Monday, 12 October 2015

Principles of cartographic design

I was following an email discussion late last week regarding the search for some online principles of cartographic design. Many exist in various books that those with a cartographic background are aware of but, of course, people prefer to want their information for free via their glass lens on the world. Actually, there aren't many online. Ordnance Survey have some here which are certainly worth a look but it's still books that get into the detail you'll need if you're going to really learn about cartography.

Some see principles as rules but that gives them a status of authority and absoluteness that suggests they shouldn't be broken at all, at any cost. There are some rules in cartography (such as which govern effective text placement; or to process data into a rate for a choropleth map) but I see principles as guidelines that provide oversight for the map you're making. I'm happy for them to be challenged and broken and innovation often comes from that process. I'm also strong of the opinion that if you know some principles you're in a good position to also know when and how to challenge them in your design. You'll also be able to easily recognize when a map eschews principles and simply fails.

One of my friends from the UK, Alan Collinson (of Geo-Innovations) reminded everyone in the discussion of the principles that the British Cartographic Society Design Group drew up some time ago. I'm guessing this would be the late nineties or thereabouts. I have a vague memory of them at the time but the internet wasn't then what it is now and these ideas tend to get lost. Many good cartographic minds and practitioners conceived of them so I thought it worth posting them here, as is. Some may find them helpful. Interestingly, the principles are prefaced with three statements and as you read through you can see the underlying current of fear about the spectre of GIS as a threat to cartographic design. Perhaps the parallel now is the threat to quality by ubiquitous citizen mapping?


The purpose of cartographic design is to focus the attention of the user.
The Principles of cartographic design are timeless, the results are not.
The rules of cartographic design can be taught and can be learnt, principles and concepts have to be acquired and practiced.


Without a grasp of concept the whole of the design process is negated.  The parts embarrass the whole. Once concept is understood, no design or content feature will be included which does not fit it. Design the whole before the part. Design comes in two stages, concept and parameters, and detail in execution. Design once, devise, design again User first, user last.  What does the user want from this map? What can the user get from this map? Is that what they want? If a map were a building it shouldn’t fall over.

Important things must look important, and the most important thing should look the most important."They also serve who only stand and wait". Lesser things have their place and should serve to complement the important. From the whole to the part, and all the parts, contributing to the whole. Associated items must have associated treatment. Harmony is to do with the whole map being happy with itself. Successful harmony leads to repose. Perfect harmony of elements leads to a neutral bloom. Harmony is subliminal.

Great design tends towards simplicity (Bertin). Its not what you put in that makes a great map but what you take out. The map design stage is complete when you can take nothing else out. Running the film of an explosion backwards, all possibilities rush to one point. They become the right point.  This is the map designer's skill. Content may determine scale or scale may determine content, and each determines the level of generalisation (sacrifice).

Maximum information at minimum cost (after Ziff). How much information can be gained from the map, at a glance? GIS has forced cartography into one of its utility phases, the necessary information but without visual interpretation. What we need is functionality, not utility.  Design makes utility functional.  Design increases the information transfer process because a
well designed map has clarity.  Clarity is achieved by compromise. All designs are a compromise.  A compromise between what could be shown and what can be read and understood.

Engage the emotion to engage the understanding. Here is the crux for all GIS Systems.  The one thing that cartographers acknowledge when creating maps is that it takes something out of them. They have expended some invisible emotional energy in the act of creation. When a GIS system cries over its map then I believe we cartographers will be defunct. Design with emotion to engage the emotion.  Only by feeling what the user feels can we see what the user sees. Good designers use Cartographic fictions, Cartographic impressions, cartographic illusions to make a map.  All of these have emotive contents. The image is the message. Good design is a result of the tension between the environment (the facts) and the designer. Only when the reader engages the emotion, the desire, will they be receptive to the maps message. Design uses aesthetics but the principles of aesthetics are not those of design.  We are not just prettying maps up.

