Author Archives: Nick

OpenAerialMap – Community contributed aerial imagery

By Nick Black

The recently back-from-the-brink-of-death Slashgeo, links this morning to an interesting open geodata initiative – OpenAerialMap. As the name suggests, OpenAerialMap is an attempt to aggregate as much free aerial imagery as possible. This makes a lot of sense. In the same way that I can go out with a GPS and map my street, I can fly my UAV over my street and gather imagery, safe in the knowledge that my neighbour a few streets away is doing the same thing. We join it all up and get a free image map of the world.

A technical problem to solve will be to rectify images to make them usable with other mapping/GI systems. This requires the use of ground control points, either gathered from existing maps or imagery (as seen in the MetaCarta rectifier) or based on GPS positions. Right now, OpenAerialMap have opted for a one at a time approach – with users uploading an image and manually rectifying it – presumably against public domain, or maybe even OpenStreetMap maps. None of this is actually up and running yet – the project is still in the planning stage.

The licensing of the project is unclear – there’s a lot of talk about freedom and open source, but nothing concrete about what the license actually is. Aa OAM haven’t started accepting uploads yet, there’s still time to choose a license that will maximise the usefulness of the tool they are creating.

As you would expect, OpenAerialMap talk a lot about community on their wiki. Unfortunately, as of this morning editing the wiki has been frozen temporarily until we clearly define appropriate use. So in the mean time, you can subscribe to the mailing list to find out more.

A new advertising model for OpenStreetMap

OpenStreetMap is now featuring adverts from a new location based advertising service, Mappam. Just like the old banner ads that OSM used to carry, the location based adverts will go away once you have logged in. Unlike the old ads, Mappam ads take up very little space – there is only one advert on the map at a time, and it only takes up 16×16 pixels. This means more space for the map and more relevant adverts for OSM users.

Just like with the old ads, all the revenue from advertising goes straight the OSMF Treasurer and for a trial period the advertising broker is not taking any of the advertising revenue.

OSM’s Steve Chilton in a Very Special Podcast

For those of you who don’t follow the excellent Very Spatial blog, they recently featured OSM’s very own Steve Chilton in a podcast (mp3). Steve talks about OSM and about the upcoming State of the Map conference. Well worth a listen.

If you haven’t got you tickets for the State of the Map yet, you can sign up here. Tickets are limited and are dissapearing fast, so sign up now to avoid disappointment.

Ed Parsons (Geospatial Technologist EMEA, Google) to keynote at SOTM07

The OpenStreetMap Foundation are pleased to announce that Ed Parsons will be delivering the Keynote presentation at the State of the Map 2007, on Sunday 15th July 2007. Ed is a well known and respected figure in the geospatial community, whose long-term interest in OpenStreetMap is know to many. In his new position as Google’s Geospatial Technologist for Europe, Middle East and Africa, Ed is in a unique position to talk about OpenGeoData. His talk is titled “The Cathedral and the GPS – a personal view” and promises to be a highlight of the action packed SOTM07 weekend.

If you still haven’t registered, visit this page.

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

OpenStreetMap – Weekly Review

Lint is a tool that checks for errors in C code, taking its name from fuzzy fluff that accumulates around us, getting in our way and making us sneeze. Map’s have lint too; misplled tgs, orphan segments and untagged ways all cause problems when people want to use OSM’s data. Maplint does for OSM data what Lint does for C code, it looks at an OSM XML file and generates an error report, which can then be rendered by OSMarender, giving visual clues to the location of rogue data:

The Maplint Layer In

With the extension of the Tiles@Home server to support multiple layers, Maplint reports can now be viewed at There’s also a plugin for JOSM – JosmLint – that will highlight potential errors whilst you are editing a map, which can be downloaded from here.

Wii have an interesting approach to mapping underground networks developing on the dev mailing list. GPS units are pretty lame underground, and there haven’t been many volunteers to survey the Blackwall Tunnel on foot. A solution being discussed at the moment is to use accelerometers to detect motion and produce a map, specifically the motion sensors that are integrated into the handset of the Nintendo Wii console. The handsets also have integrated Bluetooth, meaning that they could communicate with another device that is connected to a GPS, and through the use of a process like Kalman Filtering, could produce usable results. This is very much a theoretical discussion at the moment – but highlights the inventiveness and resourcefulness of the OSM community. Read more here.

