. Elements of precise surveying and geodesy. star, and themean of these times is that to be usedto find the hour-angle /. The processof finding / by the help of the nauticalalmanac is shown in the lower part ofthe table. Then from the formula tanZ is found to benegative and hence the star was west of the meridian;accordingly ^ is — o° 59 o6\3, and finally the geodeticazimuth of the line AB is 175° 57 , the probable errorof which may be estimated at 10 or 15. Making a numberof observations on different parts of the circle and takingtheir mean, a fair determination of azimuth may be obtained
. Elements of precise surveying and geodesy. star, and themean of these times is that to be usedto find the hour-angle /. The processof finding / by the help of the nauticalalmanac is shown in the lower part ofthe table. Then from the formula tanZ is found to benegative and hence the star was west of the meridian;accordingly ^ is — o° 59 o6\3, and finally the geodeticazimuth of the line AB is 175° 57 , the probable errorof which may be estimated at 10 or 15. Making a numberof observations on different parts of the circle and takingtheir mean, a fair determination of azimuth may be obtainedby one nights work. To secure the elimination of the instrumental errors of thetransit more completely, one half of the pointings on the starmay be made by looking at its reflection in a dish of mercuryplaced near the objective end of the telescope. When ageodetic theodolite is used corrections for the error of levelin the telescope standards are to be applied, unless this beeliminated by taking half the observations in a mercury hori-. 44. AZIMUTH BY POLARIS AT ANY HOUR-ANGLE. 123 zon. If a sidereal chronometer is at hand the time shouldbe noted by it, as thus the reduction of local mean solar timeto sidereal time is avoided. Azimuth by Polaris, April 29, 1897. Watch Time Tel. Readings on Mark. Readings on Star. Data. £> 25° 11 20 (p — 40° 36 24 R 25 II 20 A = 75° 22 50 8^ 16™ 30 R 30° 14 30 5 =. 88° 45 8 18 30 D 30 13 05 or = i 20 19°.2 8 20 30 D 30 II 50 8 22 30 R 30 10 40 Watch 93^-3 faster R 25 II 00 than Easternstandard time. D 25 11 10 J. Doe, observer. 8 ig 30 25° 11 I25. 30° 12 — 01 33-3 = — Watch error. 30° 12 Bh 17 — 01 56^.731 -3 =: Eastern standard Longitude correction. = Local mean solar time. = Reduction to sidereal interval. L 25 II 12 .5 iH = 5 01 iS .7 8 16+ 01 25-421 .7 Z= —0 59 06 .3 AN= 4 02 12 .4 2 30 48 .5 = Sidereal time Greenwichmean noon. Azimuth 180 ^i9=i75°5747-6 + 00 49 -4 = Longitude correcti
Size: 1080px × 2315px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjec, booksubjectsurveying
