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Unconnected ways and other data quality issues

Posted by amm on 12 September 2010 in English (English)

Increasing numbers of areas in OSM are starting to become "complete" or at least have a good coverage of the basic features. With this, the focus in OSM imho should increasingly move more towards "maintanance mode", ensuring that our data remains at the level of quality and up-to-dateness we pride our selves with.

So far, the majority use of OSM has probably been in webmaps and bitmap tiles, as it is a rather forgiving application with respect to data quality. Other areas that OSM is starting to push into, particularly routing, are less so. One particular aspect that is obviously very important for routing (and other applications), is connectivity or network topology. I.e. saying if one way is connected to another and if it is therefore possible to travel between them.

Unfortunately OSM seems to have a bit of a problem with connectivity and a surprisingly large number of roads and footways are drawn to end close by, but don't share a common node, i.e. meaning they are not connected. Luckily someone (was it Pascal Neis?) has made a great tool available through Geofabrik's OSM Inspektor to highlight all the roads and paths that end close (less than 1-5 meters) to another road or path, but aren't connected.

As you can see from the screen shot above, there are many of these nearly connected ways that need fixing! So let's all try and get those nearly connected ways connected and remove those red dots from the map! Head over to the OSM-Inspektor routing view and start fixing! The routing view is now available for all of Europe after only being created for Germany in the past.
Keepright, another great QA tool, between, has a similar check with its "Almost-junctions" check, and indeed several more really useful checks! So another good opportunity to fix those bugs.


As always, with any automated quality assurance tool, there will occasionally be false positives, where the way truly does reach very close but is not connected, as there might be a wall, fence or a 1000m drop preventing you to get from one way to the other. So please be careful and let the usual commen sense prevail when fixing these issues.

Watching the map evolve

Posted by amm on 18 September 2009 in English (English)

It is always fascinating to see all the different places around the world where people work on the this project and how constantly the map is evolving and improving. There are a couple of wonderful tools already that visualise this constant buzzing of the map. Of cause there is the much viewed and cited A year of edits 2008 video, but that is unfortunately a bit outdated by now. There are also the Osmaware scripts, that generate a set of kml files with which you can see all the people and where they edit the map every day overlayed on Google Earth or any other kml viewer. If you want to be even more up to date, you can watch OSM Live, which shows you the edits rolling in in realtime (well, with a 5 minute delay) all over the world.

However, although I really like osmlive, it only shows you the edits on a global scale and you can't zoom in. As most of the edits still happen in a tiny part of the world called Europe, zooming in really would be good to see where the edits occur. So I went along and hacked together a little java program that basically takes the ideas of osmlive, but visualises the edits on a zoomable slippymap. The program automatically downloads the latest minutely diffs and shows all nodes that have been added (blue), modified (green) or deleted (red) on the map as they occure. As it uses the new minutely diffs, the delay should be down to about 1 minute now.

If anyone wants to try it out, you can find the program at http://gpsmid.sourceforge.net/misc/LiveEditMapViewerJ.jar. Although it isn't really "useful" it is fun watching the edits as they happen and zooming in on them. Especially, if you manage to catch a whole new village just appearing in front of your eyes. :-)

Editing on the go

Posted by amm on 28 June 2009 in English (English)

When out and about, I often notice a small detail here and there missing in the map such as a post box or atm and of cause I want to add it. But by the time I have finished what ever I was actually doing (these aren't mapping trips after all) and could enter the POIs I have frequently forgotten about them again :-(. Anyone else has the same issue? So I have always wanted to be able to just take out my phone press a few buttons and the poi is in the database, after which I don't have to worry about it anymore.


Well, I have last week finally gotten around to start adding an on-the-go POI editor to GpsMid, an app to display OpenStreetMaps on any java enabled phone. It isn't much yet, and still needs quite a bit of work, but definitely is starting to become useful, at least to me. So I though I'd blog about it here, as others might find it useful too and I would be interested to hear feedback of what would make this feature most useful to others.


So how does it work? Well, first of all you need to make your self a GpsMidlet. As GpsMid is originally an offline app, all the map data gets stored together with the app in it's own binary format. For this, there is a little converter Osm2GpsMid that takes a planet extract, for example the UK extract from GeoFabrik and creates a midlet from the area you have selected, preferably city sized to not overload your phone. The resultant file is now ready to be copied over to your phone and installed. Once installed, you will be able to browse the map, or use a Gps to find your location. To add a POI to OpenStreetMap you need to move the cursor (screen center) to the location where you want the new POI. Then you can select the "Add POI to OSM" from the menu. This gives you a list of possible POI types from which you can choose. Once you have selected a type, you can still add an arbitrary number of other tags to the POI before uploading it to the OSM database. In addition to creating new POIs you can also modify, add or delete tags of existing ways. For example it is possible to add a name to an unamed way or correct an existing name, add a maxspeed restriction or remove a wrong oneway tag.


Altogether I hope this already has some uses, although it clearly is still early days and still has a bunch of caveats and usability issues that I hope to work on in the future. The main two problems of the POI editor I guess are the fact that map shows you the data from whenever you have downloaded the planet extract. So you might think a POI is missing when in fact it has been added in the meantime. The second problem is that this can even be your self, as GpsMid continues to show the old state even if the POI was added by itself. So regular map updates are recommended if you want to use the editor.


Anyway, in case you do feel brave enough to give this a try, download the latest nightly build of Osm2GpsMid, convert your area and start mapping POIs!


Feedback or questions are much appreciated.

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