Giving up twitter for lent

I’ve decided to give up Twitter and IRC for 40 days and 40 nights. This is quite a big deal for me. It remains to be seen how well it works, but I’ve survived the first couple of days. @harry_wood has gone quiet!

Somehow twitter has become very entwined in how I operate. I use it to keep up to date with news and interact with a “professional network” and “friend” type people within various spheres: OpenStreetMap, open data particularly transport data, general IT tech & mobile/web. Reading, interacting, announcing and microblogging on these topics. And it’s great. I’m hooked on it and I’m happy with it, but…

I’m anticipating some possible positive effects of giving it up for the next 40 days and 40 nights.

Maybe I’ll blog more. Somehow twitter uses up a lot of the creative energy that previously would have gone into writing blog posts. I know I’m not the only one to more or less stop blogging as I embraced twitter. There’s a few things I really should have blogged about but lately I’ve just been using my blog for publishing presentation slides. So more to come here hopefully.

These days twitter replaces RSS for many people. It’s normal to tweet with a link to your blog every time you post. Should I allow myself this? I think not. I’m going cold-turkey on this one! Who knows, maybe somebody else might tweet a link to here. Or maybe nobody will read this 🙁   As usual, if you say “hi” in the comments it will make me happy. If you don’t, then I’ll just brood about whether or not I have a signficant number of lurkers.

The other positive effect will be eliminating the time sink that twitter represents. Although twitter is a neat way to distil things and the signal to noise ratio isn’t too bad (otherwise I wouldn’t use it) I can’t deny that it is often just a tempting distraction. One click of that juicey looking tweetdeck icon and I can marvel with a dizzying feeling as technology and society and all manner of fun seredipidous nonsense spins before my eyes, and… oh yes I was supposed to be doing some work.

I’ll be quitting IRC too (Chatrooms for those who don’t know) The mac Adium IRC client lets me auto-join all my favourite OpenStreetMap channels, and then the cute little green duck flaps its wings when someone wants to chat to me. How can I not click on a cute flapping green duck?? I won’t go completely cold turkey on this, because I have some meetings I need to attend, but over lent the duck will die.

I imagine I may move onto facebook and google+ to get my fix of realtime updates. I’ll allow myself this because I see it as another positive. I feel I should try to understand google+ better. After the failure ot orkut, buzz, and wave, it seems google are going to shove this one down our throats via their search results, so perhaps there will be no escaping how important it will be for promoting things. Meanwhile facebook is where all my non-techy friends hang out. I should stay in touch with them better. Also it’s easy to forget that facebook is much more mainstream than twitter, so promoting on facebook has more potential reach, if you can get your message right (and non-techy enough). It can well be argued that twitter is a terrible echo-chambre. A community of people all re-tweeting eachother, stroking eachother’s egos, whilst forgetting that there’s a big world out there beyond. I don’t really think that, twitter friends, but I sometimes wonder.

Well for 40 days and nights I am severing my connection to the hive. Wish me luck!

Oh and if you’re wondering how to reach me, drop me an email. Yeah one of those old things. If you limit it to 140 characters I’ll probably find that comforting in some way.

Society of Cartographers Plymouth

A couple of weeks ago I was in Plymouth for the Society of Cartographers Annual Conference. Lots of interesting talks and a fun and friendly atmosphere, particularly during the evening entertainment: pub quiz, boat trip and rum cocktails. [update: forgot to say my photos from the conference are here]

I came across a strange new breed of people who knew all about making maps using only adobe illustrator. That’s a side of “cartography” which rarely surfaces at the geo events I’ve been to before (and I’ve been to quite a few now), but this seems like a rather interesting artistic end of a map-making spectrum. I didn’t come across anyone who had tried out OpenStreetMaps options for exporting to Illustrator. This probably needs to be made easier, but I suspect Maperative might be a kick ass tool in this arena. I don’t have illustrator myself, so I’d be interested to know how well it works.

