping in case of crossings (that's normal to us), but not
in case of parallel runnings.

So, I don't expect too many cases where there are too many things in
parallel - at least I haven't yet seen any case, whereas I have seen
many cases where it would've easily been possible.


> > - but shouldn't the map just look great on every zoom level? If so, how
> > about auto-moving objects only during the presentation on the rougher
> > zoom levels (if one zooms in, things start to be more exact, which
> > exactly represents what one would expect)?
> 
> How is moving things away from where they really are much more precise 
> then draw them overlapping?

Please keep in mind that I don't propose to change the database. I just
propose to change how the outcome looks.

To whether that's more precise: That depends how you view the map (that
might be a difference between us): If you look at "how can I get
around", then yes, it is way more precise. And in case you want to know
"how much space is there", you'll soon need to use a zoom level that is
detailed enough that moving doesn't happy anyways anymore.


> If you have 10 roads/railway lines next to each other, is moving each
> of them to the side ok?

I haven't yet seen such a place.

Ignoring that, of course there should be a "maximum movement" set.


> It's not that easy, is it?

I never said it's easy. Not being easy doesn't though translate to
"shouldn't be done".

(Basically, one shouldn't move the stuff around, but use some bijective
continuous transformation on the coordinates - that will avoid the
neighbouring objects get hit too bad.)


Cheers,
Andi
-- 
  http://home.arcor.de/andreas-barth/