[OSM-talk] Rendering of Place Names in Mapnik

Scott Atwood scott.roy.atwood at gmail.com
Wed Dec 17 23:21:34 GMT 2008

How does Mapnik select which place names to render when the cities are close
enough that there would be label collisions in the rendering?  And is there
any good way of tagging the place name to give better hints about which
place names should have priority in case of collisions?
In particular, when I look at renderings of the California Bay Area at
various zoom levels, I see lots of poor choices for name collision

Virtually everyone would agree that San Francisco is the most prominent city
in the region, and should win any name rendering collision amongst cities in
the region.  Yet, at zoom level 6 and 7, Daly City gets rendered instead of
San Francisco.  Similarly, Oakland and San Jose are the next most prominent
cities in the region, yet at many zoom levels, smaller and less prominent
adjacent places get rendered instead.

Another related quirk is that some of these smaller place names are have
discontinuities in when then show in the zoom sequence, e.g. Mountain View
shows up at zoom level 6 and 8, but not 7, and Santa Clara shows up at zoom
level 7, 9, and 11, but not 8 or 10.

I'm sure this problem is not unique to the Bay Area, but it is merely an
example drawn from an area that I'm very familiar with.

Is there a good solution to this problem?


Scott Atwood

Cycle tracks will abound in Utopia.  ~H.G. Wells
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