The Field Manual; A Practical Treatise of Surveying Methods and Operations, Embodying Field Problems for Use in Surveying Courses in Colleges and Universities

The Field Manual; A Practical Treatise of Surveying Methods and Operations, Embodying Field Problems for Use in Surveying Courses in Colleges and Universities

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ... at a point on the earth's surface and l the other at its centre. It is the correction to be (invariably) added to observed altitudes, in order to reduce. such to their corresponding values at a point of observa 1 lion at the earth's centre. Only the sun, moon, and ' planets have parallax. Fixed stars, being infinitely ' 1, distant, have no appreciable parallax, except in a few ' instances, where the parallax is measured by assumlng The sun's horizontal parallax is given for every tenth day of the year on age 1 of the N.A. That of the moon appears in column 6 of able III of each month. (Here the equatorial, or longest, diameter of the earth is considered, so that, when great accuracy is desired, the equatorial parallax must again be reduced by a correction for latitude.) ' The sun's parallax in altitude is tabulated, the variation being sensibly constant. (See Chambers' Tables.) It is often computed approximately from the formula Pa = P, ' cos a, where 11 is the apparent altitude, and.I'a and Ph respectively the parallax in altitude and the horizontal parallax, which latter (though slightly variable) is frequently taken as 8-7," which is the ratio of the earth's radius to the sun's distance. (The foregoing equation is easily derived by drawing the sensible horizon in Fig. 261 at the earth's surface instead of the observer's eye, thus removing the exaggeration made in illustrating various terms and certain distinctions, such as sensible and visible horizons.) The parallax in altitude P'I of the moon at an apparent altitude (1 may be computed from its horizontal parallax Ph by means of the formula: Sin P'I = C05' ('gin P, '. (See...show more

Product details

  • Paperback | 236 pages
  • 189 x 246 x 13mm | 426g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236889819
  • 9781236889812