They are at known locations on the ground, so the paths between them are also known, which is very important from a reliability perspective from the whole network.
它们位于地面上众所周知的地点， 所以它们相互之间的道路也是清晰的， 这对于整个网络的可靠性来讲非常重要。 这对于整个网络的可靠性来讲非常重要。