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. 

 
 
 
 

Five ways in which the rest of the world can avoid the homelessness crisis plaguing the US

Housing for all. Image: Nicobobinus/Flickr/creative commons.

Homelessness is a growing problem in the UK, where the number of people sleeping rough has doubled since 2010, yet it is dwarfed by the scale of the issue in the US. More than 500,000 homeless were found across the US during just one night, compared to the UK’s 2017 count of 4,751. Changes in the definition of homelessness and flawed methodologies suggest that the true number for the US could be anywhere from 2.5 to 10.2 times greater.

Millions more live in overcrowded or slum housing, forced to choose between the damage that poor conditions do to their physical and mental health, and the street. All of the US’s housing issues – from foreclosures to evictions to poor conditions – hit communities of colour the hardest.

This is due to a legacy of discrimination, which continues to undercut any commitment to safe and decent housing for all residents, whether in the private or public sector. In my recent book, City of Segregation, I explain how the long, violent history of creating spaces for the white and privileged classes is embedded in a number of practices, which continue in US cities to this day.

Exporting inequality

As private developers and investors seek out urban land in major cities around the world to secure their fortunes, real estate patterns and practices developed within the US are increasingly being observed elsewhere.

In cities as diverse as London, Sydney and Durban, community groups which have been working for decades to improve their neighbourhoods languish with little public or private resource. Meanwhile, developers create spaces for foreign investors and new residents, who anticipate certain protections and privileges such as greater security, high quality amenities and neighbours with similar interests and backgrounds.

This is a driving force behind rising evictions and the criminalisation of homelessness, alongside gated communities, hostile architecture, “broken windows” policing with its focus on prosecuting activities such as graffiti or jaywalking and the growing privatisation of public spaces through regeneration.

But there is still time for other countries to choose a different path. The UK, in particular, can build on the legacies of the post-war political consensus that all residents should have access to quality housing, and its acknowledgement of institutional racism and some history of government anti-racist campaigning.

Both legacies should be improved, but a renewed commitment to a programme of housing and anti-racism are central to increasing equality, prosperity and well-being for all. Based on my research, I’ve come up with five steps which the UK and countries like it can follow, to ensure that future development reduces – rather than drives – homelessness and inequality.


1. Build social housing

Unlike the US, the UK acknowledges a right to a home, and within living memory provided it for a huge swathe of British society. Social housing – whether in the form of traditional council flats, cooperatives or community land trusts – provides a variety of housing types and keeps rents from rising too far beyond wages.

When social housing is widely available, it makes a huge difference to people who – for one reason or another, and often through no fault of their own – become homeless. With social housing to fall back on, homelessness is a temporary condition which can be safely resolved. Without it, homelessness can become a life-destroying downwards spiral.

2. Preserve and expand community assets

Severe segregation in the US stripped entire communities of access to quality food, jobs, education, green spaces, services, banks and loans. Poverty is endemic, and can easily tip into homelessness. While far from perfect, the UK’s post-war commitment to universal provision of services, such as education and health care, and building social housing across all neighbourhoods underpinned a surge in upward mobility.

This achievement should be salvaged from the damage done by Right To Buy – a policy which sold off social housing without replacing it – and austerity, which has prompted a sell-off of public assets and land, as well as the closure of childrens’ services, libraries and community centres.

3. Decommodify housing

A market geared towards building apartment blocks for the portfolios of investors who will never live in them cannot produce the kind of housing and neighbourhoods which residents need, much less at a price they can afford.

While London has been badly affected for some time, this trend is now spreading to other areas of the UK and Europe. Local and national governments must act to prevent global demand for housing as investments from driving prices beyond the reach of those who need real homes.

4. Build communities, not walls

Gates, bars, armed security and homeowner restrictions are all ugly traits of private housing developed within the US context of desperate inequality and racism. The UK has a long and vibrant tradition of community development, creating a supportive built environment and social infrastructure of schools, libraries and other municipal services for residents.

Community assets. Image: Helen K/Flickr/creative commons.

This kind of development, and the social mobility and growing equality it fosters, safeguards public health and safety – not big walls, barbed wire and security guards. The private rented sector in the UK should be regulated to bring it more in line with Europe, where tenants prosper with security of tenure and strong regulation of rents and rent increases.

5. Raise your voice

Those who are bearing the brunt of our current housing crisis must be at the centre of efforts to change it. From tenants’ associations and renters’ unions, to campaign groups such as Justice for Grenfell, it’s vital to support those voices advocating fairer housing rights.

This also means rejecting austerity’s constant cuts to public services, funding social support for physical and mental health and ensuring that homes are safe, decent and secure, to create a safety net for those who are working to improve their communities.

The Conversation

Andrea Gibbons, Researcher in Sustainable Housing and Urban Studies, University of Salford.

This article is republished from The Conversation under a Creative Commons license. Read the original article.