How to Track your Teams?
This document will try to explain the different options on the GPS Tracking of Teams in the field.
Many different systems are now available, but all of them have their pro’s and con’s.
APRS VHF Radio based trackers
Commercial VHF radios with build-in GPS data system
GPS Microphones
Satellite Trackers
Smartphone Trackers
They tell you where (they think) they are
APRS VHF Radio based trackers.
APRS
stands for Automatic Packet Reporting System, based on the AX-25
communication protocol. It is a system designed to be used on
low-bandwidth standard VHF FM radio’s.
The SARTrack system was originally built
around this protocol, because it not only enables GPS Tracking, but
also the transmitting of Messages, manually added Objects and many
other kinds of data, all over the same system.
Over the last 20
years, a world-wide APRS Internet Server system has been established,
which connects all local Amateur Radio (HAM) APRS Radio repeaters
together, so it is now possible to view stations from all over the
world on a APRS program connected to one of these APRS Servers.
Cheap
of-the-shelf APRS Tracker boards are available, which together with an
GPS unit and any radio can be built into a complete APRS VHF Radio
tracker.
Light-weight portable Digital Repeaters
(Digipeaters) will enable the tracking in mountainous terrain, as all
Digipeaters will automatically link together to transfer the data on
towards a SAR Base.
Initially SARTrack Limited produced complete APRS
Trackers and Digipeaters, using a New Zealand “Type Approved” radio,
which can legally be used on a commercial VHF frequency by SAR Teams.
In New Zealand, SARTrack Limited owns a nationwide VHF frequency allocated for this.
However, SARTrack Limited no longer builds these trackers.
There
are complete Amateur Radio VHF radios with build-in APRS available from Yaesu
and Kenwood, but these can only be used on the Amateur Radio
bands, by licenced operators. Also, these radios are highly complicated
in their use, and not suitable for non-technical people in the field.
A
Radio Modem with a handheld radio (connected to an external antenna)
will be used at a SARTrack laptop at the Base to receive the tracking
(and other APRS) data.
Pro’s:
-
APRS Trackers use local VHF radio, and Digital repeaters to get the
position reports back to the SAR Base at the remote location. It works
independent of any outside communication like Internet, Iridium
satellites or mobile phone networks. Due to the design and the
use of portable Digipeaters, location data from trackers in deep
valleys can be bounced back to the Base by ‘daisy-chaining’ 2 or 3
Digipeaters. It is independent of the Voice radios and the voice
repeaters, and in practice it is often seen that while Voice
communication with some teams is nearly impossible, the APRS Tracking
data is still perfectly clear, so the position of the (moving) Team is
still updating on the map. Also, a 'Priority/Emergency' alarm can be activated by the teams in the field.
- Within limits, it is
possible to use the APRS Radio system to connect multiple laptop
computers together by radio in an disaster area for emergency
communications when no other digital communications are available.
However, due to the limited bandwidth on the VHF radio channel, only
very small Messages, Operation Logs and other data can be transmitted
and packet loss is to be expected.
- Due to the
(linked) Digipeater system, the coverage will often be better than the Voice
system, resulting in additional safety for the Teams as their location
will still be clear, even if voice contact has been lost. They
will also be able to activate a APRS Priority/Emergency alarm.
-
The system is independent from external communication nets like
Internet, Iridium satellites or cellular networks.
Con’s:
-
There are no complete APRS Radio trackers for commercial use on
the market. If you want to legally have non-HAM SAR Teams using APRS
trackers, they must be locally build, using a Type Approved
radio. This includes the Digipeaters.
- Every Team needs one APRS Tracker in addition to their VHF Voice radio.
-
Portable Digipeaters must be deployed at the same time as any
portable Voice repeaters, but possibly not at the same location.
Commercial VHF radios with build-in GPS data system.
SARTrack currently supports the following commercial radios:
- Kenwood FleetSync, Icom, Tait, Motorola, Hytera.
The
following general information is based on these radios.
The radios
combine VHF Voice and GPS Location data on the same FM radio channel.
