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Tracking & Locating Devices
Apple AirTags, Car Keys and more
Source image: https://unsplash.com/photos/a-cell-phone-sitting-on-top-of-a-moss-covered-ground-ReQq6kUYjLI
Modern technology has made it relatively easy to track the location of
people or property for safety, security or other purposes. Trackers can
be used to locate children, pets, your mobile phone, computer, baggage,
products in transit, machinery, cars, boats, planes or just about any other
movable object.
By Dr David Maddison, VK3DSM
T
racking devices operate over various distances, from short to long
ranges. Some can provide an absolute
position fix, such as latitude and longitude coordinates, while others give
a relative position, such as an approximate distance and direction from your
current location.
Modern GPS/GNSS receivers are
small enough and have low enough
power consumption to make them
practical for use in portable devices.
More recent technologies used for
tracking include ‘multilateration’
(triangulation) with radio beams and
‘ultra-wideband’ (UWB) chips.
This article will cover tracking
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techniques, technologies and methods
and then give examples of common or
interesting tracking devices.
As mentioned in our June 2024 article on Privacy Phones (siliconchip.au/
Article/16280), it is generally possible
for anyone carrying a mobile phone
to be tracked even without their permission.
Tracking techniques and
technologies
Satellite positioning systems,
including GPS, Galileo, BeiDou and
GLONASS, are collectively known
as GNSS (global navigation satellite
systems). Many trackers will locate
Australia's electronics magazine
themselves using GNSS and then
transmit that location via WiFi, Bluetooth, 4G/5G or radio.
Non-GNSS tracking devices typically emit a radio signal, either via
Bluetooth, UWB or WiFi, which is
then processed to extract positional
data such as via one of the techniques
described below: AoA, Multilateration, NFER, ToA, TdoA or ToF. One
advantage of those systems is that they
can work in places where GNSS signals are too weak or blocked, such as
indoors or underground.
Angle of arrival (AoA)
The direction of a transmitter can
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be determined by measuring the AoA
of a radio signal using an antenna
array and measuring the phase shift
of a received signal between each of
multiple antennas – see Fig.1. A second angle measurement from a second
antenna array allows the location to be
established at the intersection of the
two directional vectors.
Multilateration (see below) needs
a minimum of three sensors, while
this technique requires two. However,
using more sensors generally provides
better accuracy.
Bluetooth
This is a popular short-range wireless communications protocol for
functions such as connecting wireless headsets to a phone or computer,
connecting a phone to a car, printing,
remote control etc. It has other applications, including locating and tracking objects. Its operating range extends
to about 10m for basic Bluetooth and
up to about 240m for Bluetooth 5.3
(depending on the amount of clutter).
Bluetooth Low Energy (BLE) beacons are commonly used for tracking.
One method of localisation for these
beacons is multilateration, using three
fixed beacons or ‘anchors’ to measure
the distance to a movable device.
Even with a single device, the distance can be roughly determined by
measuring signal strength. A Bluetooth Distance Measurement API uses
the Bluetooth RSSI (Received Signal
Strength Indicator); the direction can
be determined using antennas on multiple devices.
Fig.1: the angle-of-arrival locating method using
an antenna array, such as a WiFi router with
multiple antennas. A second router is needed
to establish the position (one just gives you an
angle).
Fig.2: the principle of multilateration using
three fixed devices at the centre of circles with
radiuses r1, r2 and r3; the tracked device is at
the point (x,y).
Multilateration
This is also known as hyperbolic
positioning or trilateration; it is the
process of determining the position
of an object by measuring the distance between three or more known
locations and one unknown location
– see Fig.2. The distance may be established by the time difference of arrival
(TdoA) of radio signals, relative signal
strength or other means.
Near-field electromagnetic ranging
Near-field electromagnetic ranging
(NFER) is an emerging ranging technique not yet commonly used for tracking. A radio transmission’s ‘near field’
is the electromagnetic field close to the
antenna (see Fig.3). Its properties differ
from the electromagnetic field further
away, the ‘far field’.
Fig.3: radio transmissions differ in how they behave in ‘near fields’ (close
to the transmitter) & ‘far fields’ (further away). Original author: Goran M
Djuknic
siliconchip.com.au
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August 2024 13
Close to a small antenna or emitter,
in the near field, the electric (E) and
magnetic (H) components of an electromagnetic (EM) wave are up to 90°
out of phase. In the far field, the pattern
of electromagnetic radiation is more
conventional. The phase difference
between the EM wave’s electric and
magnetic field components in the far
field is zero; they are in phase.
Between those two extremes, the
phase difference is less than 90°, so
if the phase difference is measured, it
can indicate distance. NFER uses frequencies below about 30MHz.
