Hydrographical surveying : a description of means and methods employed in constructing marine charts (1920)
Wharton, W. J. L. (William James Lloyd), 1843-1905, Field, Arthur Mostyn, 1855- · London : J. Murray · leaf 455
theperpendicular for each particular depth other than 100 feet;and a calculation is thus necessary to find the position for themarks on the depth-line so that it may show the perpendiculardepth over the roller. Fig. 91 shows the problem of thecalculation, which, as will be seen, is a simple one. It… … CHAP, XX.] ROLLER SOUNDING 427 the lower booms as low as possible, and the block for the depth-Une as high as possible, in order that the horizontal travel ofthe roller from the 100-foot perpendicular position may be assmaU as possible. Fig. 91. A.^mcnt.as ^el Q (Block on sounding spar) fore boom)…
Hydrographic surveying · Nautical charts
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