John Snow: The Myth of the Map

John Snow destroys the Pump handle

I have admired Jon Snow’s map of the 1854 Broad Street Cholera Epidemic since the first time I saw it, flicked up on a presentation about the power of GIS and described as the beginnings of spatial data techniques:

“John Snow mapped the Cholera deaths, and used the map as an argument to have the Handle removed, so stopping the epidemic. He is the father of modern GIS spatial analysis!”

It’s an oft repeated tale that resonates with us , a scientist as hero, the mapmaker as saviour.

With the recent bicentenary, Jon Snow’s map of cholera has been celebrated widely anew, with new exhibitions and even a GIS data package from a Southampton University postgraduate researcher, displayed to great effect by the Guardian.

It’s a great advert for GIS, or Spatial IT.  So much so that some spatial professionals groan when it pops up in a presentation, even playing ‘Snow Map bingo’ over Twitter.

The trouble is that this is all a myth.

Snow apparently drew the map months after the outbreak. I’d seen this stated as fact before, but in the wealth of publicity telling me otherwise decided to re-investigate.

I decided to actually read John Snows book, On the Mode of Communication of Cholera. (Available as an ebook from Google)

I began to seriously doubt he would have had the time to produce his famous spot map from becoming involved to getting the pump closed.

He becomes involved on September the 3rd,  after the horror of 70 depths on the 1st  and 127 by the 2nd.  The local inhabitants are fleeing the scene, Snow arrives and examines the water from the local Pumps, already suspecting contamination of the Broad Street pump.

He examines the Broad Street Pump water and having found:

“so little impurity in it of an organic nature, I hesitated to come to a conclusion” 

He appears to discout the pump as the root cause.Then on the 5th, he re-examines water collected over 2 days from the Broad Street Pump and discovers:

“an amount of organic impurity, visible to the naked eye”

By the 6th he requests permission to gather a list of the deaths of Cholera from the week ending 2nd September, tabulates this to conclude the outbreak began on the Thursday and then concentrates on gathering as much information as he can for the 83 deaths registered for the last 3 days of the week

He does this by physically returning to the Broad Street pump, and interviewing people :

“On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the pump”

By the evening of the 7th, he has had an interview with the board of Guardians of St, James parish.

“ In consequence of what I said, the handle of the pump was removed on the following day.”

He never mentions mapping the locations at this stage, In fact, it’s rather more a frantic dash around the Streets of London, interviewing surviving relatives  shopkeepers, cafe owners etc, all based on his textual research. He’s aware of the spatial link, but he doesn’t need a physical map to display it.

In fact he  gathers information that would have been unobtainable from just looking at the locations of deaths on a map, finding spatial links in the day to day narratives of people at work, drinking from infected water supplies and returning home to die, or having water brought from Broad Street to their new homes miles away.

John Snow is no less the hero, he just used different tools to get the pump closed.

Snow first presented a Cholera Spot Map at a meeting of the Epidemiological Society of London on Dec 4, 1854.  Probably because, then, as now, it immediately leads the viewer to decide the pump must have been responsible.

Not convinced?  Still want to believe?

Then check out this 2000 Lancet article, Map-Making and Myth-making in Broad Street: The London Cholera Epidemic, 1854

The authors detail the evidence, including maps that actually predate Snow’s, by Edmund Cooper, an engineer for the Metropolitan Commission of Sewers, drafted to counter claims that the sewers were to blame for the out break.

More, the authors’ warn of the possibility of GIS to mislead and seduce, stating:

“If the methodological assumptions underlying these uses of GIS are correct, Edmund Cooper and not John Snow would have been credited with unravelling the Broad Street cholera outbreak”

Furthermore, a cartographer’s study of the  modern reworkings of John Snow’s map, Tom Koch’s 2004 paper provides sobering reading:

“…dangers occur when professional cartographers and geographers attempt to map data from fields in which they are ignorant”

The following words from his conclusion, echo my view.  That Maps aren’t a depiction of reality, they are powerful memes that deliver their desired message to viewers.

