Patent GB-1016260-A (GB)
Title: Meridian and latitude indicator
IPC: G01C1/02
Filed: 1963-02-04
Abstract: 1,016,260. Meridian and latitude indicators: gyroscopic apparatus. ASTRO-SPACE LABORATORIES Inc. Feb. 4, 1963 [Feb. 13, 19621, No. 4461/63. Headings G1C and G1F. [Also in Division H4] An apparatus that may be used to indicate the meridian and the latitude of its location, at any non-polar location on the earth's surface comprises a gyroscope having a rotary cup 4 driven about a vertical axis by a motor 2, and a spherical rotor 5 mounted on a gas bearing in the cup 4 and rotated by rotation of the cup, the spin axis of the rotor being tilted from the vertical in the eastwest plane due to the rotation of the earth, means being provided to indicate the orientation of the east-west plane and thus the meridian, the degree of tilt, which is a junction of the latitude of the non- polar location. The movement of the cup 4 due to the rotation of the earth exerts a torque on the rotor 5 which precesses so that its axis of rotation is tilted in the east-west plane by an angle which is dependent on the latitude. The cup 4 and rotor 5 are mounted inside a housing 1 rotatable in the horizontal plane. The tilting of the axis of rotation of the rotor 5 is observed by use of an optical system, Fig. 6, comprising a lamp 14 light from which is reflected by mirrors 16,18 and collimated to pass through a prism 22 which is in the form of a truncated four sided pyramid with its four side surfaces silvered. The light is then reflected by mirrors 24, 28 and passes by way of a lens 26 to a mirror 30 mounted on the axis of rotation of the rotor 5. If this mirror is not displaced then the light passes back along its original path and through the truncated end 20 of the prism 22, no light being reflected by the side faces of the prism. If however the mirror 30 is displaced in the east-west plane then light will fall on the mirrored surface 34 of the prism 22, Fig. 7A, and this light is reflected to a photo-cell giving an output fed to an amplifier 37, indicative of the latitude of the position of the apparatus. This signal may be fed to a remote latitude indicator 68 Fig. 1. Further, if the surface 34 and the one opposite to it are not aligned in the east-west plane i.e. if the apparatus is turned through an angle in the plane of Fig. 7A the light from the mirror 30 will also fall on the mirrored surface 38 on the one opposite and thus on a photo-cell 40, or 41 giving an output from an amplifier 46 which is either fed to a computer connected to a compass course indicator 48 in the form of a voltmeter pointer and compass card, or to a computer controlling an automatic pilot. Alternatively, and as in the apparatus of Fig. 1, the output of the amplifier 46 is used to drive a motor 52 to rotate the housing 1 to reduce the signals from the photo-cells 40, 41, and thus to maintain the apparatus aligned with the surface 34 and the opposite one in the eastwest direction. In this condition a voltmeter 50 gives a zero reading. The housing carries a compass card 53 and a fixed pointer (not shown) is provided to indicate the compass bearing. This bearing may also be indicated on a remote compass card 70 by a pointer 100, by use of a synchronous transmitter 74 and receiver 72. The bottom 76 of the housing 1 is maintained level in a vehicle by mounting the housing in gimbals, as 82, the centre of gravity of the housing being disposed below the normal plane of the gimbals, and if desired, level indicating devices 88 may be provided which control motors as 90 to provide positive levelling. The gimbals may be dispensed with if the apparatus is to be used on land, normal levelling screws being provided. A theodolite 62 is mounted on the housing, and when sighted on a remote object a pointer 62 gives the compass bearing of the object on a compass card 64. The theodolite is controlled by a handwheel 58.