I just got back from my trip down to Utah and managed to spend some time in tight canyons. I can use my map/compass pretty well but GPS is my primary nav tool. Just like every canyoneering book said no GPS signal in canyons for miles. That got me wonder... how would a PLB fare in such an environment? I'm all for walking a few steps (tired/injured) to get my signal but when I downloaded my waypoints I had 1.5 mile gaps.