The groundwork of practical naval gunnery; a study of the principles and practice of exterior ballistics, as applied to naval gunnery, and of the computation and use of ballistic and range tables . f one occur it must be the result of some mistake or someavoidable error). 238 EXTERIOE BALLISTICS 385. Suppose that we have as the point of aim the center, 0, of the verticaltarget screen shown in Figure 37, and suppose we had n points of impact as shown(18 are shown) of which the coordinates are (z^, y^), {z^, ^/a), {zn, yn), each with itsproper algebraic sign. Then manifestly the coordinates of t
The groundwork of practical naval gunnery; a study of the principles and practice of exterior ballistics, as applied to naval gunnery, and of the computation and use of ballistic and range tables . f one occur it must be the result of some mistake or someavoidable error). 238 EXTERIOE BALLISTICS 385. Suppose that we have as the point of aim the center, 0, of the verticaltarget screen shown in Figure 37, and suppose we had n points of impact as shown(18 are shown) of which the coordinates are (z^, y^), {z^, ^/a), {zn, yn), each with itsproper algebraic sign. Then manifestly the coordinates of the mean point of impact referred to 0 as an origin are (-^ > —^ ) , which for the 18 shot shown on the figure would place the mean point of impact somewhere near the point P. Of coursethe larger we can make n, the more accurately is the position of the mean point ofimpact determined. Then, the origin being shifted to P, we get new values of thecoordinates z and y, from which we know the deviations of each shot from the meanpoint of impact, both horizontal and vertical. The same process is resorted to in thehorizontal plane, with coordinates x and z to determine the position of the mean. Figure 37. point of impact in that plane, and thence the deviations of the several shots in thatplane. 386. Having found the position of the mean point of impact as described above,and the coordinates of the several points of impact in relation to it, we then get themean dispersion from mean point of impact in the lateral and in the vertical direc-tions by taking the arithmetical mean (all signs positive) of all the z coordinates forthe one and of all the y coordinates for the other, taking the mean point of impact asan origin. The mean dispersion from mean point of impact in the horizontal planeis determined in a similar 387. The probability of a future event is the numerical measure of our reason- able expectation that it will happen. Thus, knowing no reason to the contrar
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectballistics, bookyear1
