Patent GB-731469-A (GB)
Title: Improvements relating to baskets
IPC: D06F95/00
Filed: 1953-02-03
Abstract: 731,469. Surveying instruments. ESDAILE & SONS PTY., Ltd., E. June 1, 1953 [July 7, 1952], No. 15178/53. Class 97 (2). A surveying instrument cornprises a sighting telescope pivoted so as to be movable in a vertical plane and having a graticule of spaced lines for application of the stadia principle, a pointer or the like and a diagram having plotted thereon several points, each point being plotted at a distance from a datum level corresponding to the vertical interval between an observing and observed station, and indicia on the diagram indicative of the intercept that would be observed on a surveying staff between the stadia lines under the conditions of elevation or depression represented by each point, the diagram and pointer being arranged so that a pivotal movement of the telescope produces a relative movement in one sense between them, manually-operable means whereby such relative movement in a second sense may be produced to bring the pointer and a point on the diagram opposite one another, and indicating means carried by the manually operable means and arranged to provide an indication of the vertical interval between observed and observing stations on completion of a relative movement in said second sense. A surveying instrument comprises a theodolite having a telescope 11 supporting at 14 a telescopic device 10 including an eyepiece 15, pentagonal prism 16 and a semi-transparent mirror on which a spot of light is projected through a pin hole 18 so as to be visible in the eyepiece. Also visible in the eyepiece 15 is a chart 13 mounted on a cylinder 21 which is rotatable by knobs 24 or 25 about an axis perpendicular to the rotary axis of the sighting telescope 11. Rotatable together with or independently of the cylinder is a disc 28 bearing a scale in feet or other units of length, and a pointer 26 on knob 25 is so arranged that it coincides with fixed index mark 31, readable through a lens 32, when the telescope axis is horizontal, the spot of light on mirror 17 at this time appearing in co-incidence with a line X-X on chart 13 which represents zero altitude. Chart 13 bears a series of lines 36, 37 of which each line 36 is plotted through points representing equal intercepts on a levelling staff held vertically at several observed stations, each line being associated with a, number defining that intercept. Lines 37 are drawn through points which represent equal horizontal distances. In use, telescope 11 is set with its axis horizontal and then scale disc 28 is rotated alone until pointer 26 registers with the graduation therein representing the height of the observing station. The telescope is now pointed at a vertically held staff at the observed station and the staff intercept noted. One of the knobs 24 or 25 is then rotated until the spot of light appears to coincide with the line on chart 13 representing that intercept. The reading on scale disc 28 which registers with index mark 31 then gives the height of the observed station. The diagram may be in the form of a plane and be movable in a direction parallel to the line thereon representing zero altitude; alternatively it may be in the form of a disc, rotatable about its centre.