[Talk-us] Newly tweaked TIGER road names tiles

[Toby Murray]

As we briefly discussed during the virtual mappy hour last week, I
have managed to wrangle some TIGER data and do some automated
expansion of abbreviated street names on the TIGER road name tiles.
The results can be seen in a new tile layer. You can preview it here:
http://tile.osm.osuosl.org/tiles/tiger2012_roads_expanded/preview.html#17/37.79816/-122.24627

I just added the appropriate URLs for the new layer to the TIGER 2012
page on the wiki so you can use them in JOSM and Potlatch as well:
http://wiki.openstreetmap.org/wiki/TIGER_2012

Since this is a brand new tile layer, nothing is cached in the CDN so
requests might be a little slower than normal at first.

I am fairly certain about the accuracy of the process and the checks I
have performed all came back with good results. But of course TIGER
being such a large and varied data set, there might be an odd edge
case lurking somewhere so it would be great if some people could check
their areas and make sure they don't see anything odd.

The other tweak I made after a suggestion from Ian was to draw the
tiles in two layers. One drawn first with only lines and then another
layer with only names on top of it. This means that road names will
always appear on top of road lines. This avoids roads obscuring names
and improves readability.

Technical details: This was *not* done by doing simple string
matching. I downloaded all of the "Feature Names Relationship" files
which contain separate fields with codes for directional, type and
qualifier prefixes/suffixes. Then I composed the name one element at a
time from these fields. This gave me a mapping from TLID to expanded
street name which I then imported into a new column in the existing
table that is used to render the tiles. Then it was just a simple
matter of telling the mapnik style to look at the new expanded name
column.

Toby