Telemetry Beacon
Capabilities
The telemetry beacon sends its GPS location using the Iridium network. Every message sent by Scout includes GPS latitude and longitude (2.5m horizontal accuracy) and battery level. Location messages can be sent at 3, 10, or 60 minute intervals, and the unit can be put to sleep for up to 24 hours. All intervals can be set through the app.
The Iridium network is a satellite-based global communications system that provides 100% planetary coverage, including the poles. It operates through a constellation of 66 satellites in Low-Earth Orbit that relay data to ground stations and user devices. Iridium has data services in remote locations.
Turning the beacon on
To start the telemetry beacon remove the plastic collar from the antenna mast.
The beacon is powered on and off with a magnetic switch in the mast. When a magnet is near the switch the system powers off. The magnet embedded in the collar needs to be aligned with the marks, otherwise the unit could turn on.
When the unit is first turned on a red light near the base of the antenna will be flashing. The light is very faint in the daylight, but easy to see in the dark.
Checking for messages
Once the beacon is on, it will try to send a message immediately, there should be a message in the app within 5 minutes. It can take as long as 20 minutes if conditions are poor. This can happen if Scout can’t connect to the Iridium satellite network. Try to put the Scout beacon in as open an area as possible, with the antenna facing upward. Being next to buildings or walls can negatively impact the signal strength.
Message Schedule
After power on the beacon tries to send a message immediately (usually arrives in app within 5 minutes) and after the first successful message it defaults to a reporting interval of 10 minutes.
The 10 minute interval is pegged to actual time, beacon will try to send at :00, :10, :20, :30, :40, :50. There are no retries in this interval. Failed messages will be simply missing from that sequence.
The 1 hour interval: The beacon will try to send at :00, :10, :20, :30, etc . The sequence will end when a message is successfully sent.
The 3 minute "last mile" interval: The beacon will try to send at :03, :06, :09, the sequence might become somewhat unpredictable as there could be overlap between sending attempts and the next scheduled message. The beacon should get the message out in under 5 minutes.
Effective Transmission Rate of Messages
The effective transmission rate (Tx) is the actual interval of successfully sent messages. This can be much longer than the reporting interval since the beacon is not using a saltwater switch or any other sensor to determine it is at the surface. Rather the beacon attempts to send messages at some regular interval set by the user. This coupled with the diving behavior of the whales makes how often Scout sends a successful message somewhat random.
As such the effective transmission rate is driven by 4 factors: (1) the reporting interval set by the user (2) the average dive time of the whale (3) the average surface time of the whale (4) the likelihood of the Iridium network to be available. Using these variables we have simulated the effective transmission rate for each interval. Big thanks to Doug Sandilands for providing the data science and code to do this!
The results below use the following parameters (assumptions) in the simulation:
simulation duration: 8 hours
min surface duration: 2 minutes
max surface duration: 5 minutes
min dive duration: 2 minutes
maximum dive duration: 10 minutes
GPS timeout: 4 minutes
Likelihood of send success above surface (e.g. Iridium availability): 80%
The effective transmission rate for each interval is the average of 10 simulations
3 minutes
6 minutes
10 minutes
19 minutes
60 minutes
114 minutes
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