Resurrecting this thread....
On wpsmb, the question was asked:
"Does the SPOT II Tracker/Messenger work ok on the Main Whitney Trail?"
Yes, it does. I've seen the Spot tracks from several Whitney regulars, and it works well most of the time. Just be sure it is carried high on your pack facing the sky. I stick mine on the top of my pack's shoulder strap.
As for its not working sometimes: I've seen Spot tracks where an erroneous location was sent, showing the position maybe a half mile south of the person's obvious location. Those things can happen in canyons like Whitney Portal. Mine reported a bad location along the Vernal Falls trail in Yosemite last time I was there. But the majority of locations are exactly right on the trail.
And once in a while, there will be NO signal getting out. That happened along Bubbs Creek in Kings Canyon. The canyon walls are so high that the unit either could not "see" enough satellites to get a good location, or could not send its signal to an overhead satellite.
The other mistake users make with the unit is to turn it on, send an OK signal, and turn it off as soon as its lights blink that a signal was sent. However, even if a signal was sent, there are time periods when no receiving satellite is overhead, so the "sent" signal is never received. The unit should be left on at least 20 minutes, maybe even longer, to ensure an OK signal gets out.
