GB966197A - Improvements in and relating to navigation systems for marine and like craft and apparatus therefor - Google Patents

Abstract

966,197. Electric records; navigation. LITTON INDUSTRIES Inc. Oct. 12, 1961, No. 36613/61. Heading G5R. [Also in Division H4] Errors in a dead-reckoning navigational system (e.g. a system using inertial techniques)which traces the apparent track of a navigable craft on a contour (depth profile) chart are eliminated by measuring the actual depths at selected instants and then manually adjusting the dead-reckoning system by shifting the traced track parallel to itself until the apparent depth indicated by the trace coincides with the actual depth measured at any particular instant. In the described embodiment the contour chart 32 (Figs. 2 and 3) is formed as an electrically insulating base 31 carrying electrically conductive segments 32 separated by depth contour lines 33 of insulating material and, as shown in Fig. 2, the various segments 32 are biased to respective potentials corresponding to the depths represented thereby so that in operation, an electrically conducting stylus 26 (see also Fig. 4) which is driven across the chart (the apparent track) under the control of the dead-reckoning apparatus (not shown) results via a servo balancing arrangement 42, 43, 44 in the production of a rotation of a shaft 45 in a direction and by an amount proportional to the variations in depth along the track traced by the stylus. For measurement of the actual depth a known form of echo sounder comprising a transducer 19 driven by an acoustic pulse transmitter 18 under the control of a keyer 49a is employed. This operates in known manner in response to echoes from the ocean bed 20 to supply a signal via a "print" amplifier 17 to a recording stylus 15 which traverses the width of a chart 13 at a high speed the chart being calibrated (across its width) in units of depth and driven in the direction of the arrow at a speed related to the speed of the craft by means of motor 14 which also controls keyer 49a. The actual depths are thus recorded as a trace such as 22 and to correlate the latter with the apparent depths as tracedby stylus 26 on chart 30 the rotation of shaft 45 is arranged, by means of a conducting ring electrode 46 rotating with shaft 45 and provided with an insulating portion 47 which cooperates with a brush electrode 48 driven by a scale repeater 49 via motor 14, to trigger a pulse generator 50 which supplies its output to stylus 15 via "print" amplifier 17 at instants determined by the rotary phase displacement of the circulating portion 47 with respect to the rotating brush 48. A trace such as 24 is thus produced on chart 13 which coincides with the trace 22 only if the deadreckoning apparatus is without error. When error is present the latter apparatus is corrected by adjustment of the co-ordinate drives of stylus 26 by means of controls 51, 52 (Figs. 2 and 4) until the two traces coincide. U.S.A. Specification 1, 785, 241 is referred to.