LBi London

Lost in conversion

Posted by Jim MacAulay February 4th, 2011

It is probably accurate to claim that the United Kingdom is the most precisely mapped country on Earth. This is down primarily to the Ordnance Survey agency, who in the late 1700s took on the task of mapping the Scottish highlands in order for the English gentry to hunt down and shoot the locals.

Since then those Ordnance Survey chaps have constantly travelled the land with nothing more than a few brass measurement tools, pencils, paper and a hard hat (in later years due to health and safety). The dedication and accuracy attained by this group of OCD savants was such that years later with satellite imagery and GPS the UK is still the envy of the world for its renowned OS maps. Even the USA (which calls itself civilised) does not have maps which detail every contour line and public house in the land.

Now as part of their tasks the OS surveyors also accurately mapped every postcode in Britain. For a while this information was sold by the Ordnance Survey but since our government has become ‘open’ they mandated that this information should be in the public domain; which is a good thing since it was our tax which paid for its collection in the first place.

The ubiquitous GPS systems have recently turned us into a nation of location based obsessives. As such, organisations now want to plot all their branches, outlets and cash machines on the map. To do this you need to “geocode” the postcode of their address to get  latitude and longitude values then they can be easily plotted. The philanthropic organisation Google has developed a very nice API which allows you to do exactly this, although Google’s generosity ends at 2500 geocodes per day where upon they’ll ask you to part with some cash. But we in Great Britain have no need of such a service since the Ordnance Survey produce a file free for us to download which contains every UK postcode together with their grid reference, all 1.7 million of them.

This is exactly what I thought when I needed to encode thousands of locations. The problem is that the OS craftsmen used a grid system based on coordinates expressed as beautiful 6 digit integers. Brash modern GPS and mapping websites use the hideous longitude and latitude system expressed as ugly irrational numbers. It turns out that converting between the two systems is not as simple as multiplying by 2.54 or multiplying by 9 dividing by 5 and subtracting 32; the whole process is far more complex. Luckily those very clever people at the OS realised this so they got out their slide rules and worked out how to do the conversion, then they shared it with us:

So after I coded this up* I found that the coordinates were inaccurate by 100 meters or so. After a bit more reading I discover that the OS boffins used a different ellipsoidal model to that of the GPS systems, basically they consider the earth to be a different shape, but both systems are still correct !?!? Now, I know what you’re thinking; why don’t you simply use a Helmert Transform! I had came to the same conclusion and this is exactly what I did :

Having now coded this up* I set about converting all the UK postcodes from the elegant OS Grid coordinates to the loathsome decimal coordinates of Google maps. Doing all those calculations for each of the 1.7 million postcodes was going to take considerable time so I set it off and decided to make some tea. Imagine my surprise when my laptop announced it has completed the task a mere 35 seconds later !!

So now I have all the British postcodes and their locations in the correct format and they seem to be very accurate indeed. I’ve also written a service which loads all this data into memory as a hashtable and will convert either individual postcodes or a file of postcodes that a user supplies. The service will be available for us all to use in the near future. I’m afraid however that Johnny Foreigner will still need to cough up his euros/dollars/rubles etc to get Google to geocode his local postcodes as the OS team were afraid of sailing and so didn’t get around to mapping the rest of the planet.

*When I say ‘I’ coded I am speaking figuratively.

Tags: Convertion, Geocode, google maps, Mapping, Ordnance Survey

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Weekly Social Media Update

Posted by Sinead Doyle September 1st, 2010

Gmail Voice Calls

Calling from Gmail

Google has added Skype-like functionality to Gmail: you can call landlines and mobiles from Google Chat, for free. It’s currently available only in the US and Australia, but keep your eyes peeled for the UK launch: the service has already proved popular, with over a million calls made in the first day.

Diaspora Launch

If you’re tired of Facebook’s increasing ubiquity, you have only weeks to wait before you can jump ship: Diaspora will launch its consumer facing alpha version in October. The open source code will be released on the 15th of September, giving developers a headstart to think about how the project can be integrated with existing services.

Interactive Twitter Murals

The Canadian Tourism Commission has placed giant touch screen murals on US high streets to display real time updates from people talking about Canada. What better way to inspire the persuadable passer by? Hat tip to Pipa for finding this.

Arcade Fire Streetview Video

This is really rather lovely. Arcade Fire are seamlessly integrating Google Street View images in their latest music video – “The Wilderness Downtown”. Simply enter your childhood postcode, and watch as the video is populated with your own nostalgic landscapes. Clever use of HTML5 – thanks to @blackplastic and @samstokes for spotting it.

David’s Bee Beard

Save the bees! LBi and Your Mum have teamed up to draw attention to the plight of the humble bee. Tweet your support to David’s Bee Beard and watch as the beardy petition becomes a mighty swarm.

Tags: Arcade Fire, bee beard, Canadian Tourism, David Cameron, David’s Bee Beard, Diaspora, Facebook, gmail, Gmail calls, Google calls, Google chat, google maps, interactive murals, LBi, music video, save the bees, Skype, Social Media, street view, twitter, twitter murals, voice calls, Wilderness Downtown

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Weekly Social Media Update

Posted by Sinead Doyle June 28th, 2010

LinkedIn Revamps Groups

LinkedIn has revealed changes that make its groups more like Facebook and Twitter, with a new emphasis on starting conversations. Users can “like” comments or conversations, and “follow” organisations or individuals. It’ll be interesting to see if this boosts interaction, or just further complicates the user experience.

Google Maps for Android Copies Foursquare

The new Google Maps 4.3 for Android has added a location sharing feature. Add a friend to your Google Latitude friend list, and you can share location updates. Does this mean Google Latitude might finally be useful?

Barclays Virtual Reality Game

Barclays is reaching out to a younger market, with the release of a new virtual reality game in which players earn points by using money wisely. 56 Sage Street will be promoted with a Facebook page, where players can share tips on the game.

“The Social Network” – the Facebook Film

The poster for the upcoming Facebook film “The Social Network” has been doing the rounds for a few weeks, but now there’s a trailer to go with it. I would embed the video from YouTube, but apparently Sony pictures have “blocked it on copyright grounds”, and the share function on their own trailer site doesn’t seem to work. Sigh.

David on Demand

In case you missed it, David on Demand was one of the best things at Cannes this year. Take a look.

Tags: 56 Sage Street, Android, Barclays, David on Demand, Facebook, Facebook Film, follow, foursquare, Google Latitude, google maps, like, linkedin, The Social Network, twitter, Virtual Reality

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