Nick Whitelegg has produced a browser-based editor for OSM data using the new vector support features of OpenLayers. The modest developer begins his mailing list post, “Not that the world needs yet another OpenStreetMap editor…”, if this is what you are thiking, think again. This is the first time that we have had a browser-based tool that can edit OSM-data without requiring the installation of additional plugins, like Java or Flash. OpenLayers is built entirely upon open source Javascript libraries, with the vector editor making use of SVG to render the data. Having another opensource editor on the OSM horizon is bound to accelerate the pace of development of the other editors. OpenLayers developer, Chris Schmidt says that he had planned to start working on an OSM editor in the next few weeks. Its going to be great to see what further collaboration between OpenLayers and OSM can bring.

If you want to get hold of raw OSM data to play with, you probably want to get hold of a Plant dump – a weekly snapshot of the OSM database. As the data in OSM grows in size, planet.osm also grows. The last planet.osm was 3.5GB when decompressed – thats a whole load of XML that has to be shipped around the place each week. Jon Burgess has produced a set of tools that produce a diff – a file that contains information about changes to the dataset, so all you have to do is apply the diff to your existing OSM data to have the latest version. Very nice work.

And finally, just when you think you have the whole tagging thing nailed down, something like this happens:

Read more about tagging streets like this one here

By Nick Black

State of the Map 2007 – Conference Update

Preparations for the State of the Map 2007 is in full swing. Head over to for the latest news, including a preview of some of the talks and workshops planned for Manchester in July.

To be kept up to date with the latest announcements, you can subscribe to the State of the Map feed, or email to be added to the mailing list.

This week on the OSM mailing lists

Its been another high-traffic week on the OSM mailing lists, so lets get ready for a whistle-stop tour to the world of OSM.

The legal debate continues, but the focus has shifted to an attempt to aggregate information about Case Law, Statute Law and general legal questions onto the Legal FAQ wiki page. The principal behind this is firstly to gather together information that we can present to a friendly (and perhaps charitable) copyright lawyer and secondly to get information about similar cases. There are a couple of papers that are definitely worth looking at, this one, written by Dr Charlotte Waelde from the AHRC Research Centre for Studies in Intellectual Property and Technology Law at the University of Edinburgh and this page from the Science Commons website. If reading a journal paper is just too much like hard work, Richard has summarised the main points of the paper here. If direct action is more your thing, some OSM users have been declaring their contributions Public Domain on this wiki page.

If you are new to OSM, Geo and OpenSource projects, there’s probably a lot of things that confuse you. If you are wondering what the difference is between GPX and GPS, head over to the glossary page of the wiki. If there’s a term you want defining, just add it without a definition and someone will update it before too long. There’s also a new mailing list for newbies – sign up here and start asking all those questions that have been bugging you.

There’s been a load of development going on in the OSM commuinty this week. Tom Higgy has written a script that will calibrate OSM image tiles letting you use them with the opensource Treck Buddy navigation software. Take a look at Tom’s work on his site. Next up, Mathew has been working on a new rendering engine that takes OSM data and produces a postscript file, an interesting new take on the rendering issue. The pragmitic developer says; “Maybe there is a use for it, maybe not. I just like hacking PostScript, so this seemed a sensible merge of two enjoyable things…”.

The “Applet” is the editing tool that you use when you click on the “Edit” tab on the OSM website. Its been around since the very beginning of OSM, the first version was written by Steve, the next by Tom Carden, the way support was put in by Imi and inbetween that a few other people have had a hack at it. The Yahoo imagery has prompted a fair bit of development work on the applet. Nick Burch put in some fixes a few weeks ago, and this week Dan Moore has made quite a few bug fixes, including enhanced panning and zooming functions – all of which are now on the live site.

Keith Sharp’s been bussy too, adding a script to extract polygons from the weekly planet dump – useful if you want to extract a particular area of data, rather than load the entire dataset. You can grab a copy here.

My personal “app of the week” is Franciso Santos’ fantastic new Yahoo! imagery plugin for JOSM. Download the plugin from here, then fire up JOSM and get ready for some productive mapping. The plugin works by caching image tiles via Firefox and then loading the image into JOSM – get more info here.

Putney Bridge as seen using the JOSM Yahoo! plugin

The tagging discussions have continued this week too. One problem that’s been identified is that there is currently no way to distinguish a tube station from another type of railway station. Currently we tag railway stations with:


Robert “Jamie” Munro’s not happy though, “that’s just wrong”, he says, and he has a point. After all a railway station is not part of the railway, and so shouldn’t be tagged with “key: railway”. One suggestion is to allow multiple tags with the same key, something like:


Whilst this is supported by XML, it is not currently supported by the OSM API. You can follow discussions about tagging and the OSM ontology here. There are a load of new proposed features that you can vote on this week too- take a look at this wiki page and have your say.

