Southworth and Hawkins (1963) described a criterion for distinguishing stream meteors from sporadics. A function D of the orbital elements was proposed as a measure of the difference between two orbits. A sporadic meteor was then defined as one whose difference D from all other observed meteors exceeded an empirically determined minimum. Any two meteors that differed by less than the minimum were defined to be members of the same stream.

D may be taken to be a distance in a five-dimensional space, whose coordinates are orbital elements. It is now proposed that a stream would be better defined as a statistically significant concentration of meteors in this orbit-space. The procedure has been programmed for a computer, and applied to the Harvard-Smithsonian radar observations.