Note the deep valleys, really more indentations in the land. You just can't see much sky, plus I've always found Pine Trees are pretty bad in terms of RF attenuation. I'd have 3D lock, then 2d lock, then I'd loose all but 2 satellites, then I'd get a lock again. It wasn't a big deal, we didn't need the GPS at all, there were so many people to just walk the area and we used cell phones and HT's to coordinate.