Tag: maps

May 02 2015

Book review: The Information Capital by James Cheshire and Oliver Uberti

Today I review TheInformationCapitalThe Information Capital by James Cheshire and Oliver Uberti – a birthday present. This is something of a coffee table book containing a range of visualisations pertaining to data about London. The book has a website where you can see what I’m talking about (here) and many of the visualisations can be found on James Cheshire’s mappinglondon.co.uk website.

This type of book is very much after my own heart, see for example my visualisation of the London Underground. The Information Capital isn’t just pretty, the text is sufficient to tell you what’s going on and find out more.

The book is divided into five broad themes “Where We Are”, “Who We Are”, “Where We Go”, “How We’re Doing” and “What We Like”. Inevitably the majority of the visualisations are variants on a coloured map but that’s no issue to my mind (I like maps!).

Aesthetically I liked the pointillist plots of the trees in Southwark, each tree gets a dot, coloured by species and the collection of points marks out the roads and green spaces of the borough. The twitter map of the city with the dots coloured by the country of origin of the tweeter is in similar style with a great horde evident around the heart of London in Soho.

The visualisations of commuting look like thistledown, white on a dark blue background, and as a bonus you can see all of southern England, not just London. You can see it on the website (here). A Voroni tessellation showing the capital divided up by the area of influence (or at least the distance to) different brands of supermarket is very striking. To the non-scientist this visualisation probably has a Cubist feel to it.

Some of the charts are a bit bewildering, for instance a tree diagram linking wards by the prevalent profession is confusing and the colouring doesn’t help. The mood of Londoners is shown using Chernoff faces, this is based on data from the ONS who have been asking questions on life satisfaction, purpose, happiness and anxiety since 2011. On first glance this chart is difficult to read but the legend clarifies for us to discover that people are stressed, anxious and unhappy in Islington but perky in Bromley. You can see this visualisation on the web site of the book (here).

The London Guilds as app icons is rather nice, there’s not a huge amount of data in the chart but I was intrigued to learn that guilds are still being created, the most recent being the Art Scholars created in February 2014. Similarly the protected views of London chart is simply a collection of water-colour vistas.

I have mixed feelings about London, it is packed with interesting things and has a long and rich history. There are even islands of tranquillity, I enjoyed glorious breakfasts on the terrace of Somerset House last summer and lunches in Lincoln’s Inn Fields.  But I’ve no desire to live there. London sucks everything in from the rest of the country, government sits there and siting civic projects outside London seems a great and special effort for them. There is an assumption that you will come to London to serve. The inhabitants seem to live miserable lives with overpriced property and hideous commutes, these things are reflected in some of the visualisations in this book. My second London Underground visualisation measured the walking time between Tube station stops, mainly to help me avoid that hellish place at rush hour. There is a version of such a map in The Information Capital.

For those living outside London, The Information Capital is something we can think about implementing in our own area. For some charts this is quite feasible based, as they are, on government data which covers the nation such as the census or GP prescribing data. Visualisations based on social media are likely also doable although will lack weight of numbers. The visualisations harking back to classics such as John Snow’s cholera map or Charles Booth’s poverty maps of are more difficult since there is no comparison to be made in other parts of the country. And other regions of the UK don’t have Boris Bikes (or Boris, for that matter) or the Millennium Wheel.

It’s completely unsurprising to see Tufte credited in the end papers of The Information Capital. There are also some good references there for the history of London, places to get data and data visualisation.

I loved this book, its full of interesting and creative visualisations, an inspiration!

Aug 23 2014

Book review: Greenwich Time and the Longitude by Derek Howse

greenwich_timeI am being used as a proxy reader! My colleague drj, impressed by my reviewing activities, asked me to read Greenwich Time and the Longitude by Derek Howse, so that he wouldn’t have to.

There was some risk here that Greenwich Time and the Longitude would overlap heavily with Finding Longitude which I have recently read. They clearly revolve around the same subjects and come from the same place: the National Maritime Museum at Greenwich. Happily the overlap is relatively minor. Following some brief preamble regarding the origins of latitude and longitude for specifying locations, Greenwich Time starts with the founding of the Royal Observatory at Greenwich.