As an example, for a 1MHz signal,
Fig.4: the phase versus range relationships near an electric dipole. The phase
angle (labelled “Phase Delta”) can be used to determine the distance in terms of
wavelength. Original source: www.researchgate.net/publication/276919686
Fig.5: indoor WiFi positioning in an office environment using three routers
with Received Signal Strength Indicators (RSSI). Original source: https://
github.com/sankalpchauhan-me/
IndoorPositioning
Fig.6: how time-of-flight (ToF) is calculated in principle. δ is the delay in
response from the target device, T_P is the signal propagation time, T_ACK
is the time needed for acknowledgement and the ToF used in the calculated
distance is T_MEASURED. Original source: https://w.wiki/AMEk
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the phase difference between the electric and magnetic field varies from
75° to 25° over the more linear region
between 30m and 60m from the source
(see Fig.4). With a delta of 50° over
30m, if the phase different were measured with a 1° accuracy, that would
give a resolution of 1/50th of 30m, ie,
around 60cm.
NFER operates within about half a
wavelength of the signal used. A 1MHz
signal has a wavelength of 300m, so
a range up to about 150m could be
measured.
NFER is suitable for indoor use
where GPS signals can’t be received
(for example). One disadvantage
is that, due to the low frequencies
required, efficient antennas are large.
Possible solutions include fractal
antennas, loop antennas or ferrite rod
antennas (as used in small radios).
US patent 2014/0062792A1
describes a way to use commercial
AM broadcast signals as ‘signals of
opportunity’ for NFER. Usually, they
will be in the far field. Still, when
such signals interact with structures
like power lines, they can resonate
within them, introducing near-field
components as though that structure
was an emitting antenna and enabling
the signal to be used for NFER.
For more on near fields and far
fields, see these videos:
● “EEVblog #1273 - EMC Near Field
vs Far Field Explained” (https://youtu.
be/lYmfVMWbIHQ)
● “EEVblog #1178 - Build a $10
DIY EMC Probe” (https://youtu.
be/2xy3Hm1_ZqI)
● “#234: Basics of Near Field RF
Probes | E-Field & H-Field | How-to
use” (https://youtu.be/ctynv2klT6Q)
RSSI Fingerprinting
Received Signal Strength Indicator (RSSI) Fingerprinting is a positioning method using WiFi where a
database is created and constantly
updated to record the locations and
signal strengths of many WiFi access
points from various known positions.
This enables an unknown location to
be quickly determined by comparing
the WiFi signal strengths to signatures
in the database, with a median accuracy of 0.6m.
RSSI Multilateration
Received Signal Strength Indicator Multilateration uses the relative
strengths of signals as a proxy for the
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distance between devices. An example
of this method applied to WiFi routers
is shown in Fig.5.
Time of arrival (ToA)
While not tracking techniques, ToA
& TDoA (time difference of arrival) are
used in other techniques described
here. ToA is defined as the absolute
time when a radio signal emanating
from a transmitter reaches a remote
receiver. TDoA is the difference
between ToAs.
Time of flight (ToF)
Time of flight (ToF) is a WiFi-based
position measurement technique,
although the principle can be applied
to other types of signals. It involves
measuring the time taken for a radio
signal to travel (at the speed of light)
between a measuring station (in this
case, a WiFi access point) and a target device (eg, a smartphone) – see
Fig.6. The time taken to return is also
measured, allowing for a delay due to
response time.
The distance between devices can
be calculated, and in conjunction
with the time taken to other measuring stations, the location can be
determined. The system is accurate,
but devices must be synchronised to
a master clock.
Ultra-wideband (UWB)
UWB was briefly mentioned in our
June 2024 article on Privacy Phones
(siliconchip.au/Article/16280). This
technology is incorporated into various devices, including some iPhones
and certain Samsung and Google Pixel
model phones (more on that later).
UWB is a short-range radio protocol that operates between 3.1GHz and
10.4GHz. Radio energy is sent over a
very wide bandwidth, around 500MHz
or more, to allow the transmission of
a relatively large amount of energy
without exceeding regulatory limits
for certain frequency bands or causing
interference (see Fig.7). UWB utilises
extremely short pulses of one or two
nanoseconds.
Positioning using UWB is capable
of very high accuracy, with errors
as little as 10-50cm or even down to
centimetre-level accuracy (see “Athlete trackers” below).
