Esther Kokmeijer

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/// Contribution for the book “A summary of the world” – Esther Kokmeijer (English) ///

THE CALCULATIONS FOR THE CENTRES
Jean-Georges Affholder (1939) former land surveying engineer with the National Geographical Institute (IGN) in Paris

The dictionary defines the centre of gravity as: ‘the point within something at which gravity can be considered to act; in uniform gravity it is equal to the centre of mass. 2. fig. essence, core.’

The centre of gravity is the geographical centre of a flat surface; land masses and expanses of water and continental waters were not included in the calculations. It is the point on which the ‘flat continent’ balances. If you were to cut out the continent and balance it on a pencil, there is only one point on which the continent would be in total horizontal balance.

Curriculum Vitae
“After I graduated from the National School of Geographical Sciences (ENSG), in 1962, I went to work with the land surveying service of the National Geographical Institute (IGN) where I stayed for ten years. Initially I did field work: in 1965 I went on a five-month mission in the Algerian Sahara. On assignment for the Algerian government I mapped the areas to a scale of 1:200,000 using astrogeodesy (land surveying on the basis of astronomy). In France I worked on triangulations, on measurements of the so-called vertical deviation, and on a wide range of ‘exceptional land survey works’, in particular photographing the passage of satellites against a star-lit sky. This is known as geometric astronautic geodesy (land surveying via satellites), which was developed in the nineteen sixties i.e. long before any global positioning system (GPS).

From 1968 I was involved in the applied informatics of land surveying and in particular in astronautic geodesy. At a congress in Prague in April 1968 (in the middle of the Prague Spring, to which Russian tanks would put an end in August of that year), I explained that thanks to the emergence of informatics, matrix calculation was more suitable than spherical trigonometry for the ‘star reduction during daylight’ (deriving the exact position of the stars in respect of a given place on earth).

From 1972 I concentrated on the computerisation of documentation and I was later appointed Head of Informatics Education at the ENSG, a position I held until 1982. After that I spent just over three years writing computer programmes in the scope of the SPOT programme (Satellites pour l’Observation de la Terre)(1).

In 1986 the service appointed me to develop new activities. Among other things I was involved in the automatic reading of documents, until the first operational scan system was launched on the market as a result of which the IGN discontinued this line of research.

During that same period I was asked to calculate the centre of the European Community, then twelve member states. I was asked to do this partly because our service was often asked to do that kind of work, and also because, with my past experience as a land surveyor, I was particularly experienced in calculations on the basis of ellipsoid projection. 

In 1991 I joined the IGN research service where, until I retired in 2004, I was involved in the so-called automatic generalisation of topographical maps. In other words: developing software that would convert a map of a given scale (e.g. 1:25,000) to a map of a smaller scale (e.g. 1:100,000 or 1:250,000). A great many research centres all over the world had been working on this since the seventies, the average lay person has no idea of the problems the work entails. In the eighties it was even sometimes suggested that the problem was irresolvable.

Allow me to tell you a little of the history of determining geographical centres.
In 1984, at the request of the newspaper Le Monde, the IGN determined the centre of France. At that point in time I was involved in the SPOT programme and one of my colleagues did the work, applying the means and methods then available. His method was less precise than the method I later used, but more precise than any previously used.

In 1987 an organisation whose objective it was to promote the European Idea asked the IGN to calculate the centre of the European Community, which then consisted of twelve member states. That was the first time I determined a geographical centre (2). I used maps of the continents at a scale of 1:5,000,000; these maps had been manually digitized with a view to an intended update (but no such update ever materialised).

A little anecdote: On the basis of the work Moyenne, milieu, centre (3), a two-day symposium was held, I think it was in 1989, at the Ministry of Research. I attempted to deliver a rather humorous lecture and to amuse my audience with a number of anecdotes which I felt were quite amazing. Unfortunately, a famous historian was by no means amused and she accused me that I had failed to notice that the very issue of (geographical) centres was actually a very serious matter. While I was writing my text for the book I took her criticism into account. I hope that my historian was satisfied.

I no longer recall who or which organisation first decided to determine the centre of Europe in physical terms, from the Atlantic Ocean to the Urals, in 1989. But I do remember meeting a young journalist at the time who was on her way to Lithuania where she was to make a report at the place which, according to my calculations, was where the geographical centre of Europe was situated, in Purnuskis, about twenty kilometres from Vilnius. She returned from Lithuania with a report which Paris Match, the most famous weekly magazine in France, refused. The journalist since had a highly successful career: it was Alexandra Boulat(4).

In the nineties I was asked to calculate the centres of several French départements and regions. The Bretons were disappointed that the place I had calculated was not the same as the place the Holy Virgin was said to have indicated during an apparition in the seventeenth century! I actually felt that the two points were very close to each other and anyway, the administrative borders of the current region of Brittany are not the same as the historical province of Brittany either.”

