GB494252A - Calculating devices for navigating purposes - Google Patents

Abstract

494,252. Calculating - apparatus. STANDARD TELEPHONES & CABLES, Ltd. April 23, 1937, No. 11686. Convention date, May 2, 1936. [Class 106 (i)] A calculating-device for solving navigation problems comprises three coaxial relatively rotatable discs carrying scales relating respectively to geographical meridians, to magnetic meridians and to bearings obtained by radio, a cursor arm being fixed to the last-named disc and a further independent cursor arm being movable over all the discs. The disc 1 relating to geographical meridians has scales 2, 5 and an arrow (not seen) at the zero of scale 2. The disc 6 relating to magnetic meridians has scales 7, 8 and the arrow on disc 1 is set to indicate on scale 8 the magnetic declination. The cursor line 18 on the independent cursor 17 then indicates the true route on scale 2 of disc 1 and the corresponding compass course on scale 7 of disc 6. A disc 10 is set so that the bearing obtained by radio is indicated by a scale 11 on disc 10 reading against cursor line 18. The cursor 24 fixed to the disc 10 indicates the corresponding compass and true bearings on discs 6 and 1 respectively. A series of inclined lines 23 is marked on a transparent part of the cursor 17 and a set of inclined lines 15, Fig. 4, is provided on the margin of the disc 10, these latter lines leading from each radio bearing graduation 11 at an angle corresponding to a correction to be applied to that radio bearing. The disc 10 may have a second scale 12 which is used in drawing the lines 15 from given data, the scale 12 then being detached at a perforated line 13. When a radio bearing is being set on the device of Fig. 5, the disc 10 is adjusted until the graduation 11 denoting the bearing is positioned so that its inclined line 15 is beneath a line 23 of the same slope. The desired correction is thus incorporated. The back of the device has printed upon it a circularly-arranged table of coefficients, each coefficient defining the ratio of the sine of a first radio bearing to the sine of the difference between said first bearing and a second radio bearing. The Specification describes how these coefficients enable the distance from the radio transmitting station to be determined. The Specification states that the discs 6, 10 may be connected to a compass and a radio direction-finder respectively.