868. The Shabbos Boundary When Camping
Shabbos 27:3
Regarding one who travels beyond the Shabbos boundary higher than ten handbreadths (about 30”) from the ground, such as by jumping from pillar to pillar when none of the pillars has a surface of four handbreadths by four handbreadths (about 12”x12”), the matter is unresolved whether the Shabbos boundary rules apply at this height. However, if one walks on a surface that is four handbreadths by four handbreadths, it is the same as walking on the ground and the Shabbos boundary rules apply.
Shabbos 27:4
If a person spends Shabbos in an animal enclosure in the wilderness, a corral, a cave or a similar kind of private domain, he may traverse its entire area plus the size of a square extending 2,000 cubits in every direction. Similarly, one who spends Shabbos in a valley may travel to the limits of a square that extends 2,000 cubits in every direction from his location when Shabbos arrived; this is true even if he was sleeping at the time and did not consciously designate the place as his base for Shabbos. If a person is walking in a valley and doesn’t know how far his Shabbos boundary goes, he may travel 2,000 normal steps.