‘Three unique words’ map

A person looking out at a valley with text Wished/Contract/Ghosts

The What3words (W3W) smartphone app has divided the entire surface of the Earth into 57 trillion 3m x 3m squares. A unique three-word code for each square is generated by an algorithm in the app within the phone – no external communication is needed to do this. 

The algorithm creates combinations so that mispronounced words point to a position far from the intended location. For example, the app gives the location of the Rambler’s central office at Camelford House in Vauxhall as shift.meals.useful, while shift.miles.useful is in a railroad switching yard in Chicago. W3W argues that this is more robust than spoken alphanumerical coordinates, where digits could be transposed or omitted, and resulting errors would be hard to detect.

I am Chair of the Royal Institute of Navigation’s (RIN) technical committee. The RIN has no official position on W3W, or indeed on any other products or technologies, but we want to ensure that discussions are informed with accurate and reliable information. In the case of W3W some inaccurate comments had been made, notably that users need to download the app to be able to provide a W3W position, which is not the case.

Canalside, with the words: gradually, vase, written

The software has generated lively debate within the Royal Institute of Navigation (RIN). We recently visited the company’s head office in London to find out more, and especially how W3W is used by emergency services. I visited them with John Pottle, the director of the RIN, and we met Chris Sheldrick, the CEO. This was to get first-hand information on their business model, history and future plans. Some RIN members had expressed unease that a new, disruptive and potentially global addressing system was in the hands of a private entity – which is true – but this is case for other services such as Google maps.

Use in emergencies

Originally devised as a means to provide an address system to people in remote and impoverished areas, W3W is becoming more widely used in as it gets adopted by more companies and organisations. Premier Inn, for example, is now giving W3W addresses to guests and Ramblers groups are increasingly using it to steer walkers to the meeting point for walks.

W3W was never designed for emergency use, but has proved useful and has been widely adopted, but more by accident than by design. Contrary to some public comments, callers to emergency services do not need to download the app. Responders will text a link to the caller which connects them to a server, which obtains the caller’s position and generates the three-word code remotely in the server. Very little data needs to be transferred to or from the phone to do this. Navigation apps such as Navmii which use off-line maps will show a W3W position on their maps without needing a phone connection. The UK implementation of W3W uses Google Maps, which does require a data connection to display a map, but the W3W app will generate a three-word code even if the user has no phone signal or indeed no SIM.

An emergency call location system known as advanced mobile location (AML) is being implemented in the UK but is not yet available everywhere. This is built into recent mobile phone operating systems and automatically detects that 999 or 112 has been dialled, then switches on GPS and other location capabilities in the phone, and transmits a position without any intervention by the caller. Many agree that AML is the best solution for accurately locating the source of emergency calls, but w3w is a useful facility until AML is fully deployed.

A field with sheep and a gate, and the words: bags.sofas.rebirth

W3W versus grid references

The OS Locate app referred to by a reader in Walk (Your Say, Winter 2019) will generate OS grid references, but these have a granularity of 100m, compared with 3m for W3W. Consumer satellite navigation devices in the UK with an unobstructed view of the sky typically achieve an accuracy of 2m-5m, and devices entering the market in the next couple of years are likely to perform significantly better. Much of the time the difference in precision between W3W and OS grid references may not matter, but could be critical to pinpoint which side of an obstruction such as a motorway, railway line or river a caller is on, or in bad visibility.

The W3W app can of course be used routinely to help hiking companions find each other, with enough resolution to identify, for example, which door of the pub to use.

Unlike OS Locate, what3words provides no height information. The OS app does not state whether it reports heights with respect to the GPS mathematical model of the Earth, or mean sea level as used by OS maps. In the UK there can be a difference of tens of meters between uncorrected GPS heights and OS map contours.

Bob Cockshott is chair of the Royal Institute of Navigation’s Technical Committee and has been a member of the Ramblers for 20 years.


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