# Banksy and the mathematicians

Assuming you’ve heard of Banksy (if not, he’s an internationally known graffiti artist), then you understand that no one knows his real name for certain although there are strong suspicions, as of 2008, that he is Robin Gunningham. It seems the puzzle has aroused scientific curiosity according to a March 4, 2016 article by Jill Lawless on CBC (Canadian Broadcasting Corporation) News online,

Elusive street artist Banksy may have been unmasked — by mathematics.

Scientists have applied a type of modelling used to track down criminals and map disease outbreaks to identify the graffiti artist, whose real name has never been confirmed.

The technique, known as geographic profiling, is used by police forces to narrow down lists of suspects by calculating from multiple crime sites where the offender most likely lives.

The March 3, 2016 article in The Economist about the Banksy project describes the model used to derive his identity in more detail,

Their system, Dirichlet process mixture modelling, is more sophisticated than the criminal geographic targeting (CGT) currently favoured by crime-fighters. CGT is based on a simple assumption: that crimes happen near to where those responsible reside. Plot out an incident map and the points should surround the criminal like a doughnut (malefactors tend not to offend on their own doorsteps, but nor do they stray too far). The Dirichlet model allows for more than one “source”—a place relevant to a suspect such as home, work or a frequent pit stop on a commute—but makes no assumptions about their number; it automatically parses the mess of crime sites into clusters of activity.

Then, for each site, it calculates the probability that the given array of activity, and the way it is clustered, would result from any given source. Through a monumental summing of probabilities across each and every possible combination of sources, the model spits out the most likely ones, with considerable precision—down to 50 metres or so in some cases.

While this seems like harmless mathematical modeling, Banksy lawyers were sufficiently concerned over how this work would be promoted that they contacted the publisher according to Jonathan Webb’s March 3, 2016 article for BBC (British Broadcasting Corporation) News online,

A study that tests the method of geographical profiling on Banksy has appeared, after a delay caused by an intervention from the artist’s lawyers.

Scientists at Queen Mary University of London found that the distribution of Banksy’s famous graffiti supported a previously suggested real identity.

The study was due to appear in the Journal of Spatial Science a week ago.

The BBC understands that Banksy’s legal team contacted QMUL staff with concerns about how the study was to be promoted.

Those concerns apparently centred on the wording of a press release, which has now been withdrawn.

Taylor and Francis, which publishes the journal, said that the research paper itself had not been questioned. It appeared online on Thursday [March 3, 2016] unchanged, after being placed “on hold” while conversations between lawyers took place.

The scientists conducted the study to demonstrate the wide applicability of geoprofiling – but also out of interest, said biologist Steve Le Comber, “to see whether it would work”.

The criminologist and former detective who pioneered geoprofiling, Canadian Dr Kim Rossmo [emphasis mine] – now at Texas State University in the US – is a co-author on the paper.

The researchers say their findings support the use of such profiling in counter-terrorism, based on the idea that minor “terrorism-related acts” – like graffiti – could help locate bases before more serious incidents unfold.

I believe the biologist Steve Le Comber is interested in applying the technique to epidemiology (study of patterns in health and disease in various populations). As for Dr. Rossmo, he featured in one of the more bizarre incidents in Vancouver Police Department (VPD) history as described in the Kim Rossmo entry on Wikipedia (Note: Links have been removed),

D. Kim Rossmo is a Canadian criminologist specializing in geographic profiling. He joined the Vancouver Police Department as a civilian employee in 1978 and became a sworn officer in 1980. In 1987 he received a master’s degree in criminology from Simon Fraser University and in 1995 became the first police officer in Canada to obtain a doctorate in criminology.[1] His dissertation research resulted in a new criminal investigative methodology called geographic profiling, based on Rossmo’s formula. This technology was integrated into a specialized crime analysis software product called Rigel. The Rigel product is developed by the software company Environmental Criminology Research Inc. (ECRI), which Rossmo co-founded.[2]

In 1995, he was promoted to detective inspector and founded a geographic profiling section within the Vancouver Police Department. In 1998, his analysis of cases of missing sex trade workers determined that a serial killer was at work, a conclusion ultimately vindicated by the arrest and conviction of Robert Pickton in 2002. A retired Vancouver police staff sergeant has claimed that animosity toward Rossmo delayed the arrest of Pickton, leaving him free to carry out additional murders.[3] His analytic results were not accepted at the time and after a dispute with senior members of the department he left in 2001. His unsuccessful lawsuit against the Vancouver Police Board for wrongful dismissal exposed considerable apparent dysfunction within that department.[1]

It’s still boggles my mind and the reporters covering story that the VPD would dismiss someone who was being lauded internationally for his work and had helped the department solve a very nasty case. In any event, Dr. Rossmo is now at Texas State University.

Getting back to Banksy and geographic profiling, here’s a link to and a citation for the paper,

Tagging Banksy: using geographic profiling to investigate a modern art mystery by Michelle V. Hauge, Mark D. Stevenson, D. Kim Rossmo & Steven C. Le Comber. Journal of Spatial Science DOI:  10.1080/14498596.2016.1138246 Published online: 03 Mar 2016

This paper is behind a paywall.

For anyone curious about Banksy’s work, here’s an image from this Wikipedia entry,

Stencil on the waterline of The Thekla, an entertainment boat in central Bristol – (wider view). The section of the hull with this picture has now been removed and is on display at the M Shed museum. The image of Death is based on a nineteenth-century etching illustrating the pestilence of The Great Stink.[19] Artist: Banksy – Photographed by Adrian Pingstone

# The Code; a preview of the BBC documentary being released in Canada and the US

The three episodes (Numbers, Shapes, and Prediction)  of The Code, a BBC (British Broadcasting Corporation) documentary featuring Professor Marcus du Sautoy, focus on a ‘code’ that according to du Sautoy unlocks the secrets to the laws governing the universe.

