Last week I was at the yearly FOSSGIS conference, the German language conference for Open Source GIS, Open Data and OpenStreetMap. This year it took place in Rapperswil, Switzerland near Zurich. I like the relaxed atmosphere and the good mixture of introductory talks and talks for power users.

The yearly FOSSGIS conference, the German language conference for Open Source GIS, Open Data and OpenStreetMap, will take place from June 12th to June 14th 2013 in Rapperswil, Switzerland near Zurich.

It is high time I’ll write something about the status of the Wikipedia Multilingual Maps project I have been working on for many months now.

After setting up the MapQuest Render Stack and poking around in its code I consider using it for the Multilingual Maps project. Unlike Tirex it can run on a cluster of machines for reliability and load distribution. That will be important for a tile server working on “Wikipedia scale”.

Whatever way we’ll develop for rendering the multilingual tiles, we have to get the information about which language(s) the user wants from the user to the tileserver. Web browsers typically support the selection of an ordered list of preferred languages. This list is sent through the Accept-Language header to the web server. We could use this setting to determine the language for the labels. But in some situations people might not know about this setting or can’t change it. Maybe they are sitting in an Internet cafe in a foreign country. In that case it might be easier for them if they can just change the language setting on the web page. This is especially interesting if the web site knows which languages are available and only shows those options. The browser setting doesn’t know anything about actually available languages, it just has one large master list.

If we want to render multilingual maps by separating the “label layers” from the “base layers” as described in my last blog post, we have to make sure the rendering results don’t change. Or, at least, that they do not look too bad. Lets look into that.

As a proof-of-concept for the rendering of labels on demand I set up an OpenLayers map with two XYZ tile layers, one for the background and one for the labels. I configured the MapQuest render stack to deliver those two layers, the background layer is stored in the tile store, the label layer is never stored, but always rendered on demand.

Nearly everybody setting up an OSM tile server uses either the Apache/mod_tile/renderd or the Apache/mod_tile/Tirex combination. The renderd software has been around for while. When we needed something more flexible two years ago, Frederik Ramm and I created Tirex. To keep the development work needed small and make it easier to switch from renderd, Tirex uses the same Apache/mod_tile frontend as renderd. We had plans to add different frontends, but they never materialized. Apache/mod_tile is difficult to configure and not very flexible, but it does its job well enough. I wrote a proof-of-concept frontend using node.js, but that was never taken up either.

In Choosing a Language I have proposed to think about how to render labels in different languages into the tiles on the fly when they are requested.

One key issue of the multilingual map project is obviously how we choose which language labels to render into a map. There are two sides to consider:

(This article is a (modified) translation of a German language article I wrote for the German OpenStreetMap blog. It should have been translated months ago, but I am only now getting around to it. The project was a bit slow in starting but is gathering momentum now. It has progressed a bit since the original article.)

Next week is the FOSSGIS conference in Dessau. I’ll be speaking there about OpenStreetMap in Zahlen und Karten and Das Osmium-Framework. Together with Tim Alder I am also organising a community session to discuss the Wikipedia Multilingual Maps Project. See you in Dessau!