Figure 2.

The linear geometry that results from assuming that the particles' velocities remain constant. A particle following a linear trajectory connecting the 3‐D positions ${\overline{r}}_{1,2,3}$ appears within the image at the locations l _1,2,3 when observed at the times t _1,2,3. The x and y components of each 3‐D position with respect to the radiant point are also shown where the x direction is parallel to the line connecting the observations within the image plane, and the y direction is parallel to the camera boresight. The z direction completes the right‐hand rule, such that the z component of each position is zero.