Since March the OSMData Service has been running on new servers sponsored by FOSSGIS e.V. I wrote about the switch in an earlier blog post. Now, half a year later, I want to write about my experiences with the new setup.

For many year now I have been running a service at <a openstreetmapdata.com, first alone and then with the help of Christoph Hormann. We offered processed OSM data for download, most importantly coastline and Antarctic icesheet data. And although the service was always free to use and the software mostly Open Source, this was always our show. For a long time I wanted to change this and turn this into a proper OSM community project, and, finally, we have taken a big step towards that.

I just added a few features to taginfo: There is a new “Similar” tab on all key pages, see for instance all keys similar to the “highway” key. This makes it easy to find related keys and typos. The new Similar keys report shows keys that are commonly used together with similar keys that are rarely used. Often, but not always, the rare keys are just misspellings.

I have been writing lots of software for the OpenStreetMap project and there is always one problem: How to test it? There is a huge variety of data in OSM, every conceivable way of tagging, every way of getting the data slightly (or not so slightly) wrong, will sooner or later appear. We need to test file formats, OSM objects syntax and semantic, changing data, cases with failing referential integrity or invalid geometries and much much more. But just coming up with all those test cases is a huge task and implementing those tests is even more work.

On January 16 2014 I will give a talk about the OpenStreetMap data model at the HafenCity University in Hamburg. The talk will be in German. Everybody is welcome to attend, you don’t need to be a student there.

I have written before about my work on the software doing the assembly, repair, and conversion of the OSM coastline data. I wrote the Osmcoastline software and I run it daily to create shapefiles with land and water polygons available for download on OpenStreetMapData.com [Update: Discontinued June 2019, now available from osmdata.openstreetmap.de]. For a while this data has now been used on the main OSM map. Unlike with the old process, this new process usually makes sure the map is updated within a few days when the coastline changes.

OpenStreetMap doesn’t allow multiple tags with the same tag key. But there is a believe out there in OSM land, that you can work around this by putting all the tag values you want into one tag using semicolons as separator characters. So if there is a bank with an ATM machine, people tag [amenity=bank;atm]. Or there is a road with several refs, then they tag them as [ref=I 70;US 40] and hope that it will magically work. And it does work in some cases. But in many cases it doesn’t. Let’s look into this a bit.

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.

A year ago I released the first version of the OSMCoastline program that extracts and assembles coastlines from OSM data. Since then I have learned more about coastlines in OSM than I ever wanted to know, fixed numerous coastline bugs myself and added more features to the software. OSMCoastline has been in production use at Geofabrik and the German map server for more six months now.

I have written before about the mapping of Antarctia in OSM. Since then there has been a lot of activity. Christoph Hormann has prepared better Antarctica data for import and has documented the planned import extensively on the wiki. Peter Körner has created a web map in Polar Stereographic Projection.

OpenStreetMap wants to map the whole world, but there is a whole continent that has been neglected a bit: Antarctica. Of course there isn’t much there besides rocks, ice, and penguins and not too many people live there. But still, it is a huge area and it should appear properly on our maps.

One of the biggest problems with the OSM data model is that there are no real polygons. Polygons or multipolygons are “simulated” using closed ways or multipolygon relations and several other methods. These multipolygon relations are often broken. Some of the problems resulting from this non-existence of multipolygons are affecting many people, for instance with broken coastlines and country or other boundaries.

In a recent discussion on the OpenStreetMap talk mailing list around imports in France a point came up again that has been raised a few times: If we had some notion of layers in OSM data, maybe, some tasks such as imports would be easier or could be done in a better way. I want to look into this “layer” issue a little bit.

Osmium has had support for assembling multipolygons from relations for a long time. But the code had been lifted from an earlier Geofabrik project and was rather messy, hard to extend, and it contained several memory leaks. In the last month or so I finally chewed through the whole thing bit by bit and made it prettier.

Every map of the world has to take into account that there are land areas and water areas. You could have huge polygons for each continent and paint them on a blue background. But handling those huge polygons is difficult. OpenStreetMap solves this problem by having ways tagged with “natural=coastline” and the convention that the land is always on the left side of this way. So a continent or an island is surrounded by one or more ways in counter-clockwise order. It is much easier to edit those coastlines instead of large multipolygon relations or something like it. Coastlines are the only case where OSM has this special rule.

More and more boundaries of administrative areas find their way into OpenStreetMap. In some countries there is already quite a lot of data for several levels of government. Unfortunately it is hard to edit and hard to use because relations must be used to model areas in OSM and relations are notoriously difficult to handle. Relations and with it the areas they represent are often broken as a result. Its therefore hard to get a complete set of administrative areas for a particular country and level of government.

The OpenStreetMap database currently contains nearly 900 Million nodes. Because some nodes have already been deleted the highest node ID is already past 1 Billion. IDs in the database are already 64 bit wide so that space will not run out. But lots of software only uses 32 bit IDs. There recently was a question on the German mailing list when the 32 bit would run out, so I want to give some answers here.

On the weekend there was (again) a discussion on the German OpenStreetMap mailinglist about how the system of coming up with new OSM tags and better defining existing tags could be improved (or whether it actually needs improving). This is a difficult subject. The “system” (for lack of a better word) is confusing and often leads to frustration. But it does basically work. OSM is growing, people are entering more and different kinds of data, usable maps are produced, finding routes based on OSM data works.