I gave a talk on a blend of topics to do with transport and open data and some of my experience of mobile geo development. I talked through some stuff I’ve been working on at The UK Travel Options iPhone app, and the more recent mobile website. Then I gave a few more nice bits of bus route related technology (and cartography) coming out of OpenStreetMap.

The slides and notes (approximately what I said in the talk) are included with the presentation on slideshare, or OpenOffice download, or PowerPoint download …or here it all is in good old pictures & text:

Slide 0

I’ve got four different things I want to talk about.

I want to talk about Open Data, and specifically Open Transport Data. And I want to talk about the work I’ve been doing at, and finally my hobby and passion OpenStreetMap.

Lots to cover, but fortunately they’re all wonderfully interrelated, so it’s really just one big topic.

Continue reading “Society of Cartographers Plymouth”

VisionOn.TV OpenStreetMap interview

As well as giving a talk at OpenTech, I also did little interview about OpenStreetMap for VisionOn.TV:


It’s on youtube.

The “Documentation” link I mentioned is Find out all about the OpenStreetMap project there.

The video featured here is an animation of OpenStreetMap edits back in 2008 (It’s stunning. Watch it full-res for the best effect) There’s even more worldwide editing activity on OpenStreetMap these days.

The talk I gave at OpenTech earlier in the day, is described in the previous blog post (also available as a video) That was going into more depth particularly for developers interested in using OpenStreetMap


Thanks to the nice folk at for organising an interview in their “pop-up studio” there. VisionOn.TV is a pretty interesting citizen journalism project. Their approach was to do almost all their editing (e.g. dropping in the OSM animation video) “live” as they recorded the interview. This probably gives them a more fun live TV feel to their “studio” activities, but it also seems like a clever approach to avoid endless faffing with editing

…which is a big problem with creating video. I spent hours and hours on this tutorial video. The results were not really worth the time it took (That tutorial is now out-of-date for several reasons too) At the time I realised that I could have achieved almost as good a video by practising a few times and then recording the whole screencast in one take, rather than doing things piece by piece and editing clips together, which just takes forever.

I’m interested in this stuff because video is the way to reach out to the masses. Make stuff which appeals to the short attention span of the youtube generation. The Video approach is a no-brainer. The process of making video is difficult. For OpenStreetMap we need better promotional videos and video tutorials. Compare videos on that list, with the “guided tour” video (well flash animation actually) which is front and centre on . It’s a slick persuasive pitch to ordinary non-technical people (Important note: Don’t be persuaded! is one of several companies who get people to contribute geo-data, and then hoard it for their own commercial benefit. You should be supporting the not-for-profit OpenStreetMap project instead!)

This interview video is not a slick pitch. I’m concentrating on trying to explain OpenStreetMap in a persuasive way, and as a result I’m furrowing my brow and looking too serious. And when I first watched it back I thought I’d really failed to get various important messages across, particularly about the open data aspects of OpenStreetMap. But I guess that’s the short video way. Dumb things down and miss out the details. I feel better about it when I see a facebook comment from my (non-techie) sister saying “good explanation, I get it now!”.

OpenStreetMap at OpenTech 2011

I gave a talk at OpenTech 2011 yesterday. This is a big open source open data London technology conference. A lot of fun.

I gave an overview of the developer ecosystem around OpenStreetMap data, how web and mobile app developers can use OpenStreetMap, and how the OpenStreetMap tile server is only a small part of that. This included a whole sequence of shiny new slides to illustrate these points by gradually building up a nice diagram.

Watch the talk video on youtube

Slides on

The session listing on lanyrd has some photos etc linked from there.

The following is the slides in a form which is less likely to crash your browser, along with notes


Open Technology enthusiasts will have heard of OpenStreetMap before


If you’ve only taken a quick look, you’ll perhaps have the idea that OpenStreetMap is an open source competitor to Google maps. It kind of is that, but that’s not really the whole story.


