A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . AD X AE (208) Quadrilaterals. In the case of a four-sided field, whose sides cannotbe measured^ or prolonged, but whosediagonals can be measured, the areamay be obtained thus. Measure thediagonals AC and BDj and also theportions AE, EC, into which one ofthem is divided by the other. Calcu-late the area of the triangle BCE^by the preceding m
A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . AD X AE (208) Quadrilaterals. In the case of a four-sided field, whose sides cannotbe measured^ or prolonged, but whosediagonals can be measured, the areamay be obtained thus. Measure thediagonals AC and BDj and also theportions AE, EC, into which one ofthem is divided by the other. Calcu-late the area of the triangle BCE^by the preceding method, or any [^of those heretofore given. Then the area of the Quadrilateral ^ f ^^^ABCD = areaofBCExd£^S2. :-^rJ^r z.!?,^^^-*^. BE X CE 7-^^ Methods for obtaming the areas of mac- x P/> (209) Polygons. cessible fields of more than four sides, have been given in Arts. OOl,) &c. nr. r-. -^- . — ,-1 - - FAUT LIT. COMPASS SURVEYING; OR By the Third 3Iethod. CHAPTER I. A^G^LAR SURVEYDG L\ GENERAL. (210) Angular Surveying determines the relative positions ofpoints, and therefore of lines, on the Third principle, as ex-plained in Art. (7), which should now be referred to (211) When the two lines which form an angle lie iii the samehorizontal or level plane, the angle is called a horizontal angle* When these lines he in a plane perpendicular to the former, theangle is called a vertical angle. \Yhen one of the Hnes is horizontal and the other line from theeye of the observer passes above the former, and in the same ver^tical plane, the angle is called an angle of elevation. WTien the latter line passes below the horizontal hne, and in thesame vertical plane, the angle is called an angle of depression. When the
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