There you go...maybe we should think of updating them? Actually, I a book I'm currently writing with Damien Saunder called 'Cartography.' A book. Not a web site. We're excited by it...a modern book on cartographic design that delivers principles and practical advice. As of today we're about half way through writing it and hoping it'll be published by the middle of next year.

Tuesday, 6 October 2015

Voronoi footballs

Via Keir Clarke's Maps Mania I saw the latest voronoi designed map this morning. Made by Guus Hoekman, the map uses voronoi polygons to subdivide the world such that each polygon represents a spatial partition that contains one football club.

It's a neat coded solution for the novice football supporter to simply locate themselves and then determine which is their closest team. 

Why get all cartonerdy about it then? Well, partly because I've not had a good cartonerd rant for a few months (despite several maps causing much ire) but moreso, because maps like these never seem to go beyond providing a small technical solution to an overly simplistic question. The real world is far more complex than maps like this ever try to take on. Closest is not necessarily the way you choose your team.

Football (probably most sport fandom) is a hugely complex soup. There are three rules for supporting an English football team. First, you support the team you were born and raised closest to so in that respect the map could be deemed a reasonable effort. Proximity gives ample opportunity for the young supporter to shift allegiance if parents move around a bit as well, before your fandom settles. The point here is that you don't need a map to tell you you're local birth-right football team but being close doesn't always stack up either. County or city boundaries, rivers and other features can all modify proximity.

Second, you support the team your father supported. Before someone screams 'what about your mother's team? Well, to be honest your father should have already got that covered if he chose his partner wisely. This is always a good option if your parents moved to somewhere bereft of a decent team yet hailed from a footballing mecca. If neither of these solutions appeal, you simply support Manchester United because that's what you do if you've never been anywhere near Manchester.

Regardless of these basic rules, supporting a team is so much more than a geometric solution that a map can provide. It's about territory, local rivalry, physical and social geographies and all sorts of other real world dimensions that cannot be adequately represented by voronoi polygons.

The map has omissions. It fails to show the lower leagues of most countries. It only considers the men's game and for some countries, such as the U.S. the women's game is arguably more popular anyway.

The map allows the classic 'neutral' fan to select a team based on tier. Why would anyone bother with lower leagues? Let's take a look at how this plays out by selecting just the first tier teams in an area I am familiar with.

So in England, being from Nottingham, the map would encourage me to support Leicester City. An odd choice since local rivalry dictates this is impossible. Worse, the map suggests that I would likely be sat alongside someone from Derby. This is utterly absurd. And look more closely...the English Premier League teams are on the same map as the Welsh Football League. They just don't compare.

My team is Nottingham Forest. I was born in Nottingham and raised 2 miles from the ground, on the right side of the River Trent to be a Forest fan. If my parents had decided to live on the other side of the river I'd have been a Notts County fan (shudder!)...or else I might have invoked the second principal and supported Chelsea since my father's lineage gave me that option. My mother's background was irrelevant...Rotherham United - footballing wilderness. I was fortunate when growing up that Forest happened to be one of THE most successful teams of the era (late 70s and early 80s in particular). What a fantastic quirk of location...I'd nailed it by luck alone.

Tragically, they've not been so good recently (by recent, I mean 20+ years and at least once I vaguely considered invoking the Chelsea lineage) and are now in tier two. According to the map below I am at least I'm properly deliniated from that lot from Derby and Leicester with perfect walls erected...though not quite in the right spot based on the geography of the places themselves.


Furthermore, most of Lincolnshire remains in Forest territory and this is wrong (unless you're my brother who sadly moved in this direction but at least maintains his footballing heritage). Adding tier 3 attributes the vast expanse of flat nothingness that is Lincolnshire to Peterborough United while Forest's polygon shrinks to make way.

But that doesn't stack up either. Peterborough's average attendance is 5,600 whereas Forest's is about 20,000 so the polygon doesn't really relate to the potential pool of support. Or does it...Nottingham is a much larger city in terms of population size (310,000) that Peterborough (116,000) though much of that expanse around the town is rural and sparsely populated. So, again, voronoi representations really don't adequately represent population distribution, structure or density of the real places from which support for a team is formed.