The Observatory was set up under Charles II who personally ordered it’s creation in 1675, mindful of the importance of astronomy to navigation. The first Royal Astronomer was John Flamsteed. Accurate measurement of the locations of the moon and stars was a prerequisite for determining the longitude at sea both by lunar-distance and clock based means. Flamsteed’s first series of measurements was aimed at determining whether the earth rotated at a constant rate, something we take for granted but wasn’t necessarily the case.

Flamsteed is notorious for jealously guarding the measurements he made, and fell out with Isaac Newton over their early, unauthorised publication which Newton arranged. A detail I’d previously missed in this episode is that Flamsteed was not very well remunerated for his work, his £100 per annum salary had to cover the purchase of instruments as well as any skilled assistance he required which goes some way to explaining his possessiveness over the measurements he made. 

Greenwich Time covers the development of marine chronometers in the 18th century and the period of the Board of Longitude relatively quickly.

The next step is the distribution of time. Towards the middle of the 19th century three industries were feeling the need for precise timekeeping: telegraphy, the railways and the postal service. This is in addition to the requirements of marine navigators. The first time signal, in 1833, was distributed by the fall of a large painted zinc ball on the top of the Greenwich observatory. Thereafter, strikingly similar balls appeared on observatories around the world.

From 1852 the time signal was distributed by telegraphic means, and ultimately by radio. It was the radio time signal that ultimately brought an end to the publication of astronomical tables for navigation. Britain’s Nautical Almanac, started in 1767, stopped publishing them in 1907 – less than 10 years after the invention of radio.

With the fast distribution of time signals over large distances came the issue of the variation between local time (as defined by the sun and stars) and the standard time. The problem was particularly pressing in the United States which spanned multiple time zones. The culmination of this problem is the International Date Line, which passes through the Pacific. Here the day of the week changes on crossing the line, a problem discovered by the very first circumnavigators (Magellan’s expedition in 1522), identified when they reached travellers who had arrived from the opposite direction and disagreed on the day of the week. I must admit to being a bit impressed by this, I can imagine it’s easy to lose track of the days on such an expedition.

I found the descriptions of congresses to standardise the meridian and time systems across multiple nations in the 1880s rather dull.

One small thing of interest in these discussions: mariners used to measure the end of the day at noon, hence what we would call “Monday morning” a mariner would call “the end of Sunday”, unless he was at harbour – in which case he would use local time! It is from 18th century mariners that Jean Luc Picard appears to get his catchphrase “Make it so!”, this was the traditional response of a captain to the officer making the noon latitude measurement. The meridian congresses started the process of standardising the treatment of the day by “civilians”, mariners and astronomers.

The book finishes with a discussion of high precision timekeeping. This is where we discover that Flamsteed wasn’t entirely right when he measured the earth to rotate at a constant rate. The earth’s rotation is showing a long term decrease upon which are superimposed irregular variations and seasonal variations. And the length of the year is slowly changing too. Added to that, the poles drift by about 8 metres or so over time. It’s testament to our abilities that we can measure these imperfections but somehow sad that they exist.

The book has an appendix with some detail on various measurements.

Not as sumptuous a book as Finding Longitude it is an interesting read with a different focus. It has some overlap too with The History of Clocks and Watches by Eric Bruton.

Aug 03 2014

Book review: Finding Longitude by Richard Dunn, Rebekah Higgitt

finding-longitudeMuch of my reading comes via twitter in the form of recommendations from historians of science, in this case I am reading a book co-authored by one of those historians: Finding Longitude by Richard Dunn (@lordoflongitude) and Rebekah Higgitt (@beckyfh).

I must admit I held off buying Finding Longitude for a while since it appeared to be an exhibition brochure, maybe not so good if you haven’t attended the exhibition. It turns out to be freestanding and perfectly formed.This is definitely the most sumptuous book I’ve bought in quite some time, I’m glad I got the hardcover version rather than the Kindle edition.

