. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. mple, suppose that we have the following bearings anddistances, which enclose a space represented by ABCD. Bearings. Distances. AB °E. - - 17 BC KZZ°E. - - 11 CD °E. - - 23 DA tf. 77° TT. - - - SURVEYING. Let JVS represent the meridianrunning through A, the most westernpoint of the field ; make the angleJVAB=23°, and AB=\1; then Abis the latitude, and Bb is the depart-ure, corresponding to the courseAB. By means of the right angledtriangle ABb, having
. A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects. mple, suppose that we have the following bearings anddistances, which enclose a space represented by ABCD. Bearings. Distances. AB °E. - - 17 BC KZZ°E. - - 11 CD °E. - - 23 DA tf. 77° TT. - - - SURVEYING. Let JVS represent the meridianrunning through A, the most westernpoint of the field ; make the angleJVAB=23°, and AB=\1; then Abis the latitude, and Bb is the depart-ure, corresponding to the courseAB. By means of the right angledtriangle ABb, having the hypotenuseAB, and the angles, we can com-pute Ab, and Bb, , and ,or we can turn to the traverse table,and under 23° and opposite 17, weshall find the value of these lines atonce ; and this is the utility of having the traverse table. In the same manner we find Bm and m C, the latitude and depart-ure corresponding to the bearing and distance of the line BO. Wefind Bm=, and m (7= Thus we go round the field, taking the latitude and departure ofeach side, and arrange the whole in a table as follows:. Bearings. 2323,66 N. 22,32 E. ~676~4 10,92 5,56 23712 w. 23,0523,05 ABBCCDDA JV. 23° E-N. 83°^.S. 14° J2- K 17° W- 15,651,34 5,33 22,32 22, 32 When the several operations are performed with perfect accuracy,the sum of the northings will be equal to that of the southings, andthe sum of the eastings to that of the westings. This necessarilyfollows from the circumstance of the surveyors returning to theplace from which he set out; and it affords a means of judging ofthe correctness of the work. But it is not to be expected that themeasurements and calculations in ordinary surveying will strictlybear this test. If there is only a small difference, as in the aboveexample, between the northings and southings, or between the east-ings and westings, it may be imputed to slight imperfections in themeasurements. Here the northings and southings agree, b
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Keywords: ., boo, bookcentury1800, booksubjectnavigation, booksubjectsurveying