It’s more accurate to compare OpenStreetMap with wikipedia. It is very much the wikipedia of maps. Similar for a number of reasons….

Continue reading “OpenStreetMap at OpenTech 2011”

London Silicon Roundabout meet-up

I went along to a “London Silicon Roundabout meet-up” last week. It’s a very dragons den style business pitching sort of event, both in the presentations later on, and in the kind of conversations people were having while socialising beforehand. I did my best to describe to a few people, but I shall have to polish my pitch a little. The various projects we have on the go at the moment, make for a rather confusing story. I probably should’ve stuck to describing our iPhone app ‘UK TravelOptions’.

After the socialising with beers on the roof terrace, there was a more formal sit-down presentation session. I think the presenters were told they had five minutes and then given 15/20 minutes. ~100 people in the audience. Some were real investors. Many, like me, were just enjoying playing the role, imagining ourselves to be investors. Lots of chin scratching and awkward questions being asked. These were the presentations and some of my thoughts on them: – User generated news site a.k.a. citizen journalism. Well presented. They have algorithms for deciding if content is unconfirmed vs credible (which he over-egged the sophistication of). Also rating mood of an article on a percentage level. This idea reminded me a lot of (ancient history). But I mainly found it interesting that they’d gone for localised city-based news sites. He didn’t really explain why. – iPhone app for meeting up with friends. Meetings are auto-arranged matching by location (a geo app!) and also by your free time calendar. They’re building their own more exclusive friends network. Just your close friends, rather than hooking into twitter and facebook networks. It was a slick presentation, but it’s doomed to fail. There’s a huge critical mass challenge with that idea, worse, a “geo-critical-mass” challenge. This has killed many other “find friends nearby” app ideas which have gone before it. – I wanted this to be a good pitch. The idea is obvious from the name, and it’s a good one. As a student I was bristling with untapped computer programming enthusiasm, and a need to earn some peanuts, but no obvious gateway into casual part-time skilled job. Companies (as far as I could tell at the time) were only looking for full time graduates. And yet since then I’ve come across countless situations where I’ve thought “surely we could hire a student to do this fun bit of website coding”. Sadly the pitch scored a big FAIL because he didn’t show the actual website! Also his claim of quality (of freelancers) was not backed up with a convincing explanation. – eductional mobile app. Presenting educational content and testing interfaces within a mobile app, but also a platform for creation of content. It was clear they’d engaged with school teachers and academics, and figured out clever ways of letting them, or persuading them, to do simple content authoring for mobile screens. This was my favourite talk. Education is a fun software genre. Mobile education is going to be big. I wonder if john mckerrel’s examtutor apps were one of the competitors they’d checked out. I’m sure my android app will be if I ever release it 🙂

Tag Bento – tagging of objects in photos. Didn’t really understand the idea of this one. Photos of products. e.g. make-up bag spread out on a table. These were ‘tagged’ with linkified areas of the photos taking you to sites for purchasing them. Users could create these object tagged product photos, but it wasn’t clear why.

“I’ll tell you where I am… I’m out”

Bus route rendering at RewiredState

I made a bus map.

bus map

Not just an image, but a dynamic “slippy map” rendered at several zoom levels.

This was my “hack” for the RewiredState, National Hack the Government Day”, a gathering of hackers who build something in a day, with the aim of tackling government/society problems, working with government data. Projects are presented at the end of the day.

I created the bus map by “rendering” OpenStreetMap data. By this I mean starting from raw map data, the underlying vector data, the coordinates and connections of every road etc, and creating raster images arranged in tiles at several zoom levels, for the map display linked above.

