The distance is determined by knowing the delay time of the echo signal and the propagation speed c0. The distance thus determined represents the distance in a straight line between the radar and the target and is called the "inclined distance". The actual distance is the distance in the horizontal plane (at ground level) between the radar position and the projection of the target position in this plane. The target height must be known to determine this distance. Because the signal travels between the radar and the target twice (round trip), the delay time is divided by 2 to obtain the propagation time from the radar to the target. The following is the formula for calculating the inclined distance:
where: t=delay time, R=inclined distance
By measuring the delay time of the signal t, the distance R is very easily calculated using the formula. The delay time is the time required for the probe pulse to travel the distance to the target and back (the time elapsed between the transmission of the pulse in space and the detection of its reflection by the receiver).