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 381
by the ordinaryrule of nautical astronomy, the true bearing of the object isfound by applying the mean of the theodolite angles of that set,Methodby In finding a true bearing with sextant only, it will be moreaccurate if two observers are employed—one to take thealtitude, the other to measure the… … observation as that with which he begins, so that the mean ofeach kind will correspond as nearly as may be in time. Thus,if he begins with altitude, he must also end with altitude. This method should not, however, ever be used when atheodolite is available, and is only adopted for true bearingsfrom…
Hydrographic surveying · Nautical charts
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