Clearly within the graphics routines this bright red routes data is drawn in a particular order, and in a sense it is laid on top of the map, but it’s important to realise the routes are baked into the raster images. This isn’t a javascript overlay. Rendering data in this way has advantages and disadvantages over javascript overlays. An advantage is that we can show all the bus routes of London when zoomed out, without crashing the browser. Other advantages are in the subtleties of how you can make the map look. I haven’t really demonstrated this very well here yet, but I hope to make some improvements. If you look closely some tube station labels are drawn over the routes, which at least shows it’s not an overlay. There are other (better) OpenStreetMap rendering examples elsewhere

bus map close-up

Getting the data

You can download raw OpenStreetMap vector data for the entire planet. In fact I took an england extract in PBF format offered up by geofabrik. From this I just chopped out the London area (this bounding box) using the tool “osmosis” with this command:


$OSMOSIS_HOME/bin/osmosis \
   --read-pbf ./england.osm.pbf \
   --bounding-box left=-0.543 right=0.337 top=51.719 bottom=51.253 idTrackerType=BitSet \
   --write-xml ./london.osm

Once I had london.osm, it was time to put this through the Mapnik rendering tool. Very broadly the steps were:

  • Install Mapnik. In fact this is several steps, but happily I already had it installed. The ‘Build your own OpenStreetMap Server’ tutorial by Richard Weait was useful for this
  • Load the data into postGIS with a command such as ./osm2pgsql -S --slim -d gis ./london.osm
  • Edited ‘’ to render a single image in central london as a test
  • Edit ‘’ to specify the london bounding box and zoom levels. Initially I’ve rendered zoom levels 7 to 15.
  • Run ‘’ to create the tileset (png files in a directory structure)
  • Made a HTML file with the javascript to launch OpenLayers fullscreen pointing at these tiles (do ‘view source’ on the site to see the javascript for this)
  • Copied the stylesheet file ‘inc/’ to make a new style layer for bus route relations (thanks to SK53 for suggesting this)
  • Reference the new layer in osm.xml, and ‘inc/’
  • Test using ‘’ before re-running ‘’ to re-render the tiles.
  • Added more rules for varying thicknesses and a TextSymbolizer for showing route labels

My busmap stylesheet so far: style.tar.gz


Among the list of rendering examples linked above, is the one called “ö” which shows bus routes throughout europe. In fact this is one of the best examples of customised OpenStreetMap rendering. Really nice colour and style choices with subdued colours for the background features enhancing the bold transport lines very clearly. So bus route rendering has certainly already been done. What’s the point in my map then?

öpnvkarte is very german. It’s named after a german transport network. The map is quite literally centred on Germany, and you’ll have noticed it has an un-typeable german character in it’s URL (although Shaun has provided as a more sensibly named proxy). Petty irritations perhaps. So what else?

As far as I’m aware öpnvkarte hasn’t been updated in a while, so by re-rendering today’s openstreetmap data, we can see how the community has progressed with adding more routes. I was slightly disappointed to find that there wasn’t much difference in London actually. Just one or two details. Compare here with here. But OpenStreetMap people tend to be motivated a lot by renderings and other uses of the data they’re gathering. If the bus map stops being updated, then people stop adding bus routes.

There are other things which are less than perfect about öpnvkarte. It’s not a worldwide rendered tileset. It went worldwide for a few weeks but the server didn’t manage to cope. (I know my map is obviously not competing very well. I just rendered tiles for London!)

Wordwide tile rendering and re-rendering of updates, are tricky technical challenges. Obviously the developer of öpnvkarte is under no obligation to do these things, it’s just a shame that he doesn’t. More of a shame is that he doesn’t (as far as I’m aware) share his stylesheet config files. Again he’s not obliged to do so, and given the amount of work he must have put into it, perhaps it’s understandable. But sharing stylesheets would allow people with hardware and tuning know-how to have a go at tackling these other hosting challenges.

So those are a few weak justifications for starting all over again and attempting to build a different bus map stylesheet. My mapnik config files are hopelessly rudimentary so far, but it’s a start. Mostly though, this is just another baby step in my slow climb up the Mapnik learning curve. I wrote a diary entries back in January about this, but until this weekend I hadn’t tried anything further.

