Patent GB-343483-A (GB)
Title: Improvements in long base height and range finders
IPC: F41G5/00
Filed: 1929-11-14
Abstract: 343,483. Range-finding apparatus. BARR & STROUD, Ltd. and FRENCH, J. W., Caxton Street, Anniesland, Glasgow. Nov. 14, 1929, No. 34784. [Class 97 (i).] Direction control systems of the long base type for the determination of heights and ranges are provided with means whereby the target observed by the main station at one end of the long base can be brought into the field of view of the sighting device at the second station at the other end of the base, together with means for the accurate determination of heights and ranges of the target accurately observed thereafter by both stations. The angle of sight A, Fig. 1, in a vertical plane normal to the base is first determined, this angle being common to the two stations and is then communicated to the second station 2 together with a second angle derived from an estimated or separately determined height or range at the first station 1, such angle being e.g. the angle C between the base line and the line of sight to the target 3 at the second station 2, so that the accurate determination of heights or ranges may be made from observations at both stations 1, 2. The angle C at the second station 2 may be determined from the height 3, 4 and the measured angle A, these dimensions giving the length of the line 3, 5 which is perpendicular to the base 1, 2. The values of the angle B and the range 1, 3 are also known, from which the value of the angle C may be determined. These various determinations may be performed by optical means described in Specifications 287,608 and 289,926, [both in Class 97 (i), Optical systems &c.]. The values of the angles A, C having been communicated to the observer at station 2 the correct target may be simultaneously observed and the two observers co-operate in obtaining the accurate data required. A sighting device for obtaining the values of angles A, B, C comprises a right-angled prism 6, Figs. 4 and 5, by which the target is viewed through the eye-piece 11, objective 9 and prisms 10, 8, 7. The prism 6 is rotatable by a worm-wheel 12 from the hand-wheel 14 at the same time as the prism 8 is rotated at half the rate so that the image of the target remains erect in the eye-piece 11. The movement of the handwheel 14 gives the value of the angle B. To obtain the value of the angle A the whole apparatus is rotated bv the hand-wheel 19 and the worm-wheel 17. At the main station 1 is arranged a sighting device 21 and a computing device 22, as shown in Fig. 6, and a sighting device 23 is arranged at the second station 2. The sighting devices are of the kind shown in Figs. 4 and 5. Instruments for the reception and transmission of data of the kind described in Specification 301,127, [Class 40 (i), Electric signalling systems &c.], are associated with the sighting device 23 and the computing apparatus 22. In operation, the sighting device 21 is rotated about its trunnion to determine the angle A which is transmitted by the electrical connection 25 to the computing apparatus 22. The handle 26 rotates the top prism 6 in the plane of sight 1, 2, 3, Fig. 1, to determine the angle B, which is communicated by the connection 27 to the apparatus 22, and the length of the base is set on the scale 29 by the handle 28. The estimated or measured value of the height is set on the scale 31 by the handle 30. A single eye-piece 52 having the field of view shown in Fig. 7, adapted to combine the three adjustments, is used in conjunction with optical computing apparatus as described in Specifications 287,608 and 289,926. By displacement of the mark 32 until it coincides with the index line 33 the length 3, 5 of the triangle 3, 4, 5 is determined. Similarly coincidence of the marks 36, 38 with the index line 33 give the range 1, 3 and the value of the angle C by the rotation of the handles 35, 37 respectively. Angles C, A are communicated to pointers 39, 40 respectively of a long-distance transmitter. Setting the pointers 41, 48 opposite the pointers 40, 48 moves pointers 43, 49 at the second station. The sighting device 23 is then set on to the correct target by handles 44, 50 which move the device 23 and the prism 6 and also the hands 45, 51 to positions opposite pointers 43, 49. Should the height 1, 3 only have been determined approximately the image of the target will not lie accurately on the reference mark in the sighting device 23. Readjustment by the second observer by the handle 50 is indicated at the first station by moving the pointer 49 to coincide with the new position of pointer 51 by the handle 46. This displaces pointer 48 and readjustment of pointer 39 by handle 47 moves the mark 38 in the eye-piece 52. Rotation of the head 35 restores the mark 38 to coincidence and indicates the true value of the height on the scale 31. This affects the position of the mark 36 which is restored by movement of the handle 34 giving the true value of length 3, 5, and angle A. The optical means for adjusting the images of the marks 32, 36, 38 in the plane 60 of the eye-piece 52 is shown in Fig. 8, and comprise a series of deviating prisms capable of rotation and/or translation by the rotation of the various handles of the completing apparatus 22, Fig. 6.