UWB positioning or tracking systems ideally utilise three fixed receivers or anchors. Techniques such as
ToA, ToF or TDoA are used to establish
siliconchip.com.au
Fig.7: the frequency range and spectral power density of UWB compared with
other radio technologies. Source: www.rtsmartdata.com/technology/uwb
Fig.8: one variation of the Pulse Position Modulation (PPM) scheme used in UWB
communications. Source: www.rescueswag.com.au/products/rescueme-plb1
the distance between the UWB tag or
device and the receivers; the position
of the receiver is then established by
multilateration.
Unlike conventional radio, in which
information is transmitted via variations in frequency, phase or power,
with UWB, information is encoded
as pulses with specific time shifts
in a scheme known as Pulse Position Modulation (PPM) – see Fig.8.
UWB can transmit data at a high rate
(~100Mbit/s), with transmissions over
1Gbit/s having been demonstrated.
UWB is relatively energy-efficient
compared to other methods, and signals can pass through many obstacles,
including certain types of walls and
people in crowds.
Information sent from a UWB device
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usually contains its ID, ToF and timestamp data. UWB is governed by the
IEEE 802.15.4a/z standard.
UWB chips are fitted to the following devices:
• the Apple iPhone 11 and later,
excluding the iPhone SE (2nd and 3rd
generation)
• the Apple Watch Series 6 and later
• some other Apple devices
• various Samsung Galaxy models (including the Galaxy Buds Pro 2)
• the Google Pixel 8 (and some
other phones from Google)
• the Xiaomi MIX4
• the Motorola Edge 50
Some devices, such as the iPhones
with UWB, always have power to the
UWB chip even when the phone is ‘off’
so it can be used to find them.
August 2024 15
Wireless LAN (local area network)
WLAN/WiFi can be used for location and tracking.
Google uses publicly broadcast
data from WiFi routers that have been
scanned as they drive around in their
Street View vehicles. Their locations
are recorded (siliconchip.au/link/
ab9n) to enhance the accuracy and
speed of location in conjunction with
GPS (or to provide location even without GPS). This is used by any tracking app or hardware that uses Google
Location Services.
In smaller areas with access to a
WiFi network, devices can be located
using techniques such as RSSI Multilateration, RSSI Fingerprinting, ToF
and AoA.
Examples of tracking devices
Here are some example of commonly found tracking devices, listed
in alphabetical order. Note that this is
not meant to be a comprehensive list.
Aircraft tracking
Commercial and many other aircraft
are routinely tracked via a variety of
methods, including Aircraft Communications Addressing and Reporting
System (ACARS), Automatic Dependent Surveillance–Broadcast (ADSB) and FANS (Future Air Navigation
System).
ACARS communicates aircraft
events, including equipment and sensor status, via VHF and ground stations when near land (line-of-sight,
within about 370km) or via satellite
receivers for almost global coverage.
ACARS does not usually send position
coordinates but does send speed and
altitude.
ADS-B broadcasts an aircraft’s
callsign, position, altitude, velocity and other data twice per second.
That information is sent to air traffic controllers via ground stations or
satellites. Positional information is
obtained via GNSS.
Air Services Australia operates 61
ground stations for ADS-B. ADS-B is
mandatory in Australia for aircraft flying under instrument flight rules (IFR);
other countries have similar rules.
FANS is a system that provides
a data link between an aircraft and
aircraft traffic controllers, including
information concerning air traffic control clearances, pilot requests and position reporting. Communication is via
ground stations or satellite.
In 1995, a Qantas Boeing 747-400
(VH-OJQ) became the first aircraft to
use the Rolls-Royce FANS-1 package,
and Air New Zealand soon followed
with a package from General Electric.
Ankle bracelets
Courts order police to fit some criminals or suspects with a GPS ankle (or
wrist) bracelet for tracking them. These
can be used to restrict them to a particular zone (such as a home) or prevent
them from entering designated prohibited areas (such as where a victim
might live or work, airports, schools,
shopping centres etc). Alerts for violations are issued via the mobile phone
network.
These devices are waterproof, are
designed to detect tampering and will
periodically ‘check in’, generating an
Fig.9: internal and external views of an ElmoTech TRXL-830 ankle
monitor. Source: https://fccid.io/LSQ-TRXL-830/Internal-Photos/InternalPhotos-1338485.pdf
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alert if they are not functioning. As
the ankle monitor is offered as a ‘service’ to the recipient to allow some
freedom of movement, tampering is
regarded as a very serious matter and
will likely result in them being sent to
jail instead of having a small amount
of freedom.
Similar tracking devices can also be
used for people with mental impairments (eg, dementia) who may wander
away from institutional care facilities.
These devices can determine their
location via GPS, LBS (location-based
service, using mobile phone towers)
or indoor beacons using BLE when no
GPS or LBS signal is available.
