The What3Words (W3W) geocoding algorithm creates potential for confusing different nearby addresses, with potentially hazardous implications in emergency situations, according to a new simulation-based analysis of the location-identifying application.
W3W uses a geocoding algorithm to divide the surface of the globe into 3 metre squares, and assigns a unique three word address to every square on the planet - 57 trillion addresses. For example, 10 Downing Street is located at ///easy.fans.blast; Kensington Palace is ///lock.herds.gently; GMC London ///case.having.mugs; and BMA House ///able.bucked.fear.
The British startup company explains that street addresses aren't accurate enough to specify precise locations, such as building entrances, and don't exist for parks and many rural areas. W3W is available in over 50 languages and claims millions of users in 193 countries worldwide, as disparate as California State Parks, Ambulance Tasmania, and the Singapore Police Force.
Three Words to Send Emergency Services to an Exact Location
The company says the free app for iOS and Android "works offline – ideal for areas with unreliable data connection" and is available as a searchable online map. The app can geolocate a user and display their position as a three word address that can be relayed to an emergency services call handler. It should be easier and faster than searching latitude and longitude for someone in need of help.
The app has been recommended by numerous police forces in the UK and is also used by fire and rescue, ambulance services, and the UK coastguard.
However, the system has generated considerable controversy, not least for anecdotal reports of sending rescuers to the wrong location.
For the study, published in PLoS ONE , Dr Rudy Arthur PhD, senior lecturer in data science at the University of Exeter, formulated a model of address transmission by the W3W system and then used it to study the global prevalence of confusing addresses, and to assess confusing addresses that are close together. The model focussed on typographic errors and simple homophones to generate a list of potential error types relevant for transmission of W3W addresses.
Typing Errors and Homophones Are Common
- Typing errors: eg fog vs fig, calm vs clam.
- Homophones: their vs there.
- Incorrect word form: break vs broke.
- Autocorrect substitution: gunna vs gunman.
- Regional spelling variation: color vs colour.
- Boundary uncertainty: dog.start vs dogs.tart.
- Multi-word homophony: pink.start vs pinks.start.
- Word transpositions: dark.small.places vs small.dark.places.
Dr Arthur reported that most of the simulated W3W addresses had one or more word triples with which they could be confused – and up to a quarter had more than three. In addition, simulations suggested that the likelihood of a pair of confusable triplet word location identifiers was "far in excess" of the 1 in 2.5 million chance cited by W3W.
While these ambiguities could be resolved by transmitting multiple [adjacent] addresses, or spelling out the words, this would mean losing "the main advantage of W3W, simplicity", Dr Arthur said.
"High Potential for Ambiguity"
He acknowledged that W3W was "an interesting attempt at an addressing system that doesn't use alphanumeric codes". However, using words instead "has a high potential for ambiguity". Although alphanumeric codes have "similar potential for confusion", the longstanding phonetic alphabet [alfa bravo charlie delta etc] can reduce these, and may be much easier for non-native speakers, and less likely to be affected by accent and/or difficulties in pronunciation.
However, Dr Arthur admitted, "while showing that many confusable pairs exist, this work does not show that they will be confused". Nevertheless, he cautioned against widespread adoption of W3W, and reliance upon it by emergency services and other key agencies, especially in applications with a noisy communication channel between sender and receiver, until claims for ease of use and reliability had been "thoroughly examined and empirically compared with alternatives".
Emergency Callers Often Struggle to Communicate Location
In July, the Yorkshire Ambulance Service (YAS) and others backed a campaign by W3W to raise awareness of the app as "a simple way to communicate very precise locations" in an emergency. Asked to comment by Medscape News UK, YAS said, "The WhatWords app has been very useful in locating patients, particularly those in rural areas."
W3W said that over half (56%) of emergency services "receive daily calls from people who don't know exactly where they are or struggle to describe the location of an incident". Call handlers and dispatch teams often can't detect where people are automatically, and can't receive dropped pins, the campaign noted. Moreover, Ordnance Survey has reported that three-quarters of UK adults can't read a map.
Gill Pleming, service manager for the Welsh Ambulance Service, described W3W as "an invaluable addition to our emergency response toolkit", saying it saved time and resources in time critical situations.
Medscape News UK has asked What3Words for comment on the study findings. The company, though, has previously addressed the potential for confusable word combinations. In a 2021 blog, it referred to its own research which suggested that people confuse plurals only about 5% of the time when hearing them read out loud. It acknowledged that homophones were commonplace in the English language but maintained that "the probabilities of these resulting in a real-life confusion are very low".