OSM Weekly Review – Mooses on Rails

The talk of the town this week has been the long awaited Ruby on Rails port. A developer’s meeting in Oxford on Saturday gave the opportunity to finish off some loose ends in the existing Rails code, integrate Potlatch, as well as experimenting with PostGIS. Version 0.1 of OpenStreetMap was written in Java, then re-written in Ruby and over the last 6 months all the server code has been ported to Ruby on Rails. The good news is that the new site has been deployed and is running. There have been some teething problems, so if the site is unavailable when you take a look (if you get a 500 error), come back in half an hour or so. Because the way that the API works in 0.4 is slightly different from 0.3, applications that use OSM will have to be updated. To use OSM 0.4 with JOSM, you’ll have to download a new version from the JOSM homepage. Other apps like Tiles@Home and the Applet are being updated and users should check their wiki pages for updates. There’s going to be an OpenGeoData post dedicated to the Rails Port later on this week – so stay tuned.

Anyone who reads OSM-Dev or OSM-Talk will have experience the "we should use PostGIS" scenario. The familiar story has taken a new twist with Robert Monro, Schuyler Earle and others working on bringing the benefits of PostGIS to the OSM Rails port. PostGIS is a spatial database – a sort of swiss-army knife for all things geospatial. It can suck in numerous formats of spatial data, and speeds up spatial queries like "what is next to here?" or "what is inside this box?". A major problem with using PostGIS has been its lack of support of Topology. Topology is about connectedness – what connects to what and what, what side of A is B on – and OSM’s database is topologically constructed, which has limited the usefulness of tools like PostGIS. By writing customised functions for PostGIS, SDE and Robert Monro hope to get around the problems with PostGIS whilst maintaining OSM’s data model. There is more information here and source code here.

Devout countryside man, Nick Whitelegg, brought this post to the attention of the mailing list. It seems that a lot of walkers don’t see the value of OSM and have a "if its not complete I don’t want to know" attitude – something that rings true of a lot of people that OSM users encounter. Mikel makes a good point that the continued mapping of the countryside by the OS is currently far from guaranteed. If walkers want up-to-date maps they are either going to have to pay a lot more for them, or get them from other sources. If you are a walker or countryside user, take a look at Free-Map, which provides editable maps optimised for countryside users, based on OpenStreetMap data.

A rainy bank-holiday weekend in the UK isn’t great news for most people. For OSM users it meant one cool new tool and one interesting use of a wiki page. The cool new app is David Earl’s name search, which runs off OSM data. The search algorithm is impressive, to say the least. Try searching for your local pub – actually that’s a bit easy – try putting the tool to the test. Prizes for the most bizarre, correctly returned search posted to the comments of this post.

Are you the Moose? Take the OSM Purity Test and find out.

By Nick Black