The radios can transmit their GPS location to the Base, by
regular (Time) transmission, on PTT release and on a 'Poll' request from the Base (e.g. by interrogating
the remote radio from the Base computer) .
As they work on a
standard VHF FM channel, they work over all existing Fixed and Portable
voice repeaters in the area. Generally the
Data transmissions sound will be suppressed on radios of the same brand, so the data bursts will not be heard.
However, any other radios on the same channel will hear the data
transmissions.
Note: An external “Backpack” antenna will greatly improve radio
coverage of handheld radios and is strongly recommended!
One (Base) radio (connected to an external antenna) will be
connected to a SARTrack laptop to communicate to the radios in the
field.
SARTrack will convert the location data to APRS
format, and transfer this to all other connected SARTrack computers.
Pro’s:
-
Only one radio is used per Team for both Voice and GPS location.
- The existing fixed and portable Voice repeaters can be used.
Con’s:
-
The quality of the Data transmissions is highly dependent on the
Voice Repeaters used and especially when multiple voice repeaters are
linked, data loss may occur.
Data loss will be much higher than
when an APRS system (with Digital Repeaters) would be used.
GPS Microphones.
Third-party GPS Microphones can be purchased which can connect to a variety of VHF radios.
They
will generally transmit a burst of GPS location data after the user has
finished a Voice transmission and Time based. As they are not really part of the
radio, the quality of the GPS data being transmitted over the VHF radio
may not be as good compared to a radio which has a build-in data
protocol.
One GPS Microphone with a handheld radio
(connected to an external antenna) will be used at a SARTrack laptop at
the Operations Base to receive the tracking data.
SARTrack will convert the location data to APRS format, and transfer this to all other connected SARTrack computers.
SARTrack currently supports 2 GPS Microphones.
Pro’s:
- Only one radio is used per Team for both Voice and GPS location.
- The existing fixed and portable Voice repeaters can be used.
-
The system is independent from external communication nets like
Internet, Iridium satellites or cellular networks.
Con’s:
-
The range of the Data transmission will likely be a bit less than a
radio with build-in data protocol, and the range will be a lot less compared to APRS based trackers.
-
The range of the Data transmissions is highly dependent on the
Voice Repeaters used. Especially, when multiple voice repeaters are
linked, data loss may occur.
- The Data transmission bursts will be heard over the voice channel, which many users will find annoying. (* But consider the alternative)
-
Because the user is using a separate microphone, they will have the
actual radio clipped to a belt or harness. This means a major reduction
in radio coverage compared to holding the radio in front of their
mouth. An external antenna may be required to improve coverage.
Else they will have to hold the radio in to the air, while taling
in the microphone.
Note: An external “Backpack” antenna will always greatly improve coverage of handheld radios.
SARTrack strongly recommends the use of a backpack antenna.
(*) The alternative of not
having the 600 miliseconds 'burp' on the voice channel, will be a
minute of forward-and-backwards chat between the Teams and RadioOps,
verbally passing on their location, including readbacks and errors,
every half hour. What would the users on the channel rather have?
Satellite Trackers.
There
are now many Satellite Trackers available. Most of these are
based on the Iridium satellite network, which is a constellation of 66
LEO (Low Earth Orbit) satellites, moving around the earth at 780 km
altitude at a speed of 27,000 km/h.
Trackers which are based on a
Geo-stationary satellite like the Globalsat system are unsuitable for
SAR use, because they use a single satellite at a fixed position in the
sky at 40,000+ km altitude, and they will only work reliable in
non-mountainous areas with no tree cover.
The main
problem of satellite trackers is that the Tracker must have a clear
view of the sky (at least most of the time) to be able to transmit its
GPS data to the orbiting satellites. However, modern satellite trackers seem to do a good job in difficult conditions.
Once the data is received by
a satellite, it is transferred via the other satellites to an Iridium
ground station, probably in the USA. From there it will be
transferred over the worldwide Internet network to the (Web) Server of
the tracker provider. Then the SARTrack computer will connect via
the Internet to the Web server to retrieve the tracking data.