About the geographical centres
A centre of gravity is best explained with a simple analogy. Cut out a cardboard polygon and place it on a point at which it stays in balance; that is its centre of gravity.

In reality there is much more to it than that. The Breton coastline is a problem, for example. The length of that coastline depends on the scale of the map you use. The larger the scale, the more details you will see and the longer the coastline becomes, ad infinitum. But while the length of the Breton coastline might not have any mathematical meaning, the surface area of Brittany does. And calculating the centres of gravity is done using surface areas.

The calculation is based on the surface area reduced to sea level, without the areas of water. There is a simple solution for islands: you deal with them in pairs. In other words: you determine the centre of gravity of the one island and that of the other, and draw a straight line between the two. The centre of gravity can now be situated on this line. Working in pairs in this way, you can calculate the centre of gravity the whole archipelago. For Finland I had to allow for thousands of islands. Luckily that is a fairly easy calculation for a computer program.

Calculating the centre of Europe had no practical purpose whatsoever and nothing at all to do with my job at the IGN. But it was fun to do. The institute did not profit in any way from my calculations, except in terms of name recognition(5). My first calculation, that of the physical Europe in 1987, achieved a certain amount of success in the media. There has always been a great deal of media interest in geographical centres. For me it was a hobby. Sometimes my calculations gave rise to controversy. When, in 2004, I situated the geographical centre of the twenty-five member states of Europe in Germany, a German newspaper wrote: those French can’t count. They thought that the centre could be calculated simply by taking the extreme longitudes and latitudes of Europe. That’s the kind of calculation a twelve-year old could have done. Oh, there are so many other definitions of centre. You just have to know which centre we’re talking about. I chose to determine the geometric centre.”

About the National Geographic Institute (IGN)
“Why was the institute called ‘geographic’, a name which is likely to be confused with university geographic institutes?

In fact the term ‘surveying’ or ‘geographic’ engineer goes back to the middle of the eighteenth century. There was no mention of ‘cartographer’ yet, a term which first appeared in 1820 in French. The term ‘cartography’ did not appear until 1832 and originally denoted the collective actions which led to the realisation of a map. Nowadays the term, in professional jargon, denotes the final stages only: drawing, printing, generalisation etc, and should be distinguished from the surveying, topography and photogrammetry.

In 1750 Louis XV decided to have a map of France made on one hundred and seventy pages at a scale of 1:86,400. This map was made by the Dépôt de la Guerre, a war depot set up in 1688 by Louvois, a minister under Louis XIV, for the storage of military archives and cartographic works. These were initially made by engineers from the various regiments. Around that time a corps of geographical engineers was formed.

In 1887 the Dépôt de la Guerre was replaced by the Service Géographique de l’Armée, the geographical service of the army. In 1940 this became a civil service: the IGN.”

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(1)The distance detection programme SPOT was set up by France in cooperation with Belgium and Sweden. Thanks to the constellation of the various satellites in orbit round the earth, the earth can be observed, almost in its entirety, in a single day. Above forty degrees longitude, any random point can be observed on any random day of the year; only a narrow strip of approximately 250 kilometres remains inaccessible.

(2) In 1987 Affholder situated the geographical centre of the twelve-nation Europe in Saint-André-le-Coq in the French département of Puy-de-Dôme. Three years later, following the reunification of East and West Germany, the geographical centre moved fifty kilometres eastward, to Saint-Clément in the département of Allier. In 1995, after Finland, Austria and Sweden had joined the EU, the geographical centre came to be near Viroinval in Belgium, in 2004 (twenty-five member states) it moved to Kleinmaischeid in Germany, and since 1 January it is in Gelnhausen, in the German state of Hessen. The centre of the European Union has therefore come to be situated less than fifty kilometres from the head office of the European Central Bank in Frankfurt.

(3)Moyenne, Milieu, Centre: histoires et usage, edited by Jacqueline Feldman (et al), Paris 1991. Includes a contribution by Jean-Georges Affholder.

(4)Alexandra Boulat made an international name for herself with photographic reports of armed conflicts in former Yugoslavia, Afghanistan and Iraq. She worked for such magazines as Time, Newsweek, New York Times Magazine and National Geographic, and won the World Press Photo in 2003.
She died in October 2007 at the age of 45, following a brain haemorrhage she suffered in June while reporting from Ramallah on the West Bank for Paris Match.

(5)It cannot be a coincidence that a French institute should have calculated the centre of Europe. Ever since Celtic times, people in that country have tried to determine a geographical centre that coincides with a political centre. The druids placed the centre of Gaul in Mediolanum, now Chateaumeillant in the département of Cher, inhabited by a people that laid claim to the leadership over the other Gallic peoples.