The many photographs throughout the book are absolutely gorgeous, they are of the instruments and clocks, the log books, artwork from the time. You can get a flavour from the images online here.

To give some context to the book, knowing your location on earth is a matter of determining two parameters: latitude and longitude:

  • latitude is your location in the North-South direction between the equator and either of the earth’s poles, it is easily determined by the height of the sun or stars above the horizon, and we shall speak no more of it here.
  • longitude is the second piece of information required to specify ones position on the surface of the earth and is a measure your location East-West relative to the Greenwich meridian. The earth turns at a fixed rate and as it does the sun appears to move through the sky. You can use this behaviour to fix a local noon time: the time at which the sun reaches the highest point in the sky. If, when you measure your local noon, you can also determine what time it is at some reference point Greenwich, for example, then you can find your longitude from the difference between the two times.

Knowing where you are on earth by measurement of these parameters is particularly important for sailors engaged in long distance trade or fighting. It has therefore long been an interest of governments.

The British were a bit late to the party in prizes for determining the longitude, the first of them had been offered by Phillip II of Spain in 1567 and there had been activity in the area since then, primarily amongst the Spanish and Dutch. Towards the end of the 17th century the British and French get in on the act, starting with the formation of the Royal Society and Académie des sciences respectively.

One stimulus for the creation of a British prize for determining the longitude was the deaths of 1600 British sailors from Admiral Sir Cloudsley Shovell’s fleet off the Isles of Scilly in 1707. They died on the rocks off the Isles of Scilly in a storm, as a result of not knowing where they were until it was too late. As an aside, the surviving log books from Shovell’s fleet showed that for the latitude (i.e. the easier thing to measure), measurements of the sun gave a 25 mile spread, and those from dead reckoning a 75 mile spread in location.

The Longitude Act was signed into law in 1714, it offered a prize of £20,000 to whoever produced a practicable method for determining the longitude at sea. There was something of the air that it was a problem about to be solved. The Board of Longitude was to judge the prize. The known competitor techniques at the time were timekeeping by mechanical means, two astronomical methods (the lunar distance method, and the satellites of Jupiter) and dead-reckoning. In fact these techniques are used in combination, mechanical timekeepers are simpler to use than the astronomical methods but mechanical timekeepers needed checking against the astronomical gold standard which was the only way to reset a stopped clock. Dead-reckoning (finding your location by knowing how fast you’d gone in what direction) was quick and simple, and worked in all weathers. Even with a mechanical timekeeper astronomical observations were required to measure the “local” time, and that didn’t work in thick cloud.

There’s no point in sailors knowing exactly where they were if maps did not describe exactly where the places where they were going, or trying to avoid. Furthermore, the lunar distance method of finding longitude required detailed tables of astronomical data which needed updating regularly. So alongside the activities of the longitude projectors, the state mechanisms for compiling charts and making astronomical tables were built up.

John Harrison and his timepieces are the most famous part of the longitude story. Harrison produced a series of clocks and watches from 1730 and 1760, in return he received moderate funding over the period from the Board of Longitude, you can see the payment record in this blog post here. Harrison felt hard done by since his final watches met the required precision but the Board of Longitude were reluctant to pay the full prize. Although meeting the technical specification in terms of their precision were far from a solution. Despite his (begrudging) efforts, they could not be reliably reproduced even by the most talented clock makers.

After Harrison’s final award several others made clocks based on his designs, these were tested in a variety of expeditions in the latter half of the 18th century (such as Cook’s to Tahiti in 1769). The naval expedition including hydrographers, astronomers, naturalists and artists became something of a craze (see also Darwin’s trip on the Beagle). As well as clocks, men such as Jesse Ramsden were mass producing improved instruments for navigational measurements, such as octants and sextants.

The use of chronometers to determine the longitude was not fully embedded into the Royal Navy until into the 19th century with the East Indian Company running a little ahead of them by having chronometers throughout their fleet by 1810.