Finally when we add all teams into the mix and look at England's best supported team again...they are represented by one of the tiniest polygons. Most of Manchester United's fans live outside of this polygon and it's likely many of Manchester City's fans live inside it.

So voronoi's look nice, they are easy to make and when you have a point-based dataset you can compute them to demarcate space. Whether they make any sense whatsoever is down to understanding the input data and the questions you want the resulting map to support. In this case, the geography of football fandom is so much more complex than a voronoi can ever hope to show.

Want a more considered view of football fandom and how it is spatially formed? Check out James Cheshire and Oliver Uberti's Football Tribes map in their superb book The Information Capital. Football Tribes:

It's based on tweets (a dataset I've often been critical of) but least it demonstrates the complex structure of football fandom and how it is in no way possible to use a voronoi polygon as a way of reflecting on that geography.

Ultimately, data isn't just data. It has context. It often requires a deeper understanding and domain knowledge before you begin to represent or map it. Often, it's incapable of being used on its own to support meaning.

Wednesday, 17 June 2015

True Size of Africa - now in three dee!

A few years back, designer Kai Krause made his multi-viral 'True Size of Africa' graphic. It's what got me riled enough to start this blog and it was the focus of my first post as I re-drew the map using shapes from an appropriate equal area projection. I got called a 'marauding cartonerd' for making some salient observations and making the corrections.

He got a bit miffed that people were pointing out errors in his work but he remained committed to the cause of simply trying to show that Africa is a big place. His wholly misleading map constantly bubbles up on the internet. The critiques get largely ignored because few care about accuracy and the world keeps turning. Except he's only gone and updated the graphic.

Scientific American published his new graphic in a blog entitled Africa Dwarfs China, Europe and the U.S. in a section called Graphic Science.

Nervously, I went over and took a look...and this is what I saw:

Now let's be clear, the aim of educating people that the Mercator projection distorts our perception of reality and that Africa as a continent has suffered more than most is commendable. Fighting immappancy (as Krause described this lack of understanding of geography) is also close to my heart. But using maps incorrectly is where I get all cartonerdy.

You'd think, perhaps, that Krause might have taken some of the criticism on the chin and used this update as a way to correct his own immappancy. You'd also think that in a publication that profers the importance of 'science' that accuracy might be important. You also may presume that anything in the 'Graphic Science' section would be scientifically accurate in its visual display. Let's see eh?

Like many, Krause has embraced 3D. People love 3D. It looks cool and literally gives maps depth. So this new graphic is attention grabbing because of it's three dee-iness alone.

However - 3D blocks in perspective wrapped round a globe creates visual distortions. In just the same way that on a flat map that uses Mercator the north and south are distorted relative to the equator, on a virtual globe we see distortions in the relative size and shape of features as they move away from the viewing point - the point closest to us as map readers. China therefore appears predominant and his rendering of Western Europe starts to diminish as it begins to wrap around the curve of the globe. So, visually, comparing like for like from a single point of view on a 3D perspective drawing (or globe) isn't a good way of showing comparisons...particularly when it's based on the relative size of areas (I wrote of these issues in a separate blog).

Notwithstanding the visual problems with interpreting the relative size of shapes across a curved surface, if Krause has at least got all his shapes in proportion during the construction of the graphic then we might at least be able to assume some semblance of relative size. BUT...the sizes and shapes didn't quite look right to me so I popped open my GIS package of choice and played with some shapes.

Given I re-drew the original 2D version I thought it only natural to re-draw the 3D version so here's my attempt at re-making his map with the same countries on a virtual globe:

I had difficulties re-making his map like-for-like for the simple reason that the real world shapes are not the same as he presents. Here's where Krause's map seems to fail:

  • China is not the same shape and has been warped to fit neatly over Madagascar.
  • The contiguous United States is much larger than he presents.
  • Krause included Germany and a partial set of Eastern European countries. There simply isn't room.
  • The real India is larger than Krause represents.

