--- title: "Setting out right hand side composite curve" subject: "Surveying II" chapter: 6 key: "semester_4/surveying_ii:right-hand-composite-curve-setting-out" source: https://www.bctengineer.com/q/semester_4/surveying_ii/right-hand-composite-curve-setting-out site: BCT Engineering --- # Setting out right hand side composite curve Surveying II · Chapter 6: Curves - Asked in: 2065 Kartik (old course), 6 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/surveying_ii/right-hand-composite-curve-setting-out - Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-6 ## Question Describe about the setting out techniques of right hand side composite curve. ## Short answer Set out with theodolite and tape by deflection angles. TS and ST are located by measuring Ts from IP on both tangents. First transition from TS uses clockwise tangential angles; circular arc from SC uses clockwise deflection angles; second transition from ST uses anticlockwise angles. Check joins at SC and CS. ## Answer A **composite curve** has a circular arc between two transition (spiral) curves. A right-hand curve turns to the right of the direction of travel, so the deflection angles are measured **clockwise**. It is set out with a theodolite and tape by the deflection angle method. ```text V (IP) / \ / \ TS o/ \o ST \ SC CS / '--___--' ``` #### Preliminary computations 1. Length of spiral $L_s = v^3/(CR)$, shift $s = L_s^2/(24R)$, spiral angle $\theta_s = L_s/(2R)$. 2. Tangent length $T_s = (R+s)\tan(\Delta/2) + L_s/2$; $L_c = R(\Delta - 2\theta_s)$. 3. Chainages: TS = IP − $T_s$, SC = TS + $L_s$, CS = SC + $L_c$, ST = CS + $L_s$. 4. Deflection angles of the transition: $\alpha = 573\,l^2/(RL_s)$ minutes; of the circular arc: $\delta = 1718.87\,c/R$ minutes. #### Field procedure 1. **Locate TS and ST** by measuring $T_s$ from the IP along both tangents. 2. **First transition (instrument at TS):** set zero and sight the IP. Turn the telescope clockwise by $\alpha_1$, measure $l_1$ (sub-chord) from TS to fix point 1. Then set $\alpha_2$, swing the tape from point 1 and fix point 2, and so on to SC. The last angle is $\alpha_s = \theta_s/3$. 3. **Circular arc (instrument at SC):** sight TS with the plates set at $360^\circ - \tfrac{2}{3}\theta_s$, plunge the telescope and turn clockwise until the circle reads $0^\circ00'00''$; this line is the tangent at SC. Set clockwise deflection angles $\delta_1,\ \delta_1+\delta_2,\dots$ and fix the arc points with the chords. The last angle should be $(\Delta-2\theta_s)/2$ at CS. 4. **Second transition (instrument at ST):** set zero and sight the IP. Because this transition is set from the far end, the points are located by angles measured **anticlockwise** (reading $360^\circ - \alpha$ for a right-hand curve), with $l$ measured from ST back to CS. 5. **Check:** the arc and the two transitions must join exactly at SC and CS; any small misclosure is distributed over the last few pegs. If the full curve is not visible from the SC (obstruction), the instrument is shifted to an intermediate station and re-oriented by backsighting. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is a composite curve? A. A circular arc with a transition (spiral) curve at each end B. Two circular arcs of different radii joined together C. A parabola joined to a straight D. A circular arc followed by a reverse circular arc Answer: A. A composite curve has a circular arc between two transition curves, which gives gradual change of curvature. (Key point: Composite curve definition) 2. How are the chainages along a composite curve obtained? A. TS = IP + Ts, SC = TS - Ls, CS = SC - Lc, ST = CS - Ls B. TS = IP - Ts, SC = TS + Ls, CS = SC + Lc, ST = CS + Ls C. TS = IP - Ls, SC = TS + Lc, CS = SC + Ls, ST = CS + Lc D. TS = IP - Lc, SC = TS + Ls, CS = SC + Ls, ST = CS + Lc Answer: B. TS is found by subtracting the total tangent Ts from the IP, then each section length (spiral, arc, spