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Mobile Phone as an Emergency Beacon

November 13, 2019

How do you find a lost person who has no emergency location beacon? Typically, this person would be in difficulties, ill-equipped for the environment they were now in through bad luck, unpredicted weather, unfamiliar environment, poor judgement, or stupidity. The one item that can be relied upon to be in their possession is the ubiquitous mobile phone.


Network operators can furnish useful location information before the SAR operator gets off the ground.

The location of the serving cell to which the phone is currently connected, the sector and possibly an estimate as to distance from the tower can be approximated. The search can then commence in the area indicated by them.

Generally, DF systems use RF energy to derive a bearing and the amount of signal to indicate distance using specialist antenna arrays such as: Doppler, Interferometer, Null systems, Beam forming, or articulated Yagi. Accuracy of these technologies is not particularly good at greater distances, since the distance estimations are based on signal strength, and some sort of calibration of the transmitter is required for this to be reasonably accurate. A mobile phone is not a calibrated transmitter.

All modern cellular systems use encryption and authentication, plus frequency hopping and spread spectrum, making it virtually impossible to do anything as a third party.

Cellular phones need a network. Contrary to popular myth no transmission can start without first seeing a compatible network. When connected to the network, the phone is only communicating with one cell, the serving cell.

SAR worst case is an out of service phone: The subscriber can’t call or be called, and the Network operator can’t offer any location information.

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What is the solution to finding a phone in a no coverage situation?

Mount a mobile cell on an airborne platform, and we could then attract the phone to us and command it to transmit on a single frequency of our choice without frequency hopping or encryption. As previously discussed, traditional direction-finding systems use RF energy to derive a bearing and the amount of signal to indicate distance. This type of system must use specialist antenna arrays. The bearing accuracy of these technologies is not particularly good at greater distances, and since the distance estimations are based on signal strength, a calibrated transmitter is required. A mobile phone is not a calibrated transmission source.

ARTEMIS is an advanced location system using Cellular protocol to estimate the distance from aircraft to the mobile phone. Specialist antenna arrays are not required, just two ordinary antennas of the correct frequency response.

ARTEMIS communicates with the mobile using Cellular protocols, GSM, UMTS or LTE. Estimating the distance from the aircraft to the mobile phone employing a number of proprietary algorithms for GSM, UMTS and LTE, not signal strength. These methods give a predictable and accurate distance estimations (up to 35km). Using this method in conjunction with the aircraft position (GPS), an actual fix (Lat and Long) is calculated rather than just a bearing (although a bearing is also displayed).

Calls and texts to and from the mobile are also possible while displaying position. The system supports the location of multiple phones, which could include ground /sea assets, enabling a better understanding of the current situation. As the system calculates the phone location as a point on the map it is also possible to cue EO/IR sensors/lights etc. enabling searches at night or in reduced light/IMC conditions.

ARTEMIS has been specifically designed and configured to meet the extreme environments of helicopters in the SAR role.

ARTEMIS offers a simple but powerful user interface designed to be easily operated but offering modes of operations to suit every mission.

ARTEMIS can be easily integrated into an existing avionics rack, or temporarily fitted for a particular role. The user interface is accessed by any screen equipped with a web browser, on an existing flight computer screen or a free-standing laptop. Connection is by LAN cable or WiFi.

ARTEMIS employs unique Smith Myers distance estimation algorithms, dispensing with the need for specialist direction finding antenna arrays, using simple omni directional antennas.

ARTEMIS is available in a number of sizes, some suitable for UAV platforms, the smallest being 550g, with a significantly shorter range (2 to 3 km). Features and software are the same. ARTEMIS L is also IP 67 rated.

Smith Myers, innovative design of ARTEMIS has been recognised across a number of industries, culminating with a silver medal from The Royal Aeronautical Society. Artemis is used in the Norwegian AW101 All-Weather SAR Helicopter, arguably the most advanced SAR helicopter in the world. ARTEMIS is also used on fixed wing aircraft such as The BN Defender used by CAE Aviation Luxembourg, Europe’s largest ISR provider.

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