It was good to get up and present this rendering idea at rewiredstate, to a bunch of hackers and data mashers who I think would find this sort of thing interesting to play with themselves. I know a lot of them will reach for the boring old google maps toolsets for their map mashing work, but hopefully I gave a hint at some of the raw power and rendering fun offered by OpenStreetMap. Perhaps I should have made this important point again though: You can just use the familiar google maps javascript API on top of OpenStreetMap basemaps!.

The important point I did remember to make in my 2 minute slot: Next weekend we’re having a London OpenStreetMap hack weekend. I must try to prepare this time!

Thanks to the hard working RewiredState organisers and their sponsors (wired uk, tso, dxw) for a great day, and for all the free penguin biscuits and beers in the pub afterwards.

UPDATE: New transport map from Andy Allan. My friend Andy is creator of OpenCycleMap and all round Mapnikmeister. Unveiled today (14th April), his transport map is auto-updated and rendered worldwide (how are your local buses looking?) with beautiful pale shaded background cartographic choices. I think we can safely say I’ve been outdone on this one 🙂

placr tube-radar

placr Tube Radar on an iPhoneHere’s something I’ve been working on at placr:

>>>> <<<

[ is a bit different these days, but the tube stuff is actually available at ]

Have a play with it. The site is designed to work well on mobile screens. You can get to it by typing ““. [update: These days that’s also something different. Sorry for the confusion]

The red and blue lines indicate tube performance in terms of “headway”. The time between trains. Closer to the centre means shorter headway (good!) further from the centre means… waiting around a while.


placr Tube Radar at London Bridge

You can compare the data over the past 24 hours (red) with the “normal” levels (blue) which are averaged over a longer time period, but at the same platform and same time of day. Hopefully this will give an indication of how good or bad or erratic your service is likely to be today.

If you’ve chatted to me about what I’ve been doing at placr, you’ll have noticed I’m fairly hopeless at describing it. So hopefully this will give you a better idea, although this is only part of part of what I’ve been doing. We decided it was time to bring some stuff to the public-facing surface from one of our projects. We’ve spent a while gathering and analysing performance metrics of the tube, and this is one kind of output we’re seeing. To get this out in time for the tube strike was a bit of a last-minute rush, so it may look rough around some of the edges, but here’s hoping some people will find it useful (or at least interesting) over the period of the tube strike.

Talks and thoughts on OpenStreetMap mapping parties

(photo Copyright All rights reserved by SINFOGEO)
A few weeks ago we had a big OpenStreetMap conference, the annual “State Of The Map”. This year it was in sun-baked Girona. “State Of The Map 2010 felt like a coming together of all my OpenStreetMap friends from around the world” Read my more detailed write up over on my user diary. There was a diverse variety of talk topics, from OpenStreetMap technical nitty-gritty, to big business GIS uses, to worldwide travels and humanitarian mapping. The full list of sessions is here. My talk this year was part of the “community track”.

Party Time! Good and bad ways to run OpenStreetMap mapping parties

UPDATE: Video of the talk is now available

I seem to have become the chief event organiser for OpenStreetMap in London, not because people massively admire the way I do it, but because it’s actually fair amount of effort, and I’m the one who got suckered into doing it. So this talk was mostly about my experiences of running these regular “mapping party” events, which we do every two weeks as a “mapping party marathon” (Sounds interesting? Check out when the next one is!)As I stressed in my talk, my approach is not ideal. There’s lots of things I don’t get around to doing. In particular I haven’t really tried to drum up press coverage of events. For one reason or another we never have very much luck at attracting new poeple. Although we try to be welcoming to new faces, it mostly ends up being a fun social meet-up where people know eachother. In the questions I was asked “what are my ideas for attracting new people?” to which I gave a hand-waivey response, but the truth is I don’t really know.