During the weekend (June 16 & 17, 2012) I had the pleasure of viewing the two-disc DVD set which is to be released tomorrow, June 19, 2012, in the US and Canada.  It’s a beautiful and, in its way, exuberant exploration of patterns that recur throughout nature and throughout human endeavours. In the first episode, Numbers, du Sautoy relates the architecture of the Chartres Cathedral (France) , St. Augustine‘s (a Roman Catholic theologian born in an area we now call Algeria) sacred numbers, the life cycle of the periodic cicada in Alabama, US and more to number patterns. Here’s an excerpt of du Sautoy in Alabama with Dr. John Cooley discussing the cicadas’ qualities as pets and their remarkable 13 year life cycle,

In the second episode, Shapes,  du Sautoy covers beehive construction (engineering marvels), bird migrations and their distinct shapes (anyone who’s ever seen a big flock of birds move as one has likely marveled at the shapes the flock takes as it moves from area to another), computer animation, soap bubbles and more, explaining how these shapes can be derived from the principle of simplicity or as du Sautoy notes, ‘nature is lazy’. The question being, how do you make the most efficient structure to achieve your ends, i.e., structure a bird flock so it moves efficiently when thousands and thousands are migrating huge distances, build the best beehive while conserving your worker bees’ energies and extracting the most honey possible, create stunning animated movies with tiny algorithms, etc.?

Here’s du Sautoy with ‘soap bubbleologist’ Tom Noddy who’s demonstrating geometry in action,

For the final episode, Prediction, du Sautoy brings the numbers and geometry together demonstrating repeating patterns such as fractals which dominate our landscape, our biology, and our universe. du Sautoy visits a Rock Paper Scissors tournament in New York City trying to discern why some folks can ‘win’ while others cannot (individuals who can read other people’s patterns while breaking their own are more successful), discusses geographic profiling with criminal geographic profiler Prof. Kim Rossmo, Jackson Pollock’s paintings and his fractals, amongst other intriguing patterns.

I paid special to the Rossmo segment as he created and developed his geographic profiling techniques when he worked for the Vancouver (Canada) Police Department (VPD) and studied at a nearby university. As this groundbreaking work was done in my neck of the woods and Rossmo was treated badly by the VPD, I felt a special interest. There’s more about Rossmo’s work and the VPD issues in the Wikipedia essay (Note: I have removed links from the excerpt.),

D. Kim Rossmo is a Canadian criminologist specializing in geographic profiling. He joined the Vancouver Police Department as a civilian employee in 1978 and became a sworn officer in 1980. In 1987 he received a Master’s degree in criminology from Simon Fraser University and in 1995 became the first police officer in Canada to obtain a doctorate in criminology. His dissertation research resulted in a new criminal investigative methodology called geographic profiling, based on Rossmo’s formula.

In 1995, he was promoted to detective inspector and founded a geographic profiling section within the Vancouver Police Department. In 1998, his analysis of cases of missing sex trade workers determined that a serial killer was at work, a conclusion ultimately vindicated by the arrest and conviction of Robert Pickton in 2002. A retired Vancouver police staff sergeant has claimed that animosity toward Rossmo delayed the arrest of Pickton, leaving him free to carry out additional murders. His analytic results were not accepted at the time and after a falling out with senior members of the department he left in 2001. His unsuccessful lawsuit against the Vancouver Police Board for wrongful dismissal exposed considerable apparent dysfunction within that department.

… he moved to Texas State University where he currently holds the Endowed Chair in Criminology and is director of the Center for Geospatial Intelligence and Investigation. …

Within what appeared to be chaos, Rossmo found order. Somehow Jackson Pollock did the same thing to achieve entirely different ends, a new form of art. Here’s a video clip of du Sautoy with artist and physicist, Richard Taylor,

Intuitively, Pollock dripped paint onto his canvases creating fractals decades before mathematician, Benoit Mandelbrot, coined the phrase and established the theory.  (I wrote previously about Jackson Pollock [and fluid dynamics] in my June 30, 2011 posting.)

I gather that du Sautoy’s ‘code’ will offer a unified theory drawing together numbers, patterns, and shapes as they are found throughout the universe in nature  and in our technologies and sciences.

The DVDs offer three extras (4 mins. each): Phi’s the Limit (beauty and the golden ratio or Phi), Go Forth and Multiply (a base 2 system developed by Ethiopian traders predating binary computer codes by millenia) and Imagining the Impossible: The Mathematical Art of M. C. Escher  (Dutch artist’s [Escher] experiments with tessellation/tiling).

I quite enjoyed the episodes although I was glad to have read James Gleick‘s book, Chaos (years ago) before viewing the third episode, Prediction and I was a little puzzled by du Sautoy’s comment in the first episode, Numbers, that atoms are not divisible. As I recall, you create an atomic bomb when you split an atom but it may have been one of those comments that didn’t come out as intended or I misunderstood.

You can find out more about The Code DVDs at Athena Learning. The suggested retail cost is \$39.99 US or \$52.99 CAD (which seems a little steep for Canadian purchasers since the Canadian dollar is close to par these days and, I believe, has been for some time).

In sum, this is a very engaging look at numbers and mathematics.