Bulletin of the United States Geological SurveyThe Survey., 1904 |
Table des matières
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Autres éditions - Tout afficher
Bulletin of the United States Geological Survey Geological Survey (U.S.) Affichage du livre entier - 1971 |
Bulletin of the United States Geological Survey Geological Survey (U.S.) Affichage du livre entier - 1907 |
Bulletin of the United States Geological Survey Geological Survey (U.S.) Affichage du livre entier - 1898 |
Fréquemment cités
Page 283 - This is a most generally useful stadia table for rods reading 100 feet to the foot and with angles up to 30°. The values of other measures than those given in the table are obtained by multiplying the quantities under the proper vertical angle by stadia readings in hundreds of units. The quantity representing the focal distance is very small and is given at the bottom of each page for focal lengths between...
Page 16 - In fig. 2 the full vertical line represents a portion of the meridian passing through the zenith Z (the point directly overhead), and intersecting the northern horizon at the north point N, from which, for surveying purposes, the azimuths of Polaris i I i 4 /S v sT i i Hainan L
Page 11 - ... small, the lengths of D and G are approximately computed with the angle Q. The following quantities must be known in addition to the measured angles in order to find the correction for reducing to center: 1. The angle measured at the instrument, P, between the center of the signal or station, C, and the first-observed station to the right of it, A. 2. The distance from the center of the instrument to the center of the station = r. 3. The approximate distances, D, G, etc. , from the station occupied...
Page 13 - ... fourth point, P, it is required to determine the position of P. Set up the theodolite at P and measure the two angles subtended by any two of the given sides. This problem is of use in cases where, the regular triangulation having been completed, additional points are required for the topographic survey, or are needed for special service. The angles should be carefully measured, and in the computations the logarithms should be carried to seven places of decimals. Three cases of its application...
Page 24 - Om.5 greater than printed, the table being so arranged to economize space. The table will be used as follows: Find the hours of the time argument in the left-hand column of either page; then, between the heavy lines which inclose the hours, find the m mutes in the column marked at the top with the current year.
Page 17 - In the diagram,— which the surveyor may better understand by holding it up perpendicular to the line of sight when he looks toward the pole, — Polaris is supposed to be on the meridian, where it will be about noon on April 10th of each year.
Page 107 - Areas of quadrilaterals of earth's surface of 15' extent in latitude and longitude — Continued. [From Smithsonian Geographical Tables.] Middle latitude Area in iquaremile.H.
Page 20 - B, opposite the third or seventeenth day of the month in the left hand column, will be found the correction 7m.9. Computing from a preceding date, for days between April 11 and 15 of any year, the reduction in B will be greater than the tabulated time of culmination, in which case 23" 56m.l will be added, to make the subtraction possible.
Page 267 - For obtaining differences of altitude for any minute up to 15 degrees, and for any distancc. [Prepared by Arthur P. Davis.] EXPLANATION OF TABLE. The left-hand column is the minutes of the vertical angle, the degrees being denoted by the large number at top of page. The boldface figures at top of column is the distance in miles. Numbers in the body of the table denote the difference of elevation corresponding to the angle on the left and the distance at top. The correction for curvature, refraction,...
Page 25 - XVII, near the top of the page, the surveyor will observe that for a difference of four minutes in the time argument there is a change of about two minutes in azimuth; consequently, to obtain the azimuth to the nearest whole minute of arc, the local mean time, upon which all depends, should be known within two minutes. When the surveyor uses a solar instrument, he can readily determine the time for himself during the afternoon before observing Polaris, or in the morning after observation, and, without...