Wave propagation takes place between the transmitter located on the ground and the receiving equipment also located on or near the ground, such as antenna systems, aerials, mobile radios, car radios or cell phones, within the atmosphere. These waves may be ground waves, as in the case of long waves, space waves reflected by the ionosphere, as in the case of short waves, or radio waves transmitted via a line-of-sight link between transmitter and receiver, as in the case of optical and radio directional radio, VHF, television and mobile radio.
Terrestrial propagation applies equally to radio frequencies modulated with analog or with digital signals. For example, digital radio or digital TV can be transmitted terrestrially, via cable networks or by satellite. Examples where terrestrial transmission appears in the designation are Digital Terrestrial Television Broadcast( DTTB), DVB Terrestrial( DVB-T) or Terrestrial DAB( T-DAB).