An Improved Instrument for Determining on a Map the Position of an Object in Relation to, and its Distance from, any Given Point.

摘要

122,087. Kennedy, J. F. March 22, 1918. Gunnery calculators.-An instrument for determining on a map the angular and distance relations of an object with reference to a given point, such as a gun position, comprises a strip of transparent material marked with a scale of distances b equal to the range of the gun the zero end c of this scale forming an axis upon which the instrument is rotated, whilst the upper end of the strip is arc-shaped concentrically with the axis and is provided with two similar degree scales d, e which terminate at the opposite edges of the instrument, and are so disposed thereon that by scribing at the end of each scale on the movement of the instrument to the right or left the line thus made above or below the determined arc facilitate the correct reading of angular position of the target. The arc is drawn by inserting a pencil, in a hole v and then rotating the instrument, reference lines O.R. (zero right) 10 degrees R, &c. it will be observed will fall outside the circle and lines O.L. (zero left), 10 degrees L &c. will fall inside the circle. Alternatively large arcs may be graduated by means of an arc s intersected by radial lines t, 10 degrees apart, at the ends of which are holes t' through which a pencil may be passed. Scales m, n indicate (a) the angles of sight at the various ranges of targets whose heights are 5 and 15 metres respectively above the observer, or (b) the concentration or distribution for parallelism of guns in a battery placed 5 and 15 metres apart respectively and aimed at targets having the ranges given on scale b. Scale x is divided into half-inches and is graduated in degrees, and in use is held at arm's length to determine the angle subtended at the eye by two distant points. Map grids are shown at o, p, q.