It really coincides with the satelite coverage for the phone service. SPOT Inc is a subsidiary of Globalstar, uses the same network of satellites.

Ask around, if your area does not have very good coverage with Globalstar service the SPOT isn't going to work very well.

On the other hand, the SPOT transmits so much less data compared to voice that in areas with iffy satphone coverage the SPOT will work pretty decent.

The other thing to be aware of is how hit and miss the SPOT is in tree cover. Sometimes it will work, sometimes it won't.


So, the short answer; I don't have a definite answer for you on what latitude it doesn't work reliably past, or if there even is one now. My experience with the SPOT is from when it first hit the market.