[OSM-talk] The Highway tags and other junk strikes back

[guy at graviles-reynolds.org]

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