The velocity factor in the reflection method stands for the ratio of the propagation speed of electromagnetic waves in a cable to the speed of light. The speed of propagation of electromagnetic waves in a cable is usually given in relation to the speed of light. The speed of light is approximately 299,792 kilometers per second. The velocity factor is used to calculate the actual propagation speed of the signals in the cable. If a velocity factor of 1 or 100 percent is specified, it means that the electromagnetic waves propagate at the speed of light in the cable.
For example, if a velocity factor of 0.80 is specified or determined, it means that the electromagnetic waves propagate in the cable at a speed of 0.80 * 299,792 kilometers per second, or 239,834 kilometers per second. The velocity factor is important for making accurate length measurements using the reflection method. By taking into account the actual propagation speed of the signals, the measurement accuracy can be improved. The velocity factor varies depending on the cable type and can be specified by the manufacturer or determined experimentally.