I certainly wouldn't want to trust my life to the integrity of a -130 dBm strength signal. Particularly if I'm traveling in a tunnel, or heck, deep forest.
I think, though, that if the alternative is to trust my instincts (which I don't have), then I'd rather trust that -130 dBm strength signal. I think that my instincts are the secondary factor when I get lost in the forest, not the first factor. If I have no reason to think the GPS system is deceiving me, I would trust it.