[OSM-dev] Data source for robot

Apollinaris Schoell aschoell at gmail.com
Tue Oct 12 18:16:19 BST 2010


On Tue, Oct 12, 2010 at 6:46 AM, Peter Budny <peterb at gatech.edu> wrote:

>
>
> Road routes are useful because it avoids the dreaded semicolon (as
> someone else called it).
>
>
agreed this is useful. but it's not the whole story


> For instance: I would love to see the correct symbol for roads on the
> map--an Interstate shield, a US Highway shield, or a State Road shield
> with the shape of the state.  In a road relation, a URL to this is
> stored in the symbol=* key.  The renderer would just find all the road
> relations a way is part of, grab their symbols, and place them on the
> map.
>
>
many wanted to see it but no one to date has implemented a usable and
scalable version of it. If someone does this adding the relations makes
sense. until then it's not of much use.

Currently no renderer supports this.  They draw ovals and put the ref=*
> inside, which would be okay... except that they don't support
> semicolons.  What they /should/ do is split the tag by semicolons, and
> place all the resulting tags on the road individually.
>
>
This is not trivial if there are multiple routes on the same way. I have
done it once for Garmin maps but the need to prioritize and add the shields
based on space on a map is really not that easy. no matter if you do this
with ref on the way or with relations this is tricky. even more so with
relations because they are not sorted and a renderer needs to build a sorted
db first. splitting ref tags with semicolons is much simpler.


> What they /actually/ do is try to place a giant ref=* tag inside the
> oval, which usually means giving up when you have "ref=US 29; US 78; US
> 278; GA 8" (and that's assuming you don't use the long US:US and US:GA
> format).
>

Relations are the cleaner solution here.  You /could/ accomplish the
> same thing with regular tags, but who wants to see symbol=*, symbol_1=*,
> symbol_2=*, etc. on every way in a city?  (Or worse, a giant symbol=*
> tag with semicolon-separated URLs?)
>

this is all theory until someone builds a renderer. then it's time to
discuss how this can be supported with tags in osm.



> --
> Peter Budny  \
> Georgia Tech  \
> CS PhD student \
>
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