Determining the trajectories of multiple objects using stereophotography and photogrammetry

A specific requirement to produce individual trajectory data for each of a cluster of parachutists dropped from an aircraft was studied. Stereophotography with wide angle lenses was used to differentiate the objects prior to measurement of their positions from the photographic images. Recording the instant of taking each stereophotographic pair against time enabled trajectories and velocities to be obtained, a cross check being obtained from kinetheodolite recordings of the positions of some of the objects. Although absolute positional errors of up to 41 meters were experienced the rms of the residual error after trends were removed was 0.5 meter. The photogrammetric equations used are discussed in the annex.