GB289872A - Improvements in the method of and apparatus for determining the instantaneous position and the speed and direction of movement of invisible air craft by exclusively acoustic means - Google Patents

Abstract

289,872. Akt.-Ges. C. P. Goerz Optische Anstalt. May 6, 1927, [Convention date]. Gunnery calculators. -The path of an aircraft is acoustically determined by means of three observation stations on the ground at which sounddirection locators, as shown in Fig. 1 are provided to observe the inclination to the horizontal of three planes passing through two near consecutive positions of the horizontally-flying craft and the common azimouth of the intersection of these three planes with the horizontal at the three observation stations. At one station, chosen as the central base station, a graphic calculating framework, shown in Fig. 3, is employed for reproducing mechanically the horizontal projection of the base triangle from which the height of the aircraft is obtained. The approximate height so obtained is used as a setting on a second graphic instrument, shown in Fig. 8, for giving the displacement of the sound source and the change of the lag of sound during the measuring period. From the results given by this instrument a third instrument, shown in Fig. 13, can be set to give the velocity of the aircraft, and the various data thus determined are set upon a spherical instrument shown in Fig. 14, fitted with setting circles mounted upon an axis 6, Fig. 1, of the central acoustic instrument, and give a directing sight line towards the instantaneous position of the aircraft. The sounddirection locators comprise a horizontal direction pair of paraboloidal reflectors 1, 1<1>, the foci of which coincide with the foci of long ellipsoidal reflectors 2, 2<1> having their other foci at the listening point. A vertical direction pair of paraboloidal reflectors 9, 9<1> are similarly connected by coincident foci through ellipsoids 10, 10<1>, 11, 11<1> with the second listening point. Horizontal and vertical reading circles 4<c>, 18' are provided. On the first graphic instrument the horizontal plan of the three observing stations is set at A (the central station), Fig. 3, Band C by their azimuths on a circle 32 by radial arms, the azimuth circle being set according to the common azimuthal direction of the horizontal intersection with the three planes of observation, so that the vertical pointer 31<a> corresponds to the direction of flight of the aircraft. The radial settings for the stations B. C give projected m the base G of the instrument the horizontal settings for the centres of semi-circles 45, 45<1>, the vertical heights of which are set to the different levels of the two outlying observation stations, the centre 46 corresponding to the central station being fixed. Sliders 47 with radial wires 48 are set to the observed angles of inclination, acoustically found, of the three planes, and a sighting aperture 50b, by observing the crossing-point of the wires, gives a reading on a scale 49 of the height of the sound source. This height is set on the ordinate arm 57b, Fig. 8, the radial arms 55, 61 being set by the azimuth and altitude read from the scales 4<c>, 18<1> of the sound locators. Readings of the movement of the sliders 57<a>, 60<a> during the measured time of the two consecutive positions of the aircraft give the displacement of the acoustic source and the lag of sound, which are then set on the third instrument by means of scales 66a, 65a respectively, from which instrument the scale 62<a> gives the speed of the aircraft. This speed is set on a scale controlled by gearing 76, 78, Fig. 14, in a pivoted yoke carrying a tracer 74, the yoke also being controlled by an arcuate arm 15 from the altitude circle. The line through tracer 74 and the centre of the sphere gives the instantaneous direction of the aircraft. A pointer 88<c> and an arm 90 may be used to communicate the direction to a searchlight or other instrument. Fig. 14 shows the correct disposition of the hemisphere inscribed by the tracer 74, this being shown inverted in Fig. 1 so as to avoid obscurity.