Patent GB-441247-A (GB)
Title: Improvements in or relating to navigating instruments
IPC: G01C21/02
Filed: 1935-05-16
Abstract: 441,247. Latitude and longitude instruments. HAGNER, F. H., 1021, Navarro Street, San Antonio, Texas, U.S.A. May 16, 1935, No. 14390. [Class 97 (ii)] Apparatus for determining latitude and longitude is provided with an azimuth circle, means within and in the same plane as the azimuth circle to receive a ray of light from a celestial body, and an altitude arc adjustable around the axis of the azimuth circle and carrying an adjustable altitude indicator. An hour arc adjustable around a diameter of the azimuth circle in accordance with the latitude and around a perpendicular axis in accordance with the hour angle may be provided. In the form shown a gimbal ring 10 is pivoted to the support 3 on bearings 11 and carries journals 12 for pivot pins 13 carried by suspension rods 14. A platform 18 secured to the rods 14 by arms 15 supports by struts 19, 21, a disc 20 carrying a graduated ring 22. An azimuth plate 25 is rotatably mounted in the disc 20 and has a worm wheel 35 engaged by a micrometer screw 39. A spirit level 27, illuminated from below by a lamp 27a, has a central reflecting spot and may be either fixed at the centre of the plate 25 or eccentrically mounted in a plate 29 having a reflecting surface and rotatable. about an eccentric point in the plate 25 to bring either the level 27 or the point of intersection of a pair of lines marked on the plate 29 to the centre of the plate 25. A graduated altitude arc 40 is fixed to the plate 25 and has a toothed periphery to enable a slide 43 to be traversed over the arc by a micrometer screw which may be rocked out of engagement to effect a coarse adjustment. The plane of the altitude arc 40 is offset from the centre of the plate 25 so that a sight tube 45 mounted on the side of the slide 43 and adapted to cast light from the observed object onto the central reflecting spot may move in a plane through the centre of the plate 25. The graduated ring 22 carries bearings 70 for hanger arms 73 supporting a frame 74 on which are fixed arms 81 pivotally supporting an hour angle arc 42 in bearings 80, 83. A slide 44 similar to the slide 43 and carrying a sight tube 46 is adjustably mounted on the arc 42 and the latter is fixed to toothed graduated sector 77 engaging a micrometer screw 75 carried by the frame 74 so that the arc 42 may be adjusted about the axis 80, 83 in accordance with the hour angle of the observed body. The journal 80 may be bored as at 94 so that a sight may be taken on the pole star. A toothed graduated sector 89 engaged by a micrometer screw 86 and pivoted to the disc 20 is fixed to the frame 74 so that the latter and with it the bearings 80, 83, and arc 42 may be adjusted about the axis 70, 70 in accordance with the latitude. Methods of using the instrument for determining latitude and longitude without calculation are described. Lateral drift may be determined by placing a chart marked with concentric circles at the centre of the plate 25, projecting light from an observed object on to the centre of the chart through the tube 46 and noting the wander of the projected image. In a modification an inverted hemisphere carrying on the inside a light sensitive surface marked with lines of latitude and longitude is fixed to the under side of the graduated ring 22 and the central reflecting spot is replaced by an aperture through which light passes and records the observation photographically. For recording the inclinations of the supporting craft at the time of an observation, a dished plate depending from the disc 20 carries on its outer surface a recording sheet adapted to be marked by a punch pin mounted in the main support of the apparatus.