[OSM-talk] Divided roads proposal

[Richard Weait]

On Mon, Dec 7, 2009 at 7:34 AM, Steve Bennett <stevagewp at gmail.com> wrote:
> Can renderers improve their render quality at lower zoom levels by not
> rendering (certain) link roads? Ie, given road A-B-C, with incoming road
> D-B, and link D-A, perhaps it could not render D-A.

Cartographers (people) can do most anything.  Renderers (software) are
pretty good too.  ;-)

In Mapnik, for example, you could select by zoom-level to either
render or not render all highway=secondary_link.

This is a rendering rule from Mapnik for secondary_link (secondary as
well) when zoomed all the way in (from 1:1000 to 1:5000). It shows
that the secondary_link will be rendered as 17 pixels wide.  Zooming
out causes the width to reduce to 12 pixels, 10 pixels, 4 pixels then
disappear at scales beyond 1:150000

    <Rule>
      <Filter>[highway] = 'secondary' or [highway] = 'secondary_link'</Filter>
      <MaxScaleDenominator>5000</MaxScaleDenominator>
      <MinScaleDenominator>1000</MinScaleDenominator>
      <LineSymbolizer>
        <CssParameter name="stroke">#a37b48</CssParameter>
        <CssParameter name="stroke-width">17</CssParameter>
        <CssParameter name="stroke-dasharray">4,2</CssParameter>
      </LineSymbolizer>
    </Rule>

You could easily choose to not show secondary_link at scales of your
choice.  Whether that is an improvement in rendering quality or not
would be a judgment call and should consider the intent of your
rendering and the interests of your audience.