“…map-making is mired in the myths and assumptions of the individuals who promote this or that map within the culture(s) the map-makers serve.”

Perhaps now is the time to finally stop promoting the myth of John Snow’s map within Spatial IT.


28(+2) Days Later

One month in at Southampton University, and I’m enjoying the work immensely. I’ve produced maps and figures for colleagues, learnt and passed on “Geo-wisdom” and even turned down a talking head spot on Radio 5 Live talking about the Undiscovery of Sandy Island. Must book that Media Training course…

My colleague Richard Treves, (his blog is over at Google Earth Design) stepped up to plate and did a great interview.


He mentioned that users of maps especially Electronic versions, tend to trust and follow them as true representations of the physical world.

In fact (as every Cartographer knows) Maps are more complex beasts, effectively transmitting who ever designed the map’s version of reality. They’re the original “Geomeme”

I guess Sandy Island proved that the phrase “Here be Dragons” still has a use cartographically today.

Connecting the dots…

Connecting the Dots

I will be leaving Bournemouth University in early October, to take up the post of Senior GIS Cartographer at the Cartographic Unit of Southampton University in November.

It is an amazing opportunity, and I’m really excited about the chance to do more of what I love, creating maps and images, supporting academic colleagues’ research and keep engaging with new technologies and techniques to push spatial information “out there”.

Over the last 8 years Bournemouth University has supported my career, acted on my ideas and I was privileged to work with some amazing colleagues.

I’m most proud of three things from my time at BU:

  1. Google Seeing Beneath Stonehenge: A great example of a team project that provided innovative ways for the public to engage with archaeological research.
  2. Bournemouth Archaeology: I set this up with a colleague in 2005. I haven’t been directly involved for the last few years, but it’s gone from strength to strength.
  3. BUGIS Consultancy: Setting up another outside facing consultancy has provided valuable experience in the highs and lows of working as an intrapeneur in a large HE institution. In particular, creating and running the GIS for Environmental Managers CPD short course was probably one of the most rewarding work experiences I’ve had.

My time at Bournemouth University is only memorable thanks to all the staff and students who I have worked with over the years; I am grateful for all their support, help and encouragement and I wish everyone the best for the future.

Seeing beneath Stonehenge: Data Mining Under-The-Earth?

With the successively launch of the KMZ, knowing that the data is “free”, being used and hopefully enjoyed in Google Earth has made me reminisce about my time on the Project ,and the last few weeks before launch as I worked feverishly editing KML code, checking Sketchup model imports and re-positioning Gigapan panoramas so they hugged the ground again.

What stays with me is how easy it was to bring in anything we had created using the Google suite of products. Sometimes there were glitches, but there was always a forum or blog post. Someone who’d encountered the bug, solved it, or had a workaround we could adapt and use. We rarely had to turn to our Google Liaison.

Most of our problems came from exporting GIS layers into Google Earth, and only then because of the difficulties of changing Map Projections. The normal tools for this work well, but we needed our British Grid data to map exactly into the Google globe “real location”, rather than within a few meters. We had resigned ourselves to a complicated series of imports, map proofing and educated adjustments.

Luckily, we had our Eureka moment.  My colleague Harry Manley was showing me Google Earth’s historical Aerial imagery.  I knew one Aerial photography flight had just happened to catch some of our trenches in 2005 being excavated, perhaps it was in Google Earth’s historical Aerial Imagery? Harry moved the slider to 2005. There were the trenches.

We could then adjust our transformation so that our trench outlines fit exactly, use the same formula for other applicable data and produce similar work-flows for the rest of our material. If we were doing it now, the “on the fly” re-projection in open-source GIS programs like Qgis is actually pretty amazing, as is it’s KMl export.

Google’s  brought GI and GIS map data to everyone (in fact they’ve made it ubiquitous, recently celebrating 1 billion downloads in September). Anyone can now create, edit and share the geography that interests them, from our Stonehenge Landscape data to Chinese Military Installations.

