. Engineering and Contracting . at for afixed A. the deflections to points of equal division on a curveremain tor any length of the curve. This makes themethod perfectly general. The order of procedure in laying out a curve is as follows:(1) set up the instrument at the , backsight on the firsttangent with verner reading 0°, transit the telescope, un-clamp the vernier and fix the line of sight on the second tan-gent, the vernier giving the deflection angle A°: 2) decidevhat length of curve to use (determined usually either by thedesired external distance E or the tangent length
. Engineering and Contracting . at for afixed A. the deflections to points of equal division on a curveremain tor any length of the curve. This makes themethod perfectly general. The order of procedure in laying out a curve is as follows:(1) set up the instrument at the , backsight on the firsttangent with verner reading 0°, transit the telescope, un-clamp the vernier and fix the line of sight on the second tan-gent, the vernier giving the deflection angle A°: 2) decidevhat length of curve to use (determined usually either by thedesired external distance E or the tangent length (T: (3)compute T and E, using either the well known tables of tan-gents and externals for a 1° curve, or preferably the tangentsand externals for a 100 ft. curve Table (II); (4) lay off thetangent length locating the end of the curve (the P. T.); (5)divide the length of curve by 10 and locate each of the tenpoints, or every other one. or every third one, dependingupon how many are needed to properly define the curve, by. â¢Copyright, 1920, by T, F. Hickerson. Fig. at the P,T,, and getting the intersection of the endof the chord with the line of sight from the P,I,. according todeflections read directly from the tables (Table 1). The middle point, or the 5th point of the curve, cannot belocated very precisely by intersections, since the end of thechord would be moved in an arc tangent to the line of point can be located exactly by measuring the externaldistance E from the , and this serves as a check. If onlythe 2nd, 4th, 6th, 8th, and 10th points are located, then it isnot necessary to know E. The beginning of the curve (the ) is located as the 10thpoint by a deflection which is always 180°. The station num- (158) Engineering and Contracting for June 2, 1920. 619 C-r^-i-^-£^/920 TAWji I- Dj?mc?ioan ?r,oi: ?hj to lOin? or .; uu. Divi-roa ^^ r.,-cKcrs<i- ALO»0 CIBOOlAR OUBTE. 1- sMi . SSS . 463 . *-3S .
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