From coconuts to GPS: A brief history of navigation

It's good, but it's no coconut. Image: Getty.

If I ask Google:

It helpfully displays a map of where I used to live:

Google is very good at knowing where I used to be. My phone is constantly keeping track of my location and uploading it to their servers. It has stored my location 579,088 times since September 2013.

Each location stored looks like this:

{
 “timestampMs” : “1431497952458”,
 “latitudeE7” : 513453840,
 “longitudeE7” : -1015043,
 “accuracy” : 27,
}

This isn’t that easy to read. The E7 is an instruction to divide by 10,000,000, to reach a traditional set of latitude and longitude coordinates. “timestampMs” tells us that wherever 51.345384° N -0.1015043° E is, I was there at 1,4314,9795,2458 milliseconds after midnight on the 1st January 1970.

Even knowing what each of those numbers represent, we need to do some work to get these back into a human context. By putting the numbers through mapping software I can find out that “51.345384°, -0.1015043°” is Purley Oaks station in South Croydon. By running the timestamp through a conversion system, I can see I was apparently there at 7:19:12 AM on the 13 May 2015. This makes perfect sense, it was part of my daily commute at the time — I’d have been there most days at that time.

Most of the data stored about my location places me somewhere I lived or somewhere I worked. Just occasionally, I do something interesting and the database gets to store whole new sets of coordinates. If I take several years of this data I can produce maps of the sums of my positions over time:

This is my life as latitude and longitude, expressed in a way that can be easily understood by a human. Where I’ve spent any amount of time the map is redder; journeys appear as snail trails across the country.

Google’s algorithms don’t require any of this “coloured in map” nonsense. After a few weeks, your Android phone can make a reasonable guess at where your work and home are, based on where you spend most of your days and where you spend most of your nights. It doesn’t need to ask — that would be intrusive.

To determine a position on a globe while inconveniently being stuck on that globe you need fixed external references. Fortunately the universe is full of these.

One of simpler means sailors used to work out their relative position from destination was a kamal – a board with a hole in the middle. By putting a string through the hole and holding one end of the string in your teeth, you position the lower edge of the board on the horizon and move it further away until the board obscures your target star (typically Polaris — if visible).

An enthusiastic Wikipedia editor showing how the kamal works. Image: Markus Nielbock/Wikimedia Commons.

The length of the string between your teeth and the board tells you your latitude. By knowing the length of string required for certain ports, you could adjust course to navigate to a place. Using nothing more than your teeth, a string, a plank of wood, a star – and the horizon.

In Polynesia (lacking in a helpful pole star) titiro ‘ētū – “star peekers” – made of nothing but coconuts and seawater were used to navigate to specific islands. To use these, you cut off the top of the coconut and make a ring of holes around the base. You then make a hole near the top for the target star and fill it with water up to the holes (with coconut oil to maintain surface tension). You look through the device at the star at its highest point; if the water inside the device is flat, you are on the same latitude as your destination. The stars will guide you with the simplest of tools, if you know how to use them.


Progression east-west (longitude) can be understood if you know the difference between high-noon on a clock set at a fixed location (Greenwich) and a clock set at the current location. Each hour difference represents 15° of travel longitudinally (1/24 of 360°). Simple enough, if you have a clock that can keep time on the ocean – but that was a complicated problem to solve. Before that, all sailors could really do is line up on the right latitude and go for it.

To make use of more markers than the sun and North Star, you could use nautical almanacs and sextants. These almanacs were essentially large lists of what celestial objects should appear at certain points of the sky, and at what time they can be expected to do so. By using the sextant to compare predicted appearances to actual locations, you can determine the distance to fixed positions.

The Global Positioning System (GPS) has mostly replaced the need for these tables. Reliable but not available on-demand stars have been replaced by artificial celestial bodies that spend their whole lives yelling about where they are and what time they think it is. By comparing signals from several different satellites to the time your GPS device thinks it is, you can triangulate your position on the earth within a few meters.

Few mobile phones contain true GPS: mostly they use aGPS or WPS. aGPS uses the resources of the mobile network to speed up reconciliation based on fragmented signals, but WPS (Wireless Positioning System) is something different altogether. It takes advantage of the fact that we littered our world (especially urban areas, where GPS struggles) with millions of radio location beacons, in the form of Wi-Fi access points.

While the vans with the weird cameras were taking pictures of every road in the world, they were also mapping the radio landscape we have made: each house with a Wi-Fi access point, broadcasting a unique identifier. By mapping these to a true GPS reading, location services can provide a guide to any device with a wifi chip. If you read Device #1053443 with 50 per cent strength and Device #10232321 with 74 per cent strength and Device #24324239 with 60 per cent strength, the chances are you are “here” — the most likely place where those signals converge at that strength.