One example is the ElmoTech
TRXL-830 (see Fig.9), designed to
enforce curfews. It has a receiver unit
that logs the presence or absence of a
‘client’ wearing one of these devices
and compares that with a stored
schedule of curfew hours the person has to conform to. If they are not
present, the receiver unit reports the
violation.
Bracelets with alcohol monitoring
The SCRAM Continuous Alcohol
Monitoring (CAM) bracelet (Fig.10;
siliconchip.au/link/abwj) is for certain
classes of criminals, such as habitual
drunk drivers or domestic violence
offenders. It samples the wearer’s
sweat for alcohol every 30 minutes and
reports the result. Alcohol in sweat is
detected with an electrochemical fuel
cell. The bracelet must be worn in contact with the skin.
The SCRAM CAM does not include
tracking but can be used in conjunction
Fig.10: the SCRAM Continuous
Alcohol Monitoring (CAM)
bracelet detects the wearer’s blood
alcohol level via their sweat.
Source: https://go.scramsystems.
com/l/149911/2016-05-02/
tmlc/149911/1614372926rk0W3lb1/
scram_cam_product_brochure.pdf
siliconchip.com.au
with a tracking bracelet on the other
ankle.
Apple’s AirTag
T h e A i r Ta g
(shown here and
in Fig.11) is a
small disc-like
token designed to
find and track keys,
luggage, computers, cars and any other
object they are attached to, including
people. AirTags use the proprietary
Apple “Find My” network, a crowdsourced mesh network that uses an
estimated one billion Apple devices.
It requires an iCloud account and uses
both Bluetooth and ultra-wideband
(UWB) technology.
The AirTag transmits a Bluetooth
‘beacon signal’ that is anonymously
received and retransmitted by other
Apple devices without alerting the
other device’s owner. iPhone 11 or
later users can also utilise the phone’s
U1 UWB chip (or U2 in the iPhone 15
and later) to locate the AirTag more
precisely.
The U1 has an approximate range of
20m, while the U2 has a range of up
to 60m, although estimates vary and it
depends on conditions. Some reports
claim AirTags can be detected at up to
250m outdoors. Despite the relatively
short ranges, you or your AirTag are
never likely to be far from an iPhone
in an urban area.
Some people have mailed packages
with AirTags to follow their route and
have had numerous ‘pings’ at airports,
warehouses and similar facilities.
Details on the impressive internals
Fig.13: a Playertek GPS device weighing 42g (top right) with a screen showing
the Playertek athlete monitoring tracker software. It depicts various parameters
and a heat map to show the location of athletes on the field. Source: https://
performbetter.co.uk/products/playertek
of the AirTag can be seen at https://
adamcatley.com/AirTag
Athlete trackers
Athletes’ activities can be monitored by GPS or UWB (ultra-wideband)
tracking devices worn within their
clothing, with the goal of improving
performance. The Playertek (Fig.13) is
an example of an athlete tracker that
uses GPS.
In the USA, the National Football
League (NFL) uses UWB trackers from
Zebra Technologies (www.zebra.com)
to monitor athletes and the ball. The
data collected includes the ball altitude, velocity, rotation, player speed,
passing rates, rushing attempt in yards,
pass completion, receiver separation
and more. They call this “Next Gen
Fig.11: the internals of an Apple AirTag (both sides). Onboard devices include
the Bosch Sensortec BMA28x 3-axis accelerometer, Apple U1 ultra-wideband
transceiver, Nordic Semiconductor nRF52832 Bluetooth low-energy SoC w/NFC
controller and various memory, audio and power supply components.
Source: www.ifixit.com/News/50145/airtag-teardown-part-one-yeah-this-tracks
(CC-BY-NC-SA)
siliconchip.com.au
Australia's electronics magazine
Stats”; see https://nextgenstats.nfl.
com/glossary
Each NFL stadium has 20-30 UWB
receivers, two or three trackers in each
player’s shoulder pads (to ensure better tracking when close to the ground),
trackers on officials and other items.
They collect around 1000 data points
per second with centimetre accuracy.
A total of around 250 trackers are
used for each game. A game can be
replayed in animated form in various
apps using the data (see siliconchip.
au/link/abx1).
Boats
Trackers for boats use the mobile
phone network or NB-IoT networks
close to shore, or a satellite service if
further out to sea (see Fig.12). Some
Fig.12: the Keep Track G120 Cellular
and Satellite GPS Tracker showing the
optional Iridium satellite module. It
can be used to track other assets apart
from boats. Source: Keep Track GPS
– siliconchip.au/link/abx2
August 2024 17
use both mobile and satellite links.
