The theory and practice of surveying. Designed for the use of surveyors and engineers generally, but especially for the use of students in engineering (1886)
Johnson, J. B. (John Butler), 1850-1902 · New York, J. Wiley & sons · leaf 551
dnegative when south. 520 SURVEYING. In Fig. 145 P is the pole ; Z is the zenith of the observer ; 5 is the star ; Then R. A. star = VPS = arc VB; Dec. star = SB. These coordinates are fixed, varying only by slow changesdue to the shifting of the reference-plane. Another system of coordinates is… … FlG. 145. lar to the equator. Hour-angle will of course be constantlychanging each instant. In Fi^. 145 hour-angle = ZPS. 383. Time.—The motion of the earth on its axis is perfect-ly uniform. We obtain, therefore, a uniform measure of timeby employing the successive transits of a point in the…
Surveying
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