Patent GB-683536-A (GB)
Title: Improvements relating to a system and means for the location of moving objects
Inventor: DODDS JOHN MATHIESON
IPC: G01S1/02
Filed: 1949-10-07
Abstract: 683,536. Air traffic supervision; electric indicating systems. METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. May 25. 1950 [Oct. 7, 1949], No. 25860/49. Classes 40 (i) and 118 (ii) [Also in Group XL(c)] In a system for recording the track of a moving object, e.g. an aircraft, whose instantaneous polar co-ordinates are determined periodically by a radar system, the position of the object is periodically plotted on a temporary plotting table and means are provided for recording on a receiving table a continuous track line corresponding to the sequence of plots, the plots being of a temporary nature. In the system illustrated the range of an aircraft is determined by aligning a mechanical cursor 2 Fig. 1 with the echo produced by the aircraft on a type A cathode-ray tube display and the bearing of the aircraft is determined by adjustment of a goniometer. An intermediate plotting table 9, Fig. 2, consists of a plotting surface, Figs. 4 and 5 (not shown), comprising an upper layer of glass or transparent plastic, an intermediate sheet of paper on whose top surface is drawn a map of the area and a lower backing sheet coated on its top surface with a layer of dark wax. A rotable arm 11 is pivoted under the table by means of a shaft 12 at a point representing the position of the radar set and the angular position of the arm is set in accordance with the setting of the goniometer by means of a servo T1, M1, the radial position on the arm 11 of a carriage 14 being controlled in accordance with the setting of the range cursor bya servo T2, M2. When the goniometer and cursor are set correctly the radar operator presses a switch S1, Fig. 1, which actuates a solenoid S2 on the carriage 14 bringing a plotting head 15 into contact with the underside of the table and thus making a mark on the map. If height indication is required the plotting head may comprise a type wheel 23 set by a motor M5 coupled to a computor (not shown). The angular movement of arm 11 may be corrected for site error by a suitably shaped cam. The radar operator repeats the above process producing sequences of plots A1, A2, A3; B1, B2, B3; C1, C2, C3, corresponding to the tracks of aircraft A, B, and C and these tracks are transmitted to a remote display table 22, Fig. 3, by an operator who moves a stylus 18, Fig. 2, along the lines of plots. The stylus 18 is mounted on a carriage 7 movable in the X direction along rails 16 which are movable transversely in the Y direction and the remote table 22 comprises a recording stylus 21 fixed to a carriage 20 mounted in a similar manner, the two tables being interconnected by servo transmitters T3, T4 and servo motors M3, M4, so that stylus 21 moves in correspondence with stylus 18. When a track has been transferred to the remote table 22, the corresponding plots on table 9 may be erased manually by means of a small sheet-steel or soft iron element sandwiched between the map and the waxed backing sheet, the element being moved along the line of plots by a magnet or the plots may be erased automatically by mounting an electro-magnet on the carriage 17 so that the erasing element follows the stylus 18. In a modification the polar co-ordinate data from the radar set is converted to rectangular form and the plotting head is carried by a carriage similar to carriage 17. In a further modification a plot may be recorded by projecting upwards a beam of light from the carriage 14, the plotting table having a fluorescent coating with sufficient after-glow to retain the individual plots long enough for a track to be determined; alternatively the light source may be fixed and the position of the plot controlled by varying the direction of the light beam.