Finding Longitude is a a good illustration of providing the full context for the adoption of a technology. It’s the most beautiful book I’ve read in while, and it doesn’t stint on detail.

Aug 25 2013

Book review: A history of the world in twelve maps by Jerry Brotton

HistoryOfTheWorldInTwelveMapsAs a fan of maps, I was happy to add A History of the World in Twelve Maps by Jerry Brotton to my shopping basket (I bought it as part of a reduced price multi-buy deal in an actual physical book shop).

A History traces history through the medium maps, various threads are developed through the book: what did people call the things we now call maps? what were they trying to achieve with their maps? what geography was contained in the maps? what technology was used to make the maps?

I feel the need to explicitly list, and comment on, the twelve maps of the title:

1. Ptolemy’s Geography 150 AD, distinguished by the fact that it probably contained no maps. Ptolemy wrote about the geography of the known world in his time, and amongst this he collated a list of locations which could be plotted on a flat map using one of two projection algorithms. A projection method converts (or projects) the real life geography of the spherical earth onto the 2D plane of a flat map. Project methods are all compromises, it is impossible to simultaneously preserve relative directions, areas and lengths when making the 3D to 2D transformation. The limitation of the paper and printing technology to hand meant that Ptolemy was not able to realise his map. Also the relatively small size of the known world meant that projection was not a pressing problem. The Geography exists through copies created long after the original was written.

2. Al-idrisi’s Entertainment, 1154AD. The Entertainment is not just a map, it is a description of the world as it was known at the time. This was the early pinnacle in terms of the realisation of the roadmap laid out by Ptolemy. Al-Idrisi, a Muslim nobelman, made the Entertainment for a Christian Sicilian king. It draws on both Christian and Muslim sources to produce a map which will look familiar to modern eyes (except for being upside down). There is some doubt as to exactly which map was included in the Entertainment since no original intact copies exist.

3. Hereford Mappamundi, 1300AD this is the earliest original map in the book but in many ways it is a step backward in terms of the accuracy of its representation of the world. Rather than being a geography for finding places it is a religious object placing Jerusalem at the top and showing viewers scenes of pilgrimage and increasing depravity as one moves away from salvation. It follows the T-O format which was common among such mappmundi.

4. Kangnido world map, 1402AD. To Western eyes this is a map from another world: Korea, again it only exists in copies but not that distant from the original. Here we see strongly the influence of the neighbouring China. The map is about administration and bureaucracy (and contains errors thought to have been added to put potential invaders off the scent). An interesting snippet is that the Chinese saw the nonogram (a square made of 9 squares) as the perfect form – in a parallel with the Greek admiration for the circle. The map also contains elements of geomancy, which was important to the Koreans.

5. Waldseemuller world map, 1507AD. This is the first printed map, it hadn’t really struck me before but printing has a bigger impact than simply price and availability when compared to manuscripts. Printed books allow for all sorts of useful innovations such as pagination, indexes, editions and so forth which greatly facilitate scholarly learning. With manuscripts stating that something is on page 101 of you handwritten manuscript is of little use to someone else with his handwritten copy of the same original manuscript. The significance of the Waldseemuller map is that it is the first European map to name America, it applies the label to the south but it is sometimes seen as the “birth certificate” of the USA. Hence the US Library of Congress recently bought it for $10 million.

6. Diogo Ribeiro, world map, 1529AD. A map to divide the world between the Spanish and Portuguese, who had boldly signed a treaty dividing the world into two hemispheres with them to own one each. The problem arose on the far side of the world, where it wasn’t quite clear where the lucrative spice island of Moluccas lay.

7. Gerard Mercator world map, 1569AD. I wrote about Mercator a while back, in reviewing The World of Gerard Mercator by Andrew Taylor. The Mercator maps are important for several reasons, they introduce new technology in the form of copperplate rather than woodcut printing, copperplate printing enables italic script, rather than the Gothic script that is used in woodcut printing; they make use of the newly developed triangulation method of surveying (in places); the Mercator projection is one of several methods developed at the time for placing a spherical world onto a flat map – it is the one that maintained – despite limitations.And finally he brought the Atlas to the world – a book of maps.