So I thought it counterpoised my talk quite nicely when Thea Clay got up and talked about outreach to non-technical communities and spoke about some of the successes she has had reaching out to local community groups and attracting new people to mapping parties in the U.S. This seems like a direction we need to go in, and I hope to find time to try this more in London. But then again…

Ultimately I think the most important message she had, was that OpenStreetMap is too difficult for non-techy people. They get the idea of creating open maps. They enjoy the outdoor aspect of data gathering, and they will have a lot of fun when you first take them out to do this, but the minute they sit down and take a look at our map editing tools “you can see the look on their faces change”.

Perhaps then the most important role of OpenStreetMap events, is to foster the existing OpenStreetMap community in an area. I would even go as far as saying that most outreach work at the moment should target boring old techy people and developers.

This is not the end game. We absolutely want to attract young people and old people, mothers and grandmothers, but getting techy people excited about OpenStreetMap is easier and actually far more effective than anything else at this stage. They’ll learn the tools quicker. But more importantly, these are the people who will go out and embed OpenStreetMap in their websites, taking it to new audiences, or if we’re really lucky they’ll go on to help solve the technical problems of OpenStreetMap and make the next useabilitiy break-throughs.

Obviously any publicity is good publicity. Any mapping party is a good mapping party, but I’m trying to consider where effort is best spent. Are we getting ahead of ourselves to try to engage with local community groups? Maybe I’m just working the geek angle, because that’s what I know best. As I said in my talk, press is important, and press (or PR?) is something OpenStreetMap needs to get better at.

Ruby code for converting to UK Ordnance Survey coordinate systems from WGS84?

Ruby code for converting to UK Ordnance Survey coordinate systems from WGS84? It’s one of those things I’d assumed would be a five minute search -> cut-n-paste job. But no. Well now you can cut & paste from here.

Using Proj4 and the proj4rb bindings

You can do all manner of coordinate projecting using Proj, and this is available within ruby code via proj4rb. To get set-up, install proj. On ubuntu you can do:

sudo apt-get install proj

download the proj4rb gem file (the ruby bindings), and install the gem:

sudo gem install proj4rb-0.3.1.gem

To use in a plain ruby script:

require 'rubygems'

require 'proj4'

To use in a rails app, add a line to your environment.rb file

config.gem "proj4rb", :lib => "proj4"

Probably all obvious to any pro-rubyist, but I got stuck at various stages of that. Anyway once you’re set up…

This code will do a conversion from WGS84 lat/lon to eastings and northings:

lon = -0.10322
lat = 51.52237

srcPoint = * lon.to_f / 180,
                            Math::PI * lat.to_f / 180)

srcPrj  ="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs")
destPrj ="+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 "+
                                      "+ellps=airy +datum=OSGB36 +units=m +no_defs")

point = srcPrj.transform(destPrj, srcPoint)

puts "" + lat.to_s + "&mlon=" + lon.to_s + "&zoom=16"
puts "Converts to:";
puts "" + point.x.round.to_s + "_" + point.y.round.to_s + "_106"

Originally I was trying just the ‘destPrj’ string, and calling the ‘forward’ method, but this seemed to be skipping the datum conversion, resulting in everything being 100m out. It seemed to be necessary to use the ‘srcPrj’ string and the ‘transform’ method, to get the datum conversion happening.

You can look up the mystical proj strings on

(UPDATE)  If you’re interested in converting in the other direction, using the proj4 gem, see Peter Hicks blog: Converting OSGB36 (Eastings/Northings) to WGS84 (Longitude/Latitude) in Ruby

A pure ruby implementation

Like many naive developers who have gone before me, I started out thinking that these coordinate transformations should be acheivable with a few simple formulea, and was expecting to be able to copy & paste a block of ruby code from somewhere to do it without installing any gems.

