[OSM-talk] Updated redaction oneway map

Toby Murray toby.murray at gmail.com
Fri Aug 17 05:49:25 BST 2012

On Mon, Aug 13, 2012 at 11:51 PM, Toby Murray <toby.murray at gmail.com> wrote:
> On Mon, Aug 13, 2012 at 1:34 AM, Toby Murray <toby.murray at gmail.com> wrote:
>> I just updated my "oneway" map that shows ways with a oneway tag but
>> without a highway tag that were last touched by the redaction bot. I
>> have been updating the tiles every couple of days but at the
>> suggestion of someone on IRC I just added bridge and lanes tags to the
>> list in addition to oneway. The world is rendered to z10, most of
>> europe to z11 and specific high density cities to z13. (Several places
>> in the US, Europe and Australia) If you want a specific area rendered
>> to a higher zoom, feel free to send me a bbox.
>> If you use these tiles as an imagery layer in JOSM as suggested at the
>> bottom of the page, be sure to flush your tile cache for that layer
>> every couple of days to pick up changes. (right click with this as the
>> only visible imagery layer and select the "Flush tile cache" option)
>> I can see the .osm file I render from shrinking every time I update so
>> progress is being made! It started at over 10 MB and was about ready
>> to go under 5 MB when I added the additional tags which put it back up
>> over 6.
>> http://ni.kwsn.net/~toby/OSM/maps/redaction.html
> Earlier today I noticed that I had a slight error in my rendering
> rules. I added bridge, lanes and tunnel to the list of queried tags
> but not to the rendering. So I just uploaded a new set of tiles with
> fresh data (as of a couple hours ago) and the new rendering rules. So
> there may be additional problem ways to check now.

Well I took this as an opportunity to learn about renderd and mapnik.
As of a few minutes ago, I am rendering tiles for this map on demand
using mapnik. This means that you can zoom in as far as you want
anywhere in the world. The style has changed slightly, especially at
low zoom.

It might be a little slower especially if several people are hitting
it at once. I'm using mapnik to render straight from a .osm file. This
is extremely handy and makes updates as trivial as uploading a small
file to the server. However one limitation is that I can only run one
rendering thread. The mapnik .osm input plugin is not thread safe and
causes renderd to segfault immediately if I set it to more than one
thread. I might tinker with it some more at some point to see if I can
get it rendering from sqlite or something. But since I'm only dealing
with a small data set, it should be pretty responsive even with a
single thread. I figure by the time I tweak everything to be just
right, all these bot problems will be fixed! :)

Right now we're sitting at 3,076 ways left to fix. And keep in mind
that for every way rendered on this map, there are probably 10 more
bot problems in the area like missing ways, broken topology, etc. So
don't just fix what is highlighted and move on, take a look around and
smell the nodes.



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