Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ... C. Surveyors take advantage of this principle to check the transit work, considering a close in arc, as it is termed, to be within one minute for good work. The course A B, with respect to which the azimuths are taken, is called the meridian of the survey. 1182. In finding the area of a piece of ground, it is not necessary to know the magnetic bearings of the courses. It is sufficient to have the bearings of the several successive courses with respect to one of the courses taken as a meridian. These may be found from the azimuths, determined as above, in the following manner: Let us suppose that the course taken to start with is a north and south line. We will consider this course as the meridian to which the azimuths of all succeeding courses will be referred. Let the course A B, Fig. 218. be taken as this meridian. The azimuths of the succeeding courses are found by the transit, by the method already described, to be as follows: The azimuth of A B referred to A B = 0. The azimuth of B C referred to A B = 70, angle turned to the right. 11 ' The azimuth of C D re ' ferred to A B = 150, angle turned to the right. The azimuth of D E re"% ferred to A B = 265, angle-turned to the right. The azimuth of E A referred to A B = 288, angle turned to the right. In order, now, to reduce these azimuths to the bearings of the courses, we must bear in mind that these azimuths were obtained by turning off angles to the right by means of the vernier. In Fig. 219, the vernier is conceived as moving in the direction of the hands of a watch. It is plainly seen from it that: When the azimuth is 0, the course is due north. When the azimuth is between 0 and 90, the course lies in a N E direction. When the azimuth is exactly 90, the course is due east. When the azimuth is be...
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