A Treatise on Surveying; Comprising the Theory and the Practice Volume 2

A Treatise on Surveying; Comprising the Theory and the Practice Volume 2

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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. 1897 edition. Excerpt: ... refraction in several localities. Observations were made hourly for a number of days (more than ten, with few exceptions). The value for each hour as plotted is the mean of all the observations made at that hour during the days of observation. Curve A is the result of observations made at Ragged Mountain, Me., during July, August, and September. Curve B, the result of observations at Martinez East, near Straits of Carquines, California. Curve B', at' Mount Diablo, California. Curve C, the mean of the results at Bodega Head and Ross Mountain, on the coast of California, about fifty miles north of San Francisco. Owing to the excessive moisture on the Pacific coast the refraction is greater and more variable than east of the Sierra Nevada Mountains, as is distinctly shown by these curves. B and B' were obtained from observations at opposite ends of the same line, B being at an elevation of about 57 metres, and B' about 1,173 metres above the sea level. B and B' show that the refraction is much larger and more variable at low elevations than at high, and that the changes are in practically the same direction. When to Observe.--Experience has shown that the best results for double zenith distances are obtained by making the observations CURVES SHOW1NG D1URNAL VAR1ATION OF COEFF1CIENT OF REFRACTION at about noon or 1 P. M.--i. e., during the period of minimum refraction. Two sets, as mentioned above, are usually sufticieut to get the zenith distance on any one day. As the refraction is very different on different days, observations must be made on a number of days in order to get the zenith distance for an average refraction. In mountain work, with long lines, it has been found that ten or fifteen days' observations are necessary, and that it is not...show more

Product details

  • Paperback | 122 pages
  • 189 x 246 x 7mm | 231g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236605063
  • 9781236605061