Saturday 20th February 2010

Adventures of an Amateur Cartographer

Every lunch time I go out for a walk of four to five kilometres. Either I get the fresh air or I doze fitfully, head on keyboard, throughout the afternoon. Rather than listen to music for the hour or so of walking I've been in the habit of listening to technical podcasts. I keep an MP3 player dedicated to the backlog of podcasts I subscribe to including Futures in BioTech, BoagWorld, The Java Posse, MacBreak Weekly, Security Now, TWiG, TWiP and Windows Weekly (all of which I wholeheartedly recommend.)

While striding manfully across the streets of suburbia this week I've been listened to some back issues of FLOSS Weekly that I'd previously missed. This excellent podcast by Randal Schwartz covers all aspects of Free Libre Open Source Software, occasionally straying into open source hardware and, in the case of the podcast I was listening to, open source data.

This episode included an interview with Steve Coast of OpenStreetMap.org. Briefly, OpenStreetMap is an attempt to crowd-source the mapping of the whole world so that all the data is available under a Creative Commons licence. While services such as Google Maps are extremely useful, the underlying data is copyrighted and can't be used by third party mapping or navigation apps for iPhone or Android without paying significant licence fees. By collecting IP-free data OpenStreetMap makes free mapping data available to anyone who wants to use it.

Now Google Maps, and my Navman SatNav have a typo in the name of the street in which I live, and so on reaching home I checked the OpenStreetMap site to see if they had got it right. Initially I was disappointed to find that, although my street was on the map, it and a number of other local roads weren't named. And then I realised that this was my opportunity to use my lunchtime walks to make a small contribution to the common effort. The next lunchtime found me setting off with a screen print of OpenStreetMap.org, a pen and a GPS receiver.

The most important rule for updating the OpenStreetMap is that you mustn't copy the data from a commercial source, such as Google Maps or the Ordnance Survey. Instead you must get out there and check the street signs for yourself. Commercial maps contain deliberate errors that can be used to prove when their data has been copied. They can also be slow to update and so may not reflect the latest road topography - for example the Tele Atlas data used by Google doesn't show a local connecting road opened last year - but OpenStreetMap was updated with the new details five months ago.

Editing OpenStreetMap is pretty easy, there are a number of on-line and off-line graphical editors - I've been using the default Potlatch on-line editor which only takes a few minutes to get to grips with. The underlying data is stored as a network of nodes, each representing a junction, amenity or other landmark. A sequence of nodes connect up to form a 'way' which might represent a road, footpath and so on. Both nodes and ways can have a series of attributes stored as name/value pairs that record what they represent, their location, name and a host of other data. For example a local road is tagged with:

    highway = residential
    name = Acacia Avenue
  

As you can see Yahoo! have kindly contributed satellite imagery to make the editing easier. Once you have completed your edits the maps displayed on the website, phones and SatNavs are not updated immediately. You have edited the underlying XML data, but a renderer needs to convert the data into graphical tiles that can be displayed at each of the supported map resolutions. The website supports two of renderers - Mapnik and Osmarender. Mapnik runs on a single machine and is supposed to generate new versions of the graphical tiles every few hours - though every few days has been closer to my experience. The OpenStreetMap database for the whole world is about 61 Gbytes and this has to be rendered into graphical tiles for 18 zoom levels, so this is a lot of processing.

Osmarender is more interesting in that it uses volunteer grid computing to distribute the rendering work across a group of machines on the Internet. It can re-render quicker and there is a neat little trick which allows map editors to mark particular tiles as high priority in the work queue so that they can check the rendering as quickly as possible.

Having updated all the street names hereabouts I got more ambitious and decided to add a new footpath recently built across the local park. To accurately plot the route I used a GPS tracking program on an Android phone. Currently I'm playing with two - My Tracks and GPS Logger. Both can record GPS data at regular intervals as an XML .gpx file on the SD card which can later be uploaded to OpenStreetMap. Once on-line the GPS data can be overlayed onto the map and a way traced over it. I found the whole process simple to carry out and accurate.

At some point during my editing sessions a bug in Potlatch meant that a way I had connected to, but not edited, was duplicated. Only one way was visible in the editor and the rendered map but the name of the street appeared twice. The second way was directly on top of the first. This gave me an excuse to take a look at the underlying XML data - you can select an area of a map and download the data as an XML document. The schema is easy to understand with the data being presented as a series of nodes and then a series of ways connecting those nodes. It was easy to see that the original way data was duplicated in a new way that the XML identified I had created (I deny everything!) This gave me the confidence to go back into the graphical editor and delete the way - the original way immediately reappearing in its place (much to my relief!)

I've really enjoyed my first week's tweaking as an amateur cartographer. It's added a little purpose and variety to my lunchtime walks, but the biggest kick of all has been seeing my updates appearing on the OpenStreetMap website and on the AndNav2 Android SatNav software.

Posted by frogplate at 22:56.

Tags: android, maps, satnav


Wednesday 10th February 2010

Google creates a Buzz

This evening was going to be one of those rare events - an evening off. No computers, no beating IE6 into submission with CSS, just a few episodes of 'The Big Bang Theory' and an early night.

But a few hours ago Google announced Buzz, their third attempt at capturing the Social Networking market. Their previous attempts, Orkut and Google Latitude met with limited success. By integrating this new offering into Gmail they are going straight for the mainstream in a clear challenge to both Twitter and Facebook.

Buzz access is being rolled out to Gmail users over the next few days and at the moment I don't have the new 'Buzz' link under the Inbox in the top left of the page. However I've been able to read and comment on a public Buzz created by another user. Once you have commented to an existing Buzz then any further comments appear in your email Inbox and can be responded to there - as well as from the Buzz pane. This worked fine even without the full account update.

Buzz looks and feels like Twitter but has the realtime update of Google Wave, integrated photo albums, and the mobile version adds location-based features too. For example, the Android Google Maps application updated this evening to add a Buzz layer which provides some of the features of Latitude such as being able search for Buzzes close to your geographical location. Public Buzzes show as small speech bubbles on the map and clicking the Buzz button lists the currently visible Buzzes as a timeline. I can see that someone has just commented from the bus-stop just outside my house!

Unfortunately for full access to the Buzz mobile app you'll currently need an iPhone or Android 2.0+. BlackBerry, Nokia S60 and Windows Mobile are 'coming soon' but it is not looking good for original G1 owners stuck on Android 1.6 who will only have the Maps layer.

Posted by frogplate at 01:22.

Tags: android, buzz, social


Sunday 31st January 2010

NASA Release Aeronautics eBooks

NASA have started to release the history of their aeronautical research as free eBooks. The Kindle, Kindle DX and Sony Readers are the only platforms listed, but the Sony Reader files are simple PDFs which can be comfortably read on virtually any machine. They are working on nook support.

The first book to be released is "X-15: Extending the Frontiers of Flight". The North American X-15 eventually reached 4,500 mph and an altitude of 67 miles (which qualifies as space flight) and this book packs a lot of techie detail, diagrams and photos about how this was achieved into its 644 pages. For example there is a detailed description of the pioneering work in computer-controlled simulators that supported the flight control development and pilot training. Digital computers were not fast enough at that time and so three EAI PACE 231R analogue computers were used.

There is also a lot of fascinating information on the development of the engines, how problems with longevity and vibration were overcome to eventually reach 250,000 Newtons of thrust. It's an excellent read and I look forward to future releases from NASA.

Posted by frogplate at 22:15.

Tags: analogue, ebooks, nasa


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4.0 18-Apr-2012