When you call 999, your phone can automatically determine your location using wifi and GPS positioning data, then text it to the emergency services.

Advanced Mobile Location (AML) – The gory details

Written by Haydn Williams

Summary – When you call 999, your phone can automatically determine your location using wifi and GPS positioning data, then text it to the emergency services. In 90% of cases in a 2016 report, the location accuracy was 50m or less (compared to 2.8km for a mobile phone mast). AML has the advantage that no 3G/4G data connection is required, and this all happens in about 30 seconds without the user even knowing. As long as the phone can make a call in the first place, and then send a text message, it works. There’s an explanation of the full process here. Phones running Android version 9 (Gingerbread) onwards are already using this function. iPhone users are covered from iOS 11.3 onwards.

Difference between cell-mast location and wifi/GPS location. © EENA / BT
Difference between cell-mast location and wifi/GPS location.


How it Works – When 999 (or 112) is dialled on an AML-enabled handset, the operating system will first check the battery level. If the charge level is critical, nothing happens (to save the battery for a call). If there is sufficient charge, then wifi and GPS will be enabled, and used to determine the handset’s location if possible. The accuracy will vary, depending on a number of factors such as surrounding wifi networks (not many on top of a hill!) and whether the handset uses just GPS, or GPS along with GLONASS, Galileo, etc. Mobile data is also switched on, and the handset will contact an NTP server to obtain an accurate and exact current time. An SMS text message will then be sent to the emergency services, containing the location and time details. Details can optionally be sent over a data connection via HTTPS if 3G/4G is available. Wifi, GPS and mobile data will then be switched back off again. All of this happens transparently without the user being made aware; information gathering usually takes 20 seconds, and the transmission by text message another 10 seconds or so. If you make another 999 or 112 call, then the process repeats.

History – Ofcom were looking at the issue of mobile phone location back in 2004, when they introduced a requirement for enhanced location services on mobile phones, in conjunction with mobile operators.

By 2011, the minimum criteria set out by Ofcom for mobile operators to provide during emergency calls was:”using a Mobile Network, the Caller Location Information must include, at least, the Cell Identification of the cell from which the call is being made” [Sec. 4.2 and 4.34(b)]. Cell identification can give areas of up to 20km2 in rural locations, so Ofcom commissioned BT to investigate potential improvements to this system [Sec. 1.8]. As part of that work BT built an Android app which recognised the user dialling 999 or 112, and switched on wifi and GPS to identify their location. Despite some challenges, the technology worked well as a proof of principle [p.99]. In 2013, Ofcom held a consultation about location information for emergency calls from mobile phones. After responses from various parties, the outcome in 2014 was that no action would be taken by Ofcom. This was because, in the time between consultation and conclusion, BT had continued with their earlier work. This included presenting in detail at the 2014 EENA conference.

In February 2015, the new system got more exposure via a post and case study on the European Emergency Number Association (EENA) website, by which time it had also gained the name Advanced Mobile Location (AML). The case study states that, at that time, AML was a collaboration between BT, EE and the handset manufacturer HTC. By the end of 2015, Sony, Alcatel, and Samsung were also getting in on the act, as were O2. In July 2016, Google announced that AML would be included in all versions of Android from Gingerbread onwards. In August 2017, the EENA lobbied Apple to include AML in the iOS operating system on the iPhone, and in January 2018 it was confirmed that it would be included in version 11.3 of iOS. While the technology works well in the UK, the EENA released a rather bizarre spoof interview to try and highlight the relatively poor implementation in other countries. In 2017, the European Commission HELP112 project concluded that across Europe “the main recommendation is the deployment of handset based location solutions […]. A solution like AML […] shall be the first step.

The EENA has a page dedicated to AML, which is here: http://www.eena.org/pages/aml#.WoAm1GacYsl

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