Stadia Surveying: The Theory of Stadia Measurements

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D. Van Nostrand, 1884 - 148 pages
 

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Page 52 - ... for every 2 minutes, when ak — 100. To obtain the horizontal distance or the difference of level in any case, the corresponding value of c cos n or c sin n must further be added; and the mean of each of these expressions, for each degree, with three of the most common values...
Page 18 - ... for an instrument having any constant (c). Similar tables have been computed by JA Ockerson and Jared Teeple, of the United States Lake Survey. Their use is, however, limited, from the fact that the meter is the unit of horizontal measurement while the elevations are in feet. The bulk of the tables furnish differences of level for stadia readings up to 400 meters, but only up to 10° of elevation. Supplementary tables give the elevations up to 30° for a distance of one meter. For obtaining horizontal...
Page 18 - ... it was thought sufficient to determine these values only for each degree. As c varies with different instruments, these last two expressions were calculated for three different values of c, thus furnishing a ratio from which values of c sin n and c cos n can be easily determined for an instrument having any constant (c). Similar tables have been computed 'by JA Ockerson and Jared Teeple, of the United States Lake Survey. Their use is, however, limited, from the fact that the meter is the unit...
Page 52 - 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 to the stations observed. The latter may be computed from the uncorrected angles. Example: Reduction to center from P to C. Constants: ac log sin 1
Page 18 - As c varies with different instruments these last two expressions were calculated for three different values of c, thus furnishing a ratio from which values of c sin n and c cos n can be easily determined for an instrument having any constant (c). Similar tables have been computed by JA Ockerson and Jared Teeple, of the United States Lake Survey. Their use is, however, limited, from the fact that the meter is the unit of horizontal measurement while the elevations are in feet. The bulk of the tables...
Page 50 - The dill'erence may be due, perhaps to some cause which I did not consider, such as a slight leaning of the rod forward or backward, inexactness in placing the face of the rod precisely at the station, imperfect graduation of the rod, imperfect cleanliness or transparency of the glasses or of the air, imperfection in the shape of the lenses or in their adjustments to one another, inferior lighting of the magnified...

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