NB-IoT stands for ‘narrowband Internet of Things’ and is part of the mobile
network. Telstra’s NB-IoT coverage is
shown at siliconchip.au/link/abwk
Child trackers
Various child-tracking devices are
available. These are similar to devices
used for tracking adults but with the
style and functions tailored for children and their carers.
The Jiobit (www.jiobit.com) is a
highly-rated pendant-type device for
tracking children, but it is not supported in Australia. There are many
watch-style devices, some of which are
also suitable for adults. For example,
the Apple Watch SE is not designed
to track children but can be set up for
such use.
Two other examples (of many)
include the Kids Buddy Watch (see
siliconchip.au/link/abwl) and the
Garmin Bounce (siliconchip.au/link/
abwm) – see Fig.14. JB HiFi sells a
range of these devices, as shown at
siliconchip.au/link/abwn
Cube Shadow
The Cube Shadow (https://
cubetracker.com/) is a subscription
GPS tracker device and service that
connects via the mobile phone network. It is advertised for tracking vehicles, assets, fleets, the elderly and pets.
Although it is advertised as a global
service, the website states, “We currently do not offer shipping outside
the USA”.
Chipolo ONE Spot and CARD Spot
These AirTag alternatives work with
Google Find My Device (see Fig.15),
although they do not support UWB.
See siliconchip.au/link/abwo
Digital Car Keys
This type of virtual car key is powered by a smartphone or watch (Fig.16).
While not a tracker, it uses similar
technologies, including UWB. The
The misuse of trackers and the Tracker Detect app
Unfortunately, criminals have been
known to use tracking devices to stalk,
harass and track victims. Apart from
the Tracker Detect app, there is no
universal or practical way to detect or
disable them. Blocking GPS or phone
signals is illegal, so if you think you
are being stalked, contact your local
police.
Apple AirTags have been alleged to
be misused in this way, although no
doubt others have been too.
If you have an Apple device with
iOS 14.5 or later, it will alert you to the
presence of an AirTag that is not yours
and is moving with you. For further
details on that, see siliconchip.au/
link/abwv
You can detect the presence of
Apple AirTags using an Android
phone by using a free Apple app
called Tracker Detect. If an AirTag
has been tracking you for more than
ten minutes, the App will allow you
to play a sound on the AirTag to help
you find it. Android versions since
v6.0 (basically any modern version)
can also provide alerts for unknown
trackers; see siliconchip.au/link/
abww
What about GPS trackers that
transmit location data via the mobile An unknown tracker alert from a
phone network? Presumably, devices recent version of Android. Source:
that detect mobile phone activity can https://support.google.com/android/
detect such trackers. We came across answer/13658562?hl=en
two covert mobile detector devices: the PocketHound (siliconchip.au/link/
abwx) and the WG Portable Mobile Phone Detector (siliconchip.au/link/abwy).
If an active tracker does not use the mobile network, it would be difficult to
detect, especially if the radio link uses spread spectrum techniques or extremely
low power transmission like LoRa.
For further information, see the article at siliconchip.au/link/abwz and the
video titled “How Apple AirTags are being used by criminals” at https://youtu.
be/OfXyRUwvQ8Q
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Fig.14: a Garmin Bounce tracking
watch for children, with a screen
showing the child’s location.
Source: www.garmin.com/en-AU/
p/714945#overview
Fig.15: a Chipolo ONE point tracking
device in use. We would keep the tag
inside the suitcase rather than on
the outside (as long as the case is not
metallic). Source: https://chipolo.net/
en/products/chipolo-one-point
siliconchip.com.au
Car Connectivity Consortium (CCC)
maintains the specification. Car manufacturers who support the standard
include AITO, BMW, BYD, Genesis,
Gogoro, Hyundai, Kia, Lotus, Mercedes
Benz, MINI, RAM, Škoda & Volvo.
The keys are stored in mobile digital
wallets such as Google Wallet, Samsung Wallet, Huawei Wallet and Apple
Wallet for iOS and watchOS. Communication occurs via NFC (near-field
communication) at very short ranges
or UWB at longer ranges.
Emergency locator transmitter
(ELT)
ELTs signal aircraft distress. They
operate similarly to EPIRBs and transmit on 406MHz and 121.5MHz.
Emergency position-indicating
radiobeacon (EPIRB)
An EPIRB (Fig.17) is used by boats
or ships to communicate a request for
immediate assistance, for example, if
the vessel is sinking or there is a medical emergency.
The device sends a 406MHz distress signal to a Cospas-Sarsat satellite
(www.cospas-sarsat.int/en/), which
then reports the position indicated
by the EPIRB device (obtained via
GPS or other satellite navigation system). It then reports the emergency to
appropriate search and rescue (SAR)
authorities for that area.