As the amount of data in the OSM database grows, and as the uses of OSM data become more sophisticated and diverse, the underlying data structure will become increasingly important. The idea of “superways” is not a new one, but David Earl has brought the matter to light this week, largely in response to mailing list discussions about tagging motorway junctions. David’s proposal is firstly to introduce the idea of a “superway” as a higher level structure on top of the existing ways, as well as encouraging the API and editors to enforce the existing “rules” of ways (they are contiguous, ordered, unidirectional, non-branching sets of segments). David sees several advantages of the proposed scheme; a road in a housing estate that has numerous branches for example, can be grouped as one object, likewise a complex road junction which is not a single node or a roundabout could also be represented as one object.

Basically all we’re trying to do is assign tags to groups of ways without having to do it to each way, or have an easy method of selecting multiple ways – John McKerrell

There are several strands to this debate, but primarily there is the need to represent real-world objects in the OSM database and however this is done it will involve some level of abstraction. Aled Morris makes a good point that the ability of a renderer to render a particular data-model should not affect the development of that data model. The problem is, that the output of renderers will inevitably affect the way people tag objects and the way people perceive the OSM data model. Nigel Magnay makes the point that whilst you could feasibly tag your way around many situations, this is an inefficient way of dealing with the underlying problem, and what we should be doing modeling the fundamentals properly. Of course different people have different ideas of what the “fundamentals” are and what “properly” is. The herding of cats springs to mind, but then this is all part of OSM’s open, community based way of doing things.

Thats all for this week. With all the new development thats been going on there’s plenty of new toys for every kind of mapper to play with – so get out there (or fire up JOSM) and have some fun.

Another week rolls by on the OSM mailing lists…

Oh, my head hurts. I wasn’t around last weekend to do the roundup so Nick agreed to do it. I mailed him suggesting it was a fairly quiet week. “have you been following Legal-talk?” he asked. “Better subscribe. ” I said. Big mistake! It’s not the quantity of mailings that’s the problem, its the passion, quality & general level of understanding. This is where Baz the Blogger’s head really starts to hurt, I’ll keep it brief:

There are three main debates going on at the moment “Is the share-alike road navigable“, “Moving up the stack“, and “The big license debate“. I don’t pretend to do them justice in this one-sentence-per-subject summary so if the subjects interest you and you want to join in, please take a look at the debate. Thanks to David Groom, SteveC, and Tom Chance for starting off these particular threads.

The share-alike road in one sentence is this. Can the license to OSM data be made so that the people that use and enhance OSM data are obliged to make their enhancements available to OSM. To make this concrete, if someone took the OSM data and, for a particular map they placed street names at ‘good’ locations, they would have to return those locations to OSM. There are also other debates on licensing for derivative works. “The big license debate” discusses the pros and cons of CC vs. PD licenses. Should the data be made public domain – a complete free-for-all, or will CC licensing work? One issue with making the data public domain is that everyone that contributed must state that their work is in the public domain. “Moving up the stack” covers whether OSM should just stick to the data layer or move up in some way – afraid this one made my head really hurt!

It is good to see that the FAQ keeps getting updated. For example, people are naturally keen to see the edits and additions they make appear on the slippy map.  Now you keen peeps can now go to the FAQ to find how to get your freshly edited area updated quickly… then clear your cache, have a nice relaxing meal & come back to see the results of your hard labours (on a good day ๐Ÿ™‚ ).

Something weird happened with a question by Franciso Santos posted on “Tagging urban streets” – whats the tagging scheme for roads when you get in the centre of a city. Plenty of discussion to agree the scope of the problem, then Mike Collinson proposed something that seemed to be agreed. Wow! Take a look – it doesn’t happen that often.

It seems to have been a busy week for applications. Or should I say nacient application-lets. OJW announced an atlas generation programme. Richard Fairhust announced a test version of Potlatch, a flash-based editor for OSM data and again OJW let us know about an easy way to generate map jpegs on the fly here, surely these should have a CC license logo on them? Or are they derived works – oh, my head is starting to hurt!

Like most (all?) distributed collaborative projects, OSM is discussed at many levels: on the mailing lists (some that we summarise here, legal, talk, dev, party ) the wiki and IRC. There’s only one thing to say about the IRC channel #osm……  “There be sxpert’s” ๐Ÿ˜‰

Fancy a trip to Spain? Ivรƒยกn (who I’m sure was in rehab) is organising a mapping party in Madrid – why not join in? Oh, and be careful mapping in China.

And finally, you know you’ve got Obsessive Compulsive Open Street Mapping Disorder when “…going to see relatives suddenly sounds interesting…” – too close Dutch! And it just goes on…

By Barry Crabtree