A specific requirement to produce individual trajectory data for each of a cluster of parachutists dropped from an aircraft has been studied. When the trajectory or velocity is required of a number of similar objects released simultaneously, or in rapid succession, and which thereafter travel at different rates, difficulty is experienced during analysis in positively identifying each object throughout its flight path due to its similarity to its neighbours, particularly when working from records taken by a kinetheodolite at intervals of 1 second or 0.2 second.nTo resolve this difficulty stereophotography with wide angle lenses has been used to differentiate the objects prior to measurement of their positions from the photographic images.nRecording 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 metres were experienced the rms of the residual error after trends had been removed was 0.5 metre.
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