Surveying & field work; a practical text-book on surveying, levelling & setting-out - Brossura

Williamson, James

Brossura

ISBN 10: 1232125938 ISBN 13: 9781232125938

Casa editrice: RareBooksClub.com, 2012

Riassunto

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. 1915 Excerpt: ...appropriate lengths for the sides of the triangles being 2,000 to 5,000 ft. Precautions to Ensure Accuracy.--As regards the shape of the triangles the equilateral form will give the best results, and the practical rule is to have no angle of a triangle less than 30, which, necessarily also means that no angle can be greater than 120. The length of one side of a triangle being known the observation of the two adjacent angles will enable the lengths of the remaining sides to be calculated. It is not necessary to read the third angle of the triangle as its value can be found by deducting the sum of the other two from 180, but the reliability and accuracy of the work will be enhanced by reading the three angles separately. If their sum is found to differ by a slight amount from 180 a correction equal to one-third of the difference should be added to or subtracted from each angle so as to obtain adjusted values which will add up exactly to 180. Many of the stations in a triangulation, such as point C (Fig. 164) will form the common apex of several surrounding angles. The sum of the angles around any such station is equal to 360, and where any slight discrepancy is found in summing up the observed values a suitable correction must be applied. Calculation of Lengths of Sides of a Triangle.--The calculation of the lengths of the sides is accomplished by the aid of simple trigonometry. In any triangle, such as ABC (Fig. 163), the following relationship exists between the lengths of the sides and the sines of the angles:--a b c sin A sin B--sin C so that c sin A,. c sin B a =--:--;=;-and o =--:--sin (J sin C If, therefore, the angles A, B and C, and the length of side c are known, the lengths of sides a and b can be calculated from the above formulas. Logarithms must...

Dettagli dell?edizione

• Editore: RareBooksClub.com
• Data di pubblicazione: 2012
• ISBN 10: 1232125938
• ISBN 13: 9781232125938
• Rilegatura: Copertina flessibile
• Lingua: Inglese
• Numero di pagine: 118
• Contatto del produttore: non disponibile