Patent GB-849500-A (GB)
Title: Improvements in and relating to navigating apparatus for radar data presentation
IPC: G01S7/04
Filed: 1956-11-19
Abstract: 849,500. Radar. ATLAS-WERKE A. G. Nov. 19, 1956 [Nov. 19, 1955; May 18, 1956], No. 2725/60. Divided out of 849,499. Class 40(7). [Also in Groups XIX and XX] Relates to a ship-borne pulse radar with a short-persistence cathode-ray tube plan-position display (P.P.I.) comprising means for plotting on a record surface the track of the carrier ship i.e. the ship carrying the radar, and the tracks of the other craft in its vicinity, the record surface being controlled selectively to provide either (1) a "relative" display, i.e. displayed instantaneous heading of the ship maintained in a fixed reference direction, e.g. vertically upwards when the record surface is in a vertical plane or (2) a "true" display, i.e. predetermined geographical direction, e.g. north, as represented on the record surface maintained in the fixed reference direction. According to the present invention the P.P.I. display 1 is projected optically onto the surface of a sphere 4 mounted on rollers 8 permitting rotation of the sphere in any direction. The sphere is rotated about a horizontal axis in accordance with the speed of the ship by means of a pair of friction wheels 10, 11 pressed resiliently against the bottom surface of the sphere as shown in Fig. 2 and driven in unison by means of a differential gear 27, Fig. 3, and a synchro motor 26 controlled by the ships log. The sphere 4 is also rotated about a vertical axis in accordance with changes in the ships heading by driving the wheels 10 and 11 in opposition from a compass repeater 28 via gearing 29-33. The wheels 10, 11 and their driving means are mounted on a plate 13 carried by a shaft 14, Fig. 2, coupled through a clutch 18 to a compass repeater 19. The images projected onto the surface of the sphere may be recorded thereon (1) manually by means of a pencil or (2) by coating the surface with a long-afterglow fluorescent material to give a luminous record which may be erased by an annular heater 9 concentric with an annular mask 6 surrounding the area on to which the P.P.I. image is projected. For a "relative" record display, the clutch 18 is disengaged and the plate 13 is locked in a position such that the axis 12 of the friction wheels 10, 11 is perpendicular to the fixed reference direction. For a "true" record display, the clutch 18 is engaged so that the axis 12 of the friction wheels 10, 11 is oriented in accordance with the ships heading; a change in heading does not now produce a corresponding rotation of the sphere 4 about a vertical axis since the rotation effect of the differential drive on the friction wheels 10, 11 is compensated by the rotation of the axis 12. In either mode of operation the bearing of objects from the carrier ship may be determined by a cursor line on a glass plate 7 rotatably mounted in the mask 6. When it is required to produce a "true" record display only, the sphere may be driven by two friction wheels having shafts orthogonally disposed in the plane of the equator of the sphere, the wheels being rotated in accordance with the north-south and east-west components of the ships motion.