Fig. 3. A typical transmission mode waveform collected with 0.28-m long rods in sand saturated with 10-dS m^–1 NaCl solution. The fitted tangent lines used to determine the one-way pulse arrival time through the medium and cables (t_n = 20.4 ns) are shown. The rise time, t_r = 7 ns, is the time delay between t_n and the time at which the waveform amplitude is half of its eventual maximum, t_0.5 = 27.4 ns. The one-way travel time through the cables and an air-filled container is t_n-air.