Engineers' Surveying Instruments, Their Construction, Adjustment, and UseJ. Wiley & Sons, 1892 - 391 pagina's |
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Engineers' Surveying Instruments, Their Construction, Adjustment, and Use Ira Osborn Baker Volledige weergave - 1892 |
Engineers' Surveying Instruments, Their Construction, Adjustment, and Use Ira Osborn Baker Volledige weergave - 1893 |
Engineers' Surveying Instruments, Their Construction, Adjustment, and Use Ira Osborn Baker Geen voorbeeld beschikbaar - 2015 |
Veelvoorkomende woorden en zinsdelen
accuracy accurate adjustment alidade altitude aneroid average error azimuth back-sight barometer barometric formulas chain chain-man clamp computed correction cross hairs declination determine difference of level direction distance dumpy level elevation eliminated engineering equal equation eye-piece fastened feet fore-sight formula gradient graduation horizontal axis inch instrument intercept justment latitude length of sight lens limb line of collimation line of sight magnetic magnetic declination magnifying power measured mercury meridian method motion move needle Notice object object-glass observations optical center ordinary parallax parallel perpendicular plane table plate plumb-bob polar axis position precision probable error refraction rings rod-man scale self-reading rod shown in Fig side slide solar compass solar telescope solar transit source of error spirit level stadia hairs station steel tape surface tangent screw target tele temperature tion tripod tube turning points U. S. Coast vernier vertical axis vertical circle zero
Populaire passages
Pagina 296 - The instrument can then be hung up and readjusted. The tube and its contents having been undisturbed, the instrument should read the same as before. If a little mercury has been lost during the operation, and there is none at hand to replace it, no serious harm has been done; but if much is lost, the open end of the tube may become exposed in inverting the instrument, in which case air may enter.
Pagina 303 - ... altitude, whether fixed or movable, and calculate the heights. § 60. Defects. — The aneroid is a very convenient instrument and for a stationary instrument where nice readings are not required, it does very well ; but for accurate hypsometrical results it is an inferior instrument. Its defects are: 1. The elasticity of the corrugated top of the vacuum chamber is affected by repeated changes in pressure. This will produce error in the scale readings.
Pagina 166 - B, and the line ae is drawn along the edge of the rule. The point e (the intersection of these two lines) will be in the line passing through the middle point and the point sought. Set the alidade upon the line be, direct b to the signal B by revolving the table, and the table will be in position.
Pagina 293 - The cistern (Fig. 12) is made up of a glass cylinder F, which allows the surface of the mercury q to be seen, and a top plate G. through the neck of which the...
Pagina 293 - G, t, j, and k, are of boxwood ; the other parts of brass or German silver. The screw O serves to adjust the mercury to the ivory point, and also, by raising the bag, so as to completely fill the cistern and tube with mercury, to put the instrument in condition for transportation.
Pagina 167 - D, so that the intersections from C and D upon A and B make sufficiently large angles for good determinations. Put the table approximately in position at D, by estimation or by compass, and draw the lines Aa and B6, intersecting at d; through d draw a line directed to C.
Pagina 144 - Observatory, so that when the mean azimuth of the line was corrected for this 15" error in latitude it agreed exactly with the stellar azimuth of the line, which might have been 10" or 15" in error. On the first day all the readings were taken without a reading glass, there being four circle readings to each result. On the second day a glass was used. " On the first day the maximum error was 4 minutes, the average error was 0.8 minute, and the 'probable error of a single observation
Pagina 293 - B by means of four long screws P and the ring R; on the ring R screws the cap S, which covers the lower parts of the cistern, and supports at the end the adjusting-screw 0.
Pagina 300 - If carried on horseback, it should be strapped over the shoulders of the rider, where it is not likely to be injured, unless the animal is subject to a sudden change of gait.
Pagina 300 - When about to be used it should be taken from its case, while screwed up, gently inverted and hung up, when it can be unscrewed. While it has its cistern uppermost the tube is full, is one solid mass of metal and glass, and not easily injured ; but when hung up, a sudden jolt might send a bubble of air into the vacuum at the upper end of the tube, and the instrument would be useless until repaired.''* 20 § 11.