. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . introduce a substation at • anypoint, its deflection from the PC may bereadily interpolated. The stations actuallyset from the PC are located as When the transit is set on anyforward station, backsight to any previousstation with the plates set at the deflectionangb for the station sighted at. Plungeths tslsscope and sight at any forwardstation with tho deflection angb originallycomputed for that station.
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . introduce a substation at • anypoint, its deflection from the PC may bereadily interpolated. The stations actuallyset from the PC are located as When the transit is set on anyforward station, backsight to any previousstation with the plates set at the deflectionangb for the station sighted at. Plungeths tslsscope and sight at any forwardstation with tho deflection angb originallycomputed for that station. When theplates read the deflection angle for thestation occupied, the telescope is sightingalong the tangent at that station—whichis the method of getting the forward tan-gent when occupying the PT. Even thoughthe station occupied is an unexpected sub-station, when the instrument is properlyoriented at that station, the angle readingfor any station, forward or back, is that originally computedfor it from the PC. In difficult work, where there are ob-structions, a valuable check on the accuracy may be found bysighting backward at any visible station and noting whether. Fig. 16. §66. ALINBMENf. 65 its deflection agrees with that origirially computed. As anumerical illustration, assume a 4° eufVe, with 28° curvature,I with stations 0, 2, 4, atid 7 occupied. Aftef getting stations1 and 2, set tip the transit at sta. 2 and backsight to sta. 0Iwith the deflection for sta. 0, which is 0^. The reading on is 2°; when the reading is 4^ the telescope is tangent tothe curve, and when sighting at 3 and 4 the defections will be6^ and 8°. Occupy 4; sight to 2 with a reading ot 4^. Whenthe reading is 8*^ the telescope is tangent to the cUfve and, byplunging the telescope, 5, 6, and 7 may be located with theoriginally computed deflections of 10°, 12°, and 14°. When oc-cupying 7 a backsight may be taken to any visible statioti withthe plates reading the deflection for that sta
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