Of course I'm being cartographically pedantic again but if the very thing you purport to show is misrepresenting reality I don't think artistic license is a sufficiently good excuse. Yes, you could argue it's only a little bit wrong but if you're going to do something, why not do it right? Few who look at the new graphic will even think to question its authority and they will glean a distorted picture. That's the real issue.

The world will likely jump on his graphic and proclaim it as a great way to visualize differences in the size of areas. Like his 2D attempt, it's inaccurate. Will anyone care? I do. Should I have made a 3D version? Probably not. The 2D version is far more useful at supporting visual comparison of areas. Adding perspective and extruding the shapes to volumetric blocks just adds unnecessary visual noise that creates problems for our human processing of the map's message.

ht to @cartocalypse for the link

Sunday, 7 June 2015

Bend it like Mercator

After their win in the Champions League final yesterday, the 101 Great Goals blog published a piece on the relative location of FC Barcelona's triumvirate of South American strikers. They picked up a map from Reddit that showed their birthplaces as being positioned in such a way that you can draw a perfectly straight line between them on Google Maps.

Here's the map:

A headline writer's dream...arguably the three best strikers in the world all born in formation as well as playing in formation for the world's best team. An easy map to make...take a pen and draw a line across the map to link three red symbols, each of which is about 50 miles in diameter in real world units. Job done.

Except the map is incorrect...which makes the headline potentially incorrect too. A straight line between two places on the globe becomes a curved line when projected using Web Mercator (which the Google Map used by the author is in this case). You cannot simply draw a straight line on the map and infer that it represents a straight line on the curved surface of the globe - because it doesn't.

Here's what the line looks like on a virtual globe as if looking from Messi's birthplace to Neymar's birthplace:

And when we place that line back onto a projected flat map, here's the outcome:

The line now has a slight curve to it but with symbols about 10 miles in diameter it still just nicks the edge of the town where Suarez was born. If I'd used smaller symbols I could have shown the line doesn't pass through Salto, Uruguay. If I'd used big red blobs like the original then of course the line would pass through Salto. Built correctly, we not only get an accurate map...but one that supports the story even better!

OK, we're talking small margins here but the author of the original map got very lucky simply because of the quirk of geography relating to the three players he chose to link on the map. Because the three locations are relatively close to one another (in global terms) and they are also only 30 degrees or so south of the equator we don't see a massive distortion in the line. It has a curve, yes...but only a slight one.

But what if we look at three other footballers? Wayne Rooney was born in Croxteth, Liverpool. Harry Kewell in a Sydney suburb in Australia; and C. V. Pappachan, the famous (?) former Indian footballer born in Thrissur. Here's their map:

As far as I know there is nothing at all to link these three footballers but if we'd taken the mapping approach used to link Barcelona's strikers we'd also get a perfect straight line passing from Liverpool in the UK, all the way to Sydney, Australia via Thrissur on the southern tip of India.

If you got in a plane and flew the straight line route between the UK and Sydney the closest you get to Thrissur is about 2,500 miles. The red line shows the planar version of a straight line projected on Web Mercator. I included the Barcelona striker's line for scale which shows that smaller distances, particularly near the equator, 'appear' less curvier.

News aggregators, blogs and, well, pretty much anyone should question maps. They lie. They are terrible at telling porkies. Worse. Most map readers don't know they're being fed a lie because they look authoritative; and they don't know that the maker of the map they're looking at didn't know the pitfalls of their approach either.

As it turns out, Barça's strikers do happen to have been born close enough to almost lie in a straight line on the globe and on the map. The curve on the projected map tells the accurate story. Try telling the story using three other footballers who appear to have been born along a straight line on a map and chances are, they weren't.

Hat Tip to Brian Timoney for the tweet about this map.