If a position was not transmitted, it
calculates the approximate position by analysing the signal.
When SAR are close
to the reported position, they can home
Fig.16: opening a Kia car with
a digital key via UWB. Source:
www.kia.com/mu/owners/
owner-resources/quick-tips/
connectivity/setting-kia-digitalkey2-touch-smartphone.html
in using radio direction finding with
the EPIRB’s 121.5MHz homing signal, strobe lights on the device or the
AIS (automatic identification signal)
on newer devices. An EPIRB is activated either by contact with water or
by manual activation; many are activated automatically and ‘float free’ if
a vessel sinks.
If using one of these devices, note
that it is a free service but it is essential
to register it correctly. They are mandatory in certain jurisdictions for certain types of vessels, but in any case,
they are recommended for whatever
vessel you use.
Note that 121.5MHz is no longer
monitored by satellites (as with older
EPIRBs), but it is still used for homing
purposes and is also the International
Air Distress frequency.
Google Find My Device
This relatively new network will
Fig.17: a typical EPIRB; this
one is a GME MT600G.
Source: www.gme.net.au/au/
emergency-safety/mt600g
Fig.18: an example of items
tracked using Google’s
Find My Device network
and an Android phone.
Source: https://blog.google/
products/android/androidfind-my-device
siliconchip.com.au
Australia's electronics magazine
work with all Android devices (about
three billion of them) – see Fig.18. It is
intended to be equivalent to Apple’s
“Find My” network.
Until recently, only Apple users
have enjoyed the ability to utilise a
huge number of devices that form
a mesh network to find an AirTag.
Now that ability has come to Android
devices (running Android version 9
‘Pie’ or later) via an upgraded Google Find My Device network, which
started to be rolled out worldwide on
April 9th this year – see siliconchip.
au/link/abwp
The rollout appears to have reached
Australia in late May/early June.
Like the Apple Find My network, the
Google/Android Find My Device network utilises a vast network of Android
devices as part of a crowd-sourced
mesh network to communicate the
encrypted location of a tracked device
without needing the knowledge or permission of the other Android users. As
with Apple, the connection is made to
the mesh network via Bluetooth.
Google says that all communications
via the Find My Device network are
end-to-end encrypted, and the location of devices participating in communicating data via the mesh network
is not known to Google or anyone else.
There are said to be numerous privacy
safeguards.
Security alerts will be provided to
users if any unwanted Find My (iOS)
or Find My Device (Android) compatible tags are tracking them.
Like late-model Apple iPhones,
Google Pixel 8 and 8 Pro phones can
be tracked even if they are ‘off’ due to
the ultra-wideband chip being constantly powered.
August 2024 19
Is it possible to defeat GPS trackers?
Sadly, criminals can detect and defeat GPS trackers attached to protected
equipment. Methods used include GPS jammers, scanning for RF
emissions, visual inspection, blocking devices (such as wrapping them in
aluminium foil), physical removal or destruction of trackers and the use of
a GPS signal spoofer to make the device appear to be in a different location
than it really is.
The HHD S7 tracker (siliconchip.au/link/abx0) is an example of an assettracking device that is said to be detection and jammer resistant. The device
is sold as a subscription rather than a one-time purchase.
Third-party trackers designed for
the Find My Device network include
Chipolo and Pebblebee, with devices
yet to be released from Eufy, Jio and
Motorola.
Find My Device seems not to work
on a locked-down privacy phone, as
enabling it would defeat many of the
privacy functions of such a phone.
However, some options and apps are
discussed for the privacy-focused
GrapheneOS at siliconchip.au/link/
abwq
Mobile personal alarms
Elderly people typically use these
devices, which generally are in the
form of a pendant or wristband with
a ‘panic button’. One model we are
familiar with is the LiveLife Mobile
Alarm (https://livelifealarms.com.au)
shown in Fig.19.
When the button is pressed, it calls
a series of nominated contacts, sends
the user’s location via text message and
establishes hands-free two-way voice
communications.
It will also detect calls and issue
an alert. The location is established
via GPS, WiFi and Google Maps, with
communications via the Telstra 4GX
mobile network.
4GX is a Telstra marketing term for
the 4G 700MHz (Band 28) network,
which works at longer ranges than
other parts of the 4G spectrum.
Periodic testing of such life-saving
devices is highly recommended.
Another similar product we saw was
the Adult Buddy Watch (siliconchip.
au/link/abwr) – see Fig.20.
Mobile phone tracking apps
You can install these apps on your
phone and those of willing friends and
family members, including children,
to enable you to see where they are.