The
long Internet links involved mean that while your Teams are in the
field only kilometres away, you are totally dependent on the Internet
connections in the world, and especially the Internet connection
required by your remote Operations Base.
If that base
is in cellular network coverage, you may have Internet access via the
Broadband network.
Else, the best option would be a two-way
satellite Internet system, which itself is based on a geo-stationary
satellite, at a fixed point in the sky which must be in clear view from
the location of your remote base.
If any of these links fail, you will lose the tracking of your teams in the field.
One more option is possible using the SARTrack system and APRS Digipeaters:
One
(permanent) SARTrack PC is based at a home location with an APRS TNC
and radio connected. With its permanent (ADSL) Internet connection if
will receive the satellite tracker feed(s). SARTrack will convert these
into APRS data, and transmit this over the TNC radio modem to nearby
APRS Digipeaters. A SARTrack computer at the remote Operation's area
will use a TNC Modem to receive the data from the Digipeater network.
This setup not only makes it possible to receive satellite trackers
data at a remote location without Internet access, but also enables
Message communication between the remote Operations Base and any
SARTrack computers on the Internet. Legally, both SARTrack computers
will have to have a Amateur Radio callsign/operator attached if you use
the amateur radio APRS frequency (New Zealand users can use the
SARTrack private APRS VHF frequency).
NOTE:
Having a reliable two-way portable Satellite Internet system available, will
make you independent of Internet communication failures during a local
emergency where all local communications have failed, as in storm,
flood or earthquake disasters.
Pro’s:
- Does not require any local radio repeaters to set up.
Con’s:
-
Reliable Internet access is required at the remote SAR Base
(except in the example above, using APRS repeaters)
-
In steep mountainous terrain and under heavy tree cover, the
Trackers may not be able to connect to the Iridium satellites.
- There is a significant ongoing (monthly) cost involved, even if they are not in use.
Smartphone Trackers.
With
most Smartphones it is now possible to transmit APRS tracking data,
when these phones have network coverage and Internet access. This
system can be very useful in cases where good mobile phone coverage is
available, and the Base also has Internet access, for example in urban
searches (for Alzheimer etc.).
One problem with these Tracker
programs is that it uses a lot of battery power, and may flatten the
cell phone battery in just a few hours. External power (via a car
adaptor) will solve this issue.
The Tracker will connect to an APRS
Server on the Internet, which will distribute the data to all connected
SARTrack computers and other Smartphone Trackers.
Pro’s:
- Very simple to set up, will work well in urban areas.
-
The Smartphone Trackers will also be able to see the location of
any other Trackers, and receive/transmit Messages over the APRS
network. And obviously, they have standard messaging and can be
called!
Con’s:
- Good cell phone and mobile Internet access required for the Trackers, and Internet for the Base.
- Not suitable in remote areas.
A good Android Tracker is APRSDroid, which you can purchase in the Google Play shop for only US $6 .
Click here on how to set it up.
The SARTrack Member App (Android).
As
from 2019, SARTrack now has a special Android App, which will link into
the Database Servers, and will enable the tracking of the device
directly into the SARTrack system. In addition it has capabilities to
transmit 'Clue's (complete with a photo) directly to the Operation
management, it has a Message system, access to the Operation Log (if
allowed) and much more.
They tell you where (they think) they are...
The Teams in the field are trying to determine where
they actually are, and then try to communicate this by Voice radio to
the Operations Base.
Last century, they did this by locating some
features around them, and trying to locate themselves on their map.
They would then transmit their location based on a huge Grid
reference, which made the required digits to be transmitted also much
smaller.
This century, they have a GPS with them. Now they read their own location from the GPS, and transmit their Grid
location, but often still in a huge Grid reference, to keep the
transmitted digits as short as possible... But by doing so, they often read
the wrong digits from the GPS.
Pro's:
- You heard their voice, so they are still okay.
Con's:
- They will occasionally transmit the wrong grid coordinates.