I didn’t find any such code, but frustration with proj problems (before I got that working) led me to create a pure ruby solution, by porting this pure javascript code by Chris Veness into ruby. So there we go:

osgbconvert.rb – Conversion to Ordnance Survey coordinates in pure ruby

You can run it to see an example conversion with the output:

wgs84 lat:51.52237, wgs84 lon:-0.10322
Converts to:osgb36 lat:51.5218609279112, osgb36 lon:-0.101610123646581

Converts to:easting:531691, northing:182090  As a grid ref:TQ31698209

This includes ported code for Convert co-ordinates between WGS-84 and OSGB36 and ported code in one direction for OS Latitude/Longitude to OS National Grid (coordianate systems explained below) Also I haven’t faithfully stuck to what Chris’ functions return.

There is a bunch of maths, but it was quite a straightforward syntax conversion, and it comes in at about 150 lines of code. Somebody should do this for other languages. I’m sure other languages offer more beefy libraries equivalent to proj4. The main benefit of this is for quick copy & paste coding.

Mind you, if you are copying and pasting this, be sure to worry about the fact that it is LGPL licensed by Chris Veness [Update: It’s now shown under the more permissive CC-BY license on his website. Take your pick!]  For my part, you can credit me too if you like, but I don’t care.

I also came across another implementation, license unknown.

About Ordnance Survery coordinate systems

Chris Veness’s page is well linked because the code comes with a comprehensive description of what’s going on. However I misunderstood a few things even after reading it several times. Here’s my noddy guide to Ordnance Survey coordinate systems:

WGS84 is what I would call the “normal” latitude and longitude coordinate system. These days web developers passing around latitude and longitude values are normally using this. It’s what OpenStreetMap works with if you want to point to a location with a URL such as : (the office).

Ordnance Survey OSGB36 – Involves coordinates which are also called “latitude and longitude”. The numbers look very similar, and in fact if you get them confused and use one in place of the other, you’re generally only ~100 metres off. At this point I could mention “datums” and “ellipsoids”, but who cares? How do we fix it? With the above ruby code, use the function convertWGS84toOSGB36 (or convertWGS84toOSGB36 in the other direction)

Couple of formatting things to note: Both WGS84 and OSGB36 latitude & longitude values can be expressed in degrees and minutes rather than decimal, and with N S E W letters on the end. For example 51°31′20.53″N 000°06′11.60″W If longitude has a W on the end it would more “normally” be a negative number. The letters on the end do not make this an “Eastings/Northings” coordinate. That’s a different system…

Ordnance Survey National Grid Reference Eastings and Northings look totally different. For the placr office the easting is 531691. The northing is 182089. On these numbers the first digit is special. It’s identifying which “grid” square we are in, counting from zero. Everything in London is in grid square 5,1

National Grid References with letters are the older more human friendly version of that. So “TQ 3169 8208” is the equivalent. The 5 and 1 are removed, and instead we represent the grid square separately at the front. Everything in London is in grid square “TQ”. Just to munge things together a bit more, we might drop one digit of precision and drop the spaces to give “TQ316820”.

Don’t ask me how Landranger sheet numbers fit in. I’m going back to my WGS84 thankyou very much.

Paul Downey and London Wiki Wednesdays

Last Wednesday was London wiki wednesday again. We struggled a bit with organisation this time. The usual to’ing-and-fro’ing around finding sponsors and hosts was confounded by a problem with the website. SocialText foolishly switched it to be hidden from… well the web… which really doesn’t help when you’re trying to promote an event. Despite these difficulties, enough people came together at NYK to make for a decent gathering, with some interesting presentations. Actually the low attendance makes for some nice face-to-face group discussions.

For me the highlight was chatting with Paul Downey. I’ve run into him once or twice before, and was familiar with tiddlywiki, which he presented again. This is a somewhat wacky animated javascripty tool which is quite different in it’s interface and behaviour compared to “normal” wikis. Surely the work of an evil genius…

But it turns out Paul Downey is also responsible for this remarkable creation:

see it bigger to read the funny labels. Also with annotations on flickr.

A fascinating cartoony metaphorically abstracted representation of web technologies. I came across this a couple of years ago, while I was still an integration consultant, and I found the “SOA tower of babel” particularly amusing (and accurate)