These vans are no longer necessary: while walking around your phone will pick up on any new or unknown access points. With sufficient logs of these devices, their location can be deduced by comparison to known devices and used for future navigation. As well as recording our every step, our phones are automated radio cartographers. This is still ultimately working on similar principles to the nautical almanac and sextant, it just has a much larger look-up table and uses thousands of man-made stars to light the way.

As navigation has become much easier there is also the risk of becoming too dependent on what might turn out to be fragile technology. The US Navy is currently re-introducing celestial navigation training. so that its sailors can figure out where they are in the event of an attack on the GPS system. After the apocalypse, we might find ourselves getting around by holding a bricked phone up to the horizon and measuring the length of the headphone cord to our teeth. 

 
 
 
 

The Delhi Metro: How do you build a transport system for 26m people?

Indraprastha station in 2006. Image: Getty.

“Thou hath not played rugby until thou hath tried to get onto a Delhi Metro in rush hour,” a wise Yogi once said.

If you’ve never been on New Delhi’s Metro, your mind might conjure up the the conventional image of Indian trains: tawdry carriages, buckets of sweat, people hanging out of windows and the odd holy cow wandering around for good measure.

Well, no. The Delhi Metro is actually one of the most marvellously sophisticated, affordable, timely, and practical public transportation systems out there. On a 45C day in the Indian summer, many a traveller has shed tears of joy on entering the spacious, air-conditioned carriages.

Above ground, Delhi is a sprawling metropolis of the scariest kind: 26m people, three times the population of London, churn and grind through Delhi itself.

The National Capital Region, an area which includes Delhi and its surrounding satellite cities – now victim of its never-ending urban sprawl – has an estimated population of almost 50m. So how do you tie such a huge population together?

The map; click to expand. Image: Delhi Metro Rail.

Motorised vehicles won’t do it alone. For one, air pollution is a horrific problem in Delhi, as it is across India. Last November, the government declared a state of emergency when the Indian capital was engulfed by a toxic, choking fog so thick that you could barely see several metres in front of you, drawing allusions to the great Victorian fogs in London.

Then there’s Delhi’s famous traffic. Twenty-five years ago, the travel writer William Dalrymple observed that you could reduce the Delhi’s road laws to one simple idea: the largest vehicle always had the right of way. The traffic has tamed somewhat in the 21st century, but the number of vehicles has multiplied again and again, and it’s not uncommon for people to be stuck in four-hour traffic jams when they try to traverse the mighty city.

Enter the Delhi Metro – a huge network of 164 over- and underground stations – and by any account, a titan of civil engineering and administration.

The numbers are simply colossal. Every day the metro serves on average almost 3m people. Annually, it carries around 1bn.

In a country where intercity trains still turn up a day late, the Delhi Metro is extraordinarily timely. On the major lines, trains will come every several minutes. The trains are extraordinary speedy, and you’ll reach your destination in a fraction of the time it would take for you to drive the distance.

The minimum fare is 10 rupees (12p); the maximum fare, to and from the airport, is 50 (60p).

The evolution of the metro. Image: Terramorphus/Wikimedia Commons.

Construction of the metro system began in 1998, with the first section completed in late 2002. Keen to avoid the catastrophic corruption and bureaucratic mismanagement which plagued eastern city of the Kolkata Metro, developers took advice from Hong Kong’s high-tech system There have been several stages of development to add extra lines; more is planned. By 2020, it is hoped that the 135 miles of line will have increased to over 300.  

One thing quite striking about the metro is its women’s only carriages at the rear and the front of the train, marked by pink signs. Sexual assault and harassment has been a horrific problem on Delhi’s transport systems. Women can of course go anywhere on the train – but men who violate the carriage system will have to deal with the scathing anger of the entire pink carriage.


One of the under-discussed impacts of widespread and well-used public transportation systems is their propensity to break down social and class barriers over time. As the London Tube began to be used more and more in early 20th century London, people from completely different walks of life and classes began to brush shoulders and share the same air.

The story is similar in Delhi. The necessity of the metro helps to break down old caste and class divisions. Of course, many elite Delhiites would not be seen dead on the metro, and choose their private chauffeur over brushing shoulders with the common man. But slowly and surely, the times are a changing.

What’s more, the Delhi Metro system is one of the greenest around. Six years ago, the Metro was the first railway system in the world to be awarded carbon credits from the United Nations for helping to reduce pollution in the capital by an estimated 640,000 tonnes every year.  

All praises sung and said, however, at peak times it’s less mind the gap and more mind your ribs – as a fifth of humanity seems to try to get on and off the train at once.

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