Google Under-the-Earth: Seeing beneath Stonehenge Launched!

Google Under-the-Earth: Seeing beneath Stonehenge project has launched. You can now download a .kmz file, and then use Google Earth to explore some of the Stonehenge Riverside Project results.

As I’ve blogged before, I’ve been involved in this project from the inception, and it’s great to see it finally released to the public after all the hard work of all the contributors. This data hasn’t even been formally published yet!

We built most of this using Google’s free applications, exporting original files from Esri ArcGIS. It shows what’s achievable using the suite of Google products out there.

The project was funded by the Google Research Program.

Google Under-the-Earth: Seeing beneath Stonehenge

Here’s a video offering a glimpse of the forthcoming  Google Under-the-Earth: Seeing beneath Stonehenge project due to launch soon.

I’ve been involved in this project from the inception, and I’m really pleased how the final product is shaping up. Users will be able to download a .kmz file, and then use Google Earth to explore the Stonehenge Riverside Project results, as the video teaser above shows.

We built most of this using Google’s free applications, exporting original files from Esri ArcGIS. It shows what’s achievable using the suite of Google products out there.

It’s been a real labour of love, but I’m thrilled it’s going to be made available to everyone. Have a look at Lawrence Shaw’s blog as well, he produced the fantastic tours of the landscape and added so much to the project.

News of the launch will be placed on the web pages of Bournemouth University at Google Under-the-Earth: Seeing beneath Stonehenge. The project was funded by the Google Research Program.

Songo Mnara

I returned last week from Songo Mnara, where I was providing GNSS survey and GIS support.

View from Palace

View from Palace entrance

It was an amazing 17 days, living and working on a true desert Island. No freshwater, apart from supplies ferried from the mainland, made me appreciate the bounty a tap provides. Experience has taught me that this “first world” appreciation will fade within a few weeks, but for now it’s good to be reminded how lucky I am.

The  Zamani Project uses ground-based LiDAR scanners to record the well preserved buildings, not just here but all over Africa. They kindly passed on all of their GIS data, at no cost.

This was an incredible jumpstart to my work, and allowed on-site demonstration of why GI information feeds so successfully into everyday project management. Even now, watching peoples’ reactions as surveyed data slots into position on screen over layers of GI data, their “Wow” still brings a smile.

With proprietorial software in short supply, we made great use of Quantum GIS. Being able to distribute this freely, with few restrictions and no cost, allowed everyone who wanted copies of the GI data, to view and manipulate it. This wouldn’t have happened otherwise.

I had a great time, due mainly to the leadership from Dr Jeffrey Fleisher and Dr. Stephanie Wynne-Jones. Hopefully I can return next field season in 2013, and I’m already looking forward to it.


View Songo Mnara in a larger map

Market Research…and an old friend

I’m about to receive survey results from a selection of regional businesses, focused on their use and knowledge of GI and GIS, or lack of it.  I put it together with the Market Research Group, based at BU. Apparently we have more than 100 respondents, which makes it more ‘scientific’ than survey results in some shampoo adverts.

Focused on Consultancy, as I am, I’ll be intrigued to see the responses, I’m not aware of other recent surveys like this.

Though GI industry representatives continually mention how GIS is all important to every business,  has this news been communicated, particularly it’s use as a strategic tool?

I’ll let you know.

New Commodore 64

I’ve had this email and tweeted to me repeatedly today, and I can see why:

New Commodore 64

New Commodore 64

Takes me back to the excitement of this:

Commodore 64 Basic V2

Commodore 64 Basic V2..Ready!


Where’s that pre-order button?

All images from New Commodore 64


Setting up…

“Forget the first steps, start the journey with a leap.”

Good advice, so it’s time to jump-start this blog. It’s been sat patiently for two years, collecting lint and electrons. I’ll be changing the look and updating as I go, in the meantime, here’s a good old testament inspired “mission statement” for this blog.

“There the wicked will cease from troubling, and there the weary be at rest” Job, 3, 17