... observatory code . ... projections of the geocentric radius-vector of observatory on the Earth equatorial plane and on the Earth rotation axis, dxy and dz, correspondingly; both quantities are expressed in parts of the equatorial radius of the Earth taken as 6378.137 km; they are known as parallax constants . ... The observatory code is a string that contains three symbols, the first one being digit or letter, the second and the third ones being digits. ... So, code B47 means number 1147. ...