The Radar Method

Let $n_1$ be the integer that labels a pulse emitted by radar unit B. If that pulse gets reflected, or partially reflected, by a scattering event, then let $n_2$ be the integer which the clock assigns to the reflected pulse as it enters the radar receiver. These two integers,

$$(n_1,n_2)~,$$ (10)

generated by this radar ranging process are the radar coordinates of the scattering event. They assign a unique spacetime location to the scattering event, namely $(t,z)$ as determined by

$$\begin{array}{cc} T_1-Z_1=t-z&\textrm{(pulse moving to the ... ...\ T_2+Z_2=t+z&\textrm{(pulse moving to the left)} \end{array}$$ (11)

Here $(T_1,Z_1)$ and $(T_2,Z_2)$ are those two events at radar unit B which mark the emission and the reception of a pulse at B.