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It is true that canopy will block tracking and OK messages. I'm not sure about HELP. I'll have to check the manual again, but I believe that HELP and 911 messages will be sent whether or not SPOT is able to get a GPS fix - unlike Track and OK.


With the GPS satellite system, you can receive your location data only. So the SPOT must use something else to transmit your position, and send a HELP call. If it uses the cellphone network, which uses microwaves, which are a higher powered signal, you will be ok if there is a cell tower you can reach. If no cell tower, you are SOL.

I'd be curious as to which networks the SPOT uses for which functions. Clearly it must use the received GPS signals to tell the device where you are, but how does it tell a central location where you are?
SPOT operates on the GPS network only for locating the person and through the commercially owned Globalstar Network for transmitting. The signal power is weak and is similar to the amount of power being received (0.6W). This isn't enough power to get the signal through tree canopies, keep it from bouncing off canyon walls, etc. All the things that plague GPSs in receiving a signal also plague the SPOT when receiving and sending.

The SPOT unit must get a GPS lock before it can tell anyone where the person is. It will send a signal through their satellite system that the person is in trouble, but no one will know where that person is. At least it will get the ball rolling...

The bottom line is that it is unreliable in emergency situations except when the conditions are near perfect for sending and receiving a GPS signal. We all know how reliable that is. <img src="/forums/images/graemlins/confused.gif" alt="" />
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