8. Joan Blaeu Atlas maier, 1662. Blaeu was chief cartography for the Dutch East India Company (VOC), and used the mapping data his position provided to produce the most extravagant atlases imaginable. They combined a wide variety of previously published maps with some new maps and extensive text. These were prestige objects purchased by wealthy merchants and politicians.

9. Cassini Family, map of France, 1793. The Cassini family held positions in the Paris Observatory for four generations, starting in the late 17th Century when the first geodesic studies were conducted, these were made to establish the shape of the earth, rather than map it’s features. I reviewed The Measure of the Earth  by Larry D. Ferriero which related some of this story. Following on from this the French started to carry systematic triangulation surveys of all of France. This was the first time the technique had been applied at such scale, and was the forbearer to the British Ordnance Survey, the origins of which are described in Map of a Nation by Rachel Hewitt. The map had the secondary effect of bringing together France as a nation, originally seen by the king as a route to describing his nation (and possibly taxing it), for the first time Parisian French was used to describe all of the country and each part was mapped in an identical manner.

10. The Geographical Pivot of History, Halford Mackinder, 1904. In a way the Cassini map represents the pinnacle of the technical craft of surveying. Mackinder’s intention was different, he used his map to persuade. He had long promoted the idea of geography as a topic for serious academic study and in 1904 he used his map to press his idea of central Asia as being central to the politics and battle for resources in the world. He used a map to present this idea, its aspect and details crafted to reinforce his argument.

11. The Peters Projection, 1973. Following the theme of map as almost-propaganda the Peters projection – an attempted equal-area projection – shows a developing world much larger than we are used to in the Mercator projection. Peters attracted the ire of much of the academic cartographic communities, partly because his projection is nothing new but also because he promoted it as being the perfect, objective map when, in truth it was nothing of the kind. This is sort of the point of the Peters projection, it is open to criticism but highlights that the decisions made about the technical aspects of a map have a subjective weight. Interestingly, many non-governmental organisations took to using the Peters projection because it served their purpose of emphasising the developing world.

12. Google Earth, 2012. The book finishes with a chapter on Google Earth, initially on the technical innovations required to make such a map but then moving on to the wider commercial implications. Brotton toys with the idea that Google Earth is somehow “other“ from previous maps in its commercial intent and the mystery of its methods, this seems wrong to me. A number of the earlier maps he discusses were of limited circulation and one does not get the impression that methods were shared generously. Brotton makes no mention of the Openstreetmap initiative that seems to address these concerns.

In the beginning I found the style of A History a little dry and academic but once I’d got my eye in it was relatively straightforward reading. I liked the broader subject matter, and greater depth than some of my other history of maps reading.

Jun 29 2013

Book review: Chasing Venus by Andrea Wulf

ChasingVenusI’ve been reading more of adventurous science of the Age of Enlightenment, more specifically Andrea Wulf’s book Chasing Venus: The Race to Measure the Heavens the scientific missions to measure the transit of Venus in 1761 and 1769.

Transits occur when a planet, typically Venus, lies directly between the earth and the Sun. During a transit Venus appears as a small black disc on the face of the sun. Since it’s orbit is also inside that of earth Mercury also transits the sun. Solar eclipses are similar but in this case the obscuring body is the moon, and since it is much closer to earth it completely covers the face of the sun.

Transits of Venus occur in pairs, 8 years apart separated by 100 or so years, they are predictable astronomical events. Edmund Halley predicted the 1761/1769 pair in 1716 and in addition proposed that the right type of observation would give a measure of the distance from the earth to the Sun. Once this distance is known distances of all the other planets from the sun can be calculated. In the same way as a solar eclipse can only be observed from a limited number of places on earth, the transit of Venus can only be observed from a limited number of places on earth. The observations required are the time at which Venus starts to cross the face of the sun, ingress, and the time at which it leaves, egress. These events are separated by several hours. In order to calculate the distance to the sun observations must be made at widely separate locations.

