This is when you put up a very low to the ground HF dipole and operate the mesh in NVIS (near vertical incidence scattering) donut mode. Your node won't be able to contact anything local but it will contact a ring region about 100 miles around you with a many tens of miles gap. It is much harder to find an NVIS transmitter with multi-lateration which is why it is the mode most commonly used in military operations (for ground troops).