By classical methods it is possible, at least in theory, to determine the trajectory of an object moving in a central gravitational field by passive observations of angular position. This method of trajectory determination was worked out and programmed for the case of observations made from a rotating earth. A computer program was developed for the calculation of observations of angular position and rate of change of range. Normally distributed errors were added to the computed observations in such a way that stochastically independent trajectory determinations could be made under the same circumstances. This resulted in a simulation of the operation of observing and determining the trajectory. Examples were computed to display the effect of observation errors on impact point determination.