The PID is a 6-character code that the NGS uses to keep track of control points in their NSRS computer database. This code was invented when the NGS computerized its records. Prior that computerization effort, each control point had a "designation", or name that adequately identified it within its local area, but which may have been duplicated in other parts of the country. The designation is a name chosen by the surveyor who establishes the point. The "PID" is chosen by the NGS.