These timings had to be globally calibrated: some one in, say, London, had to be able to convert the times measured in Tahiti to the time London. This amounts to knowing precisely where the measurement was made – it is the problem of the longitude. At this time the problem of the longitude was solved given sufficient time, for land-based locations. It was still a challenge at sea.

At the time of the 1761/69 transits globe spanning travel was no easy matter, when Captain Cook landed on Tahiti in 1769 his was only the third European vessel to have done so, other ships had arrived in the two previous years; travel to the East Indies although regular was still hazardous. Even travel to the far North of Europe was a challenge, similarly across Russia to the extremes of Siberia. Therefore much of the book is given over to stories of long, arduous travel not infrequently ending in death.

Most poignant for me was the story of Jean-Baptiste Chappe d’Auteroche who managed to observe the entirety of both transits in Siberia and California but died of typhus shortly after observing the lunar eclipse critical to completing the observations he had made of Venus. His fellow Frenchman, Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil, observed the first transit onboard a ship on the way to Mauritius (his measurements were useless), remained in the area of the Indian Ocean until the second transit which he failed to observe because of the cloud cover and returned to France after 10 years, his relatives having declared him dead and the Académie des Sciences ceasing to pay him, assuming the same. Charles Green, observing for the Royal Society from Tahiti with Captain Cook and Joseph Banks, died after falling ill in Jakarta (then Batavia) after he had made his observations.

The measurements of the first transit in 1761 were plagued by uncertainty, astronomers had anticipated that they would be able to measure the times of ingress and egress with high precision but found that even observers at the same location with the same equipment measured times differing by 10s of seconds. We often see sharp, static images of the sun but viewed live through a telescope the picture is quite different; particularly close to the horizon the view of the sun the sun boils and shimmers. This is a result of thermal convection in the earth’s atmosphere, and is known as “seeing”. It’s not something I’d appreciated until I’d looked at the sun myself through a telescope. This “seeing” is what caused the problems with measuring the transit times, the disk of Venus did not cross a sharp boundary into the face of the sun, it slides slowly into a turbulent mess.

The range of calculated earth-sun distances for the 1761 measurements was 77,100,000 to 98,700,000 miles which spans the modern value of 92,960,000 miles. This represents a 22% range. By 1769 astronomers had learned from their experience, and the central estimate for the earth-sun distance by Thomas Hornsby was 93,726,000 miles, a discrepancy of less than 1% compared to the modern value. The range of the 1769 measurements was 4,000,000 miles which is only 4% of the earth-sun distance.

By the time of the second transit there was a great deal of political and public interest in the project. Catherine the Great was very keen to see Russia play a full part in the transit observations, in England George III directly supported the transit voyages and other European monarchs were equally keen.

Chasing Venus is of the same theme as a number of books I have reviewed previously: The Measure of the Earth, The Measure of All Things, Map of a Nation, and The Great Arc. The first two of these are on the measurement of the size, and to a degree, the shape of the Earth. The first in Ecuador in 1735, the second in revolutionary France. The Great Arc and Map of a Nation are the stories of the mapping by triangulation of India and Great Britain. In these books it is the travel, and difficult conditions that are the central story. The scientific tasks involved are simply explained, although challenging to conduct with accuracy at the time they were made and technically complex in practice.

There is a small error in the book which caused me initial excitement, the first transit of Venus was observed in 1639 by Jeremiah Horrocks and William Crabtree, Horrocks being located in Hoole, Cheshire according to Wulf. Hoole, Cheshire is suburb of Chester about a mile from where I am typing this. Sadly, Wulf is wrong, Horrocks appears to have made his observations either at Carr House in Bretherton or Much Hoole (a neighbouring village) both in Lancashire and 50 miles from where I sit.

Perhaps unfairly I found this book a slightly repetitive list of difficult journeys conducted first in 1761, and then in 1769. It brought home to me the level of sacrifice for these early scientific missions, and indeed global trade, simply in the separation from ones family for extended periods but quite often in death.