- The Grid coordinates used may be so rough as to be useless in this day and age.
- The Radio Operator may have heard wrong.
-
The Radio Operator must pass on the information to the Operations Team
on paper, or by manually entering it on the computer, again with
possibility of errors.
- A huge amount of (radio) time is wasted by the continuous position reports of all the Teams.
There
is no reason why you can't mix various Tracker systems at the same
time. You may have a couple of satellite trackers in conjuction
with VHF radio based trackers, depending on the requirements of the
teams, some of which could be in vehicles or aircraft. SARTrack wil
combine them all and distribute them accross all SARTrack computers.
I
hope this document has giving you some information on which you can
base the most suitable tracking system for your organisation.
Updated September 2019,
Bart Kindt
SARTrack Limited
http://www.sartrack.nz/
Attachements:
Set up APRSDroid.
On first use, on the Startup screen, enter the Callsign you are going to use (without
SSID eg -1 , -9 etc), and the Passcode for this Callsign. When
you are an Amateur Radio operator, this would be your callsign. Other
users should use the callsign they are also using for their SARTrack
computers and the same Passcode, but in the next steps you MUST add the special SSID to your Callsign for this device.
In Preferences, enter the following entries:
SSID: Select a SSID here, which is different than any others you may have in use for your SARTrack computers.
APRS symbol: The default is /$, which is a Telephone. A 'Person' would be /[. A full list is here (PDF).
Comment field:
Enter your Tactical callsign here as follows: [:My Tactical , or: My
Information[:My Tactical. Everything behind the [: is considered
the Tactical callsign.
Location Source:
The default is "SmartBeaconing Position". This will transmit your
position when you move allong, or turn corners. I rather use
Periodic GPS/Network Position, every 10 minutes (you can set that later)
Location Settings:
- Minimum Update Time: If you use "Periodic GPS/Network Position" above, set here the time between transmissions.
- Minimum update distance: This will transmit your location when you move more than x kilometers.
- GPS Precision: The default is "Medium". I suggest you use "Medium" or "Low", as the GPS chip will quickly drain your phone's battery! Keep a close eye on the battery level, if it drops to fast, try to use "Low".
Position privacy: Leave as default.
Connection Protocol: Leave as TCP
Connection Preferences:
- Server:
For the world-wide APRS-IS network (only with valid Amateur Radio
callsign!!) use "rotate.aprs2.net", for SARTrack private SAR servers
use "sartrack.nl" or "sartrack.co.nz" (New Zealand users only)
- Neighbour Radius: Set to the distance from your position you want to receive data from.
- Packet filter:
I suggest you use something like this: "u/ZL4FOX* p/ZL". The first bit
with ZL4FOX allows you to communicate with me (the SARTrack developer).
This is Optional. The second bit after p/ means that you will receive all data
from stations starting with
ZL. You can add more like this: p/ZL/VE/PA etc. Just make sure
you add any stations you need here. NOTE: The Radius filter which you
entered earlier will get you any stations within that area, as long as
they transmit their position. Any stations which send a beacon without
a position will not show up, unless you put them in above filter(s).
Be careful, above
example would get you a full feed of ALL Canadian, ALL New Zealand and
a lot of Dutch stations. This will cause a huge amount of traffic on
your phone's data connection! So only select what you really need.
Leave all other settings as default.
Exit
the Preference menu, and select "Start Tracking". The phone will
connect to the APRS Server and transmit its position as per setup. You
will see your phone on all SATTrack computers connected to the sare
APRS network. You can exit the App, and it will keep running in
the background. Keep an eye on the battery level!
NOTE1: To
minimize battery (and data) use, when you only want to be Tracked, set
the Neightbour Radius to 0, and leave the Packet Filter empty. This way
you will not receive continuous incoming packets, which would keep the broadband connection open.
NOTE2: If you are operating from a vehicle, keep the SmartPhone connected to a car (cigarette lighter) charger.
Note: If you are using a Apple IPhone, there are APRS clients for these as well, and you can use the same basic setup as above.