[OSM-talk] The Highway tags and other junk strikes back
guy at graviles-reynolds.org
guy at graviles-reynolds.org
Tue Dec 19 11:46:42 GMT 2006
Quoting matthew-osm at newtoncomputing.co.uk:
> On Tue, Dec 19, 2006 at 12:00:01AM +0000, Ben Robbins wrote:
> > >To sum up your position: Because I support drawing streets wider than
> > >they really are, it makes no sense for me to support making gates
> > >smaller than they are. Is this a correct interpretation of your
> > >argument?
> >
> > The point of a street being wider is so its clearer. So to go smaller is
>
> > less clear. Even if the node is to render a sybol or something where the
>
> > gate falls, that is less clear. Therefore it seems illogical to state that
>
> > something should be a node, becuase another segment is rendered wider. I'm
>
> > awair that your point is consistent in the extent that your saying that the
>
> > scaling in realitiy doesnt have to be 'exaclty' the same as on the map. I
>
> > would agree to that, but the scaling of gates, seems to be the oposite of
>
> > your example with the road.
>
> No, for this reason:
>
> You could tag, reasonably sensibly, like any of the following:
>
> a)
>
> *----road----*----road----*
> g
> a
> t
> e
> *----road----*----road----*
>
>
> b)
> *
> g
> a
> *----road----*----road----*
> t
> e
> *
>
>
> c)
>
> *----road----*(gate)----road----*
>
>
>
> (a) is like OS Mastermap - it is far too detailed for OSM currently, and we
> just
> can't currently compete in this level of accuracy, in my opinion. Maybe in
> the
> future, when common GPS units have the accuracy and detailed satellite
> imagery
> is available everywhere, but not now.
>
> (b) seems to be the way you are tagging.
>
> (c) is the "standard" OSM convention at the moment.
>
>
> The argument that you gave (there is an inconsistency about roads being
> wider
> [for readability] but gates being smaller) does not hold when a renderer
> that
> understands gates becomes involved. Current renderers do _not_ understand
> gates,
> and just put an icon over the road. This, I imagine, will be fixed over
> time.
>
> This is what happens when a road is rendered:
>
>
> *--------*
>
> becomes
>
> ------------
>
> ------------
>
> it could be scaled to make the map clearer:
>
> ------------
>
>
>
> ------------
>
>
> Now, imagine that a gate is a single node (here represented by g):
>
> *------g------*
>
> The _renderer_ can automatically scale this gate to match the road:
>
>
> ------*------
> g
> ------*------
>
> or, bigger for readability:
>
>
> ------*------
> g
> g
> g
> g
> ------*------
>
>
> However, when you tag like you do, the renderer has no choice. For a
> "normal"
> scale drawing (whatever "normal" is), you get:
>
>
> ------*------
> g
> ------*------
>
> but when roads are drawn larger to make them easier to see, you will get
> the
> following, because you have fixed the endpoints of the gate:
>
> ------ ------
> *
> g
> *
>
> ------ ------
>
> Similarly, for roads drawn smaller:
>
> ------*------
> ------g------
> *
>
I wholly agree, and if the gate is not on the main way ie in a boundary feature
abutting the way you would create it as:
------g------- Fence ------
| (track)
------*------- Road -------
the resulting render would be:
------------*gg*-------------
| |
| |
------------| |-------------
-----------------------------
and the gate would again grow or shrink in proportion to the render size of the
associated way.
Guy
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