Forum AVCOM aus Südafrika
Another difference is that ELT's are silent until - in case of an accident - they (supposedly) come on. In reality that only happens (for a variety of reasons) only in 1 out of 3 cases. Globalstar (Spot) or Iridium-based sat trackers (like Delorme, Garmin inReach or Spidertracks for example) on the other hand transmit position updates all the time. Your flight follower needs to start worrying only once the signal is lost, or the GPS ground speed shows zero, but would invariably see your most recent location before the incident.
With sat trackers, you have a number of third-party value-added service providers (VAS) who offer server-based flight-following and exception monitoring. I use ProteGear's data plans (https://www.protegear.de/english/protegear-smartsafety/) to connect my Garmin inReach to the Iridium network (instead of Garmin's own, less flexible data plans). ProteGear also does monitoring of my flights:
- Start monitoring when I move beyond a set radius
- Suspend monitoring when I send "Pause" message
- Send alert SMS or emails to designated alert responders if the sat signal is lost or I stop moving
If everything is set-up correctly, I practically do not need anymore somebody to watch the sat trace on the web. ProteGear will conveniently notify my family when I have crashed.
A secondary benefit of Iridium-based sat trackers like Delorme/Garmin inReach or Spidertracks is that they offer 2-way messaging. The Spidertracks device only does this as long as the tracker is connected to ship power (it doesn't have its own battery); their messaging is more geared towards operational communication.
The Garmin inReach is more like a personal survival tool. It runs of its own battery, and should allow to communicate even if the ship, or ship power, is lost (provided the inReach device is carried on the body and not left behind in the burning wreck). It must be immensely comforting not only being able to call for help, but to actually know that help is on its way, and to tell responders what is wrong.