Such apps include:
• Familo (available on Android and
iOS) – www.familo.net/en/
• Family Locator (Android and
iOS) – https://family-locator.com
• Find My (iOS) – www.apple.com/
au/icloud/find-my
• iSharing (Android and iOS) –
https://isharingsoft.com
• Life360 (Android and iOS) –
www.life360.com/au/
Pebblebee
These Bluetooth trackers will soon
be offered in versions for both iOS and
Android. The Android version supports Google’s Find My Device network. They do not use UWB.
Pet RFID implants
These RFID devices are about the
size of a large grain of rice and are
used to identify a pet (eg, if they are
lost). Some have considered whether
such a device can be used to track an
animal, but it is very short range only
and can’t be sensed more than about
10cm away.
Pet finders
These use various tracking methods. For short ranges, up to 100m or
so, Bluetooth or WiFi can be used to
track a pet. The location might be
provided as a range with no specific
location or, if the tracker is equipped
with GPS, a location if a GPS signal
is available.
For longer ranges, a tracker con-
Personal locator beacons (PLBs)
PLBs are similar to EPIRBs but are
intended for land-based use, such as
by bushwalkers and outback adventurers – see Fig.21.
They are typically smaller than
EPIRBs and don’t usually have strobe
lights or water activation. If you intend
to use one, make sure it’s registered
correctly.
Fig.19: a LiveLife mobile
personal alarm. Source:
https://livelifealarms.
com.au/product/order4GX-mobile-alarm
Fig.20: the “Adult
Buddy Watch”
from Buddy Gard.
Source: https://
mybuddygard.com.au/
pages/adult-buddy
20
Silicon Chip
nected to a mobile phone network can
transmit GPS coordinates provided
there is network coverage. Devices
that connect to the mobile phone network typically require a subscription
to function.
When phone network coverage is
unavailable, there is also the Aorkuler dog GPS tracker (https://aorkuler.
com). It has its own radio transmitter and receiver rather than using a
mobile phone, transmitting a GPS location to the receiver up to 5.6km away,
depending on terrain, according to the
manufacturer.
We could not find out what frequency or certification it uses, so we
are uncertain if this device would be
legal to use in Australia or New Zealand.
Some trackers enable ‘geofenced’
boundaries to be established, so an
alert is issued if a pet wanders outside
those boundaries. Pet trackers, like
others, require regular battery replacement or recharging, as they can use
a reasonable amount of power. They
typically need to be charged every
few days.
Australia's electronics magazine
Fig.21: a
miniature PLB
(emergency
beacon) suitable
for bushwalkers.
This is the
RescueME PLB1;
it weighs 65g.
Source: www.
rescueswag.com.
au/products/
rescueme-plb1
siliconchip.com.au
Q-TRACK
Q-TRACK produced a range of
devices using near-field electromagnetic ranging (NFER). The company
has since been acquired by GaN Corporation, and the products appear to
no longer be available. NFER is an
emerging technology.
Radio-based key finders
These are always listening for a signal from a dedicated transmitter and
will sound if the transmitter is activated. One example is the “REDPINGUO Wireless RF Item Locator”. The
range is said to be about 30-40m and
it operates at 433.92MHz.
Fleet vehicle trackers
Rental cars, other rented assets and
vehicle fleets are often tracked by
GNSS-based devices to ensure they are
used according to usage agreements, to
prevent theft and for general management purposes. Highly-valued private
cars may use these devices.
Netstar (www.netstaraustralia.com.
au) is an example of an Australian
company that advertises its products
and services for such devices.
Radio Frequency ID (RFID)
RFID tags are attached to objects to
identify them or track their location,
such as the progress of an item down
an assembly line or through a delivery
network like a postal service. RFID tags
may be passive or active. Short-range
passive tags contain circuitry that is
activated by energy from an interrogating radio beam, while active tags
contain a battery and work at much
longer ranges.
Cited ranges for readability of the
tags vary considerably according to
the model and technology used. Still,
typical figures quote up to 1m for a
passive tag at 13.56MHz, up to 100m
or more for an active tag operating
at 433MHz or 2.45GHz and 200m or
Fig.24: the Lars Thrane LT-3100S GMDSS (Global Maritime Distress and
Safety System) for SSAS and other forms of ship-to-shore voice and data
communications via the Iridium satellite system. Source: www.prnewswire.
com/news-releases/new-era-for-safety-at-sea-as-first-ever-iridium-gmdssterminal-is-unveiled-300861105.html
higher in other frequency bands.
Common examples of RFID devices
are pet ID implants, inventory tags in
stores, access control devices, trackers
for railway rolling stock, trackers for
shipping containers, some passports
(including Australia’s), books in some
libraries, toll collection devices and
many others. The devices are generally very cheap.
We published a DIY RFID tag design
in the July 2023 issue (siliconchip.au/
Article/15860).
Samsung SmartTag2
The SmartTag2 (Fig.22) uses Bluetooth and UWB for tracking and has a
range of up to 120m from the nearest
phone. It does not support Google’s
Find My Device network and only
works with Samsung Galaxy devices.
Nevertheless, it has received favourable reviews, such as siliconchip.au/
link/abws
It has a claimed battery life of 500
days, or 700 days in power-saving
mode.
Shipping container tracking
Shipping containers are tracked
using various technologies and sensors, such as GPS with connectivity
provided by Bluetooth, LPWAN (Low
Power Wide Area Network), mobile
IoT and satellite. Some also include
door and movement sensors, temperature sensors and weight sensors.
One example is the Vimel VIM4GCONT (Fig.23). It has a five-year battery life with daily location updates,
stores location data if out of network
coverage and more (see siliconchip.
au/link/abx3).
Ship security alert system (SSAS)
The SSAS alerts authorities that a
ship is under attack by pirates or terrorists – see Fig.24. An SSAS report
contains the ship name, unique identification numbers like MMSI (Maritime Mobile Service Identity), IMO
(International Maritime Organisation) number and call sign, the date
and time, the ship’s current position,
speed and course.
Fig.23: the Vimel VIM-4GCONT is a
shipping container tracker.
Source: Security Lab –
siliconchip.au/link/
abx3
Fig.22: typical use cases for a Samsung SmartTag2. Source: www.samsung.
com/au/mobile-accessories/galaxy-smarttag2-black-ei-t5600bbegau
siliconchip.com.au
Australia's electronics magazine
August 2024 21
Figs.25 & 26: the mOOvement GPS ear tag (www.moovement.com.au) for domestic cattle (left). This model has a long
battery life due to onboard solar cells for charging. As one use example, data from the device can be used to create a heat
map of grazing patterns (right).
Sound-based devices
Examples of these devices are early
key finders that require you to whistle
or clap your hands to activate a tone.
You could then ‘home in’ on the tone
using your ears. However, they were
generally unreliable and are now
largely obsolete.
Tile
Tile trackers (www.tile.com/en-au)
are Bluetooth-based tracking devices
for keys, wallets, luggage and other
objects. If a tagged item is lost, a smartphone app can make the Tile device
make a noise, and the last known
location will be shown on a map. A
lost phone can also be made to make
a sound by double-clicking on a Tile
tracker.
orbit at 850km altitude, orbiting about
every 100 minutes. A message length
of 3-31 bytes is allowed per satellite
pass. From there, data is transmitted
to a ground station.
Wildlife is also tracked using mobile
telephone networks. When the animal
is out of range, tracking data can be
cached. VHF, UHF or LoRa can be used
for shorter-range communications.
There is a free worldwide animal
tracking database where researchers,
journalists, students or developers
can access animal tracking data. It
is called Movebank (siliconchip.au/
link/abwt).
There is a free app for members of
the public to track various animals;
see siliconchip.au/link/abwu and the
YouTube video titled “Animal Tracker
App” which you can view at: https://
SC
youtu.be/wdG99OdwpWE
Animal tracking
Depending on the species, wildlife
and farm animals can be tracked with
GPS tags or collars.
For domestic livestock such as cows,
a GPS ear tag can be attached (see
Figs.25 & 26). In that example, GPS
location data from the tag is relayed
via a low-cost LoRaWAN (Long Range
Wide Area Network) network on the
farmer’s property, with a range of about
8km. For more information on LoRa,
see page 21 of our Digital Radio Modes
article from May 2021 (siliconchip.au/
Article/14848).
In the case of wildlife that travels
a long distance, tracking can be performed via the Argos satellite system (www.argos-system.org) with its
uplink at 401.65MHz (see Fig.27). This
system has seven satellites in polar
22
Silicon Chip
Fig.27: a wild animal (a female elk) with a North Star GPS tracking collar.
Source: www.northstarst.com/tracking-wildlife/wild-animals
Advice for tracking pets
If you use a tracker for your pet, you should familiarise yourself with its
operation, capabilities and limitations before it is needed. That includes
replacing or charging the battery when necessary.
I know of someone who did not do this, and when their pet wandered off,
the device (which they had never tested) did not work! Fortunately, the pet
was found the old-fashioned way, with a person who found it calling the
phone number on the collar.
Australia's electronics magazine
siliconchip.com.au
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