[Talk-us] script for adding layer=1 to bridges

David ``Smith'' vidthekid at gmail.com
Thu Jan 28 01:47:17 GMT 2010

On Wed, Jan 27, 2010 at 9:01 AM, Bill Ricker <bill.n1vux at gmail.com> wrote:
> On Wed, Jan 27, 2010 at 2:13 AM, Frederik Ramm <frederik at remote.org> wrote:
>> > I've noticed that a lot of bridges don't include a layer= tag.  I
>> > suspect this is because they render OK in mapnik...but not so well with
>> > osmarenderer.  (Consider the railroad
>> > in
>> > http://www.openstreetmap.org/?lat=33.76931&lon=-84.53762&zoom=17&layers=0B00FTF.)
>> I'd suggest to modify Osmarender rather than the data, then.
> No this is  Tiger import data, the data arrived  wrong and was half
> corrected. (much of tiger has intersecting nodes where there should be
> bridges. some bridge insertion went without layering), It missing all but
> implied layering of bridge-nature. What we can't tell without checking
> satellite view is whether the bridge is at grade level with the Railroad in
> a ditch, or if the bridge pitches up over the RR.

I wouldn't put any faith in when TIGER says something is a bridge.  It
seems like, in the process of merging tiger lines into single ways, no
consideration was given to which segments were bridges.  As a result,
the entire length of the street gets "bridge=yes".  Furthermore, this
usually appears on roads with no obvious bridges (though there could
be a tiny culvert somewhere along it) and not on roads that have
bridges of any significant length.  As far as I can tell, it could be
completely random.

Anyway, I have seen places where people have cleaned up freeway
corridors, and neglected to tag "layer" on anything unless there are
bridges crossing over other bridges.  Mapnik renders this fine
(actually that could be considered a deficiency of Mapnik in my
opinion) but it looks a little goofy in Osmarender.  (On the other
hand, when one end of a "layer=0" bridge is directly at an
intersection with other "layer=0" streets, Osmarender renders this
beautifully and Mapnik makes it look odd.)  Since some people consider
the entire "layer" tag to be "tagging for the renderer" these people
probably don't think it's important to add thorough layer information;
instead, they add just enough to make it look decent in "the
renderer".  I am not of that opinion.

David "Smith"
a.k.a. Vid the Kid
a.k.a. Bír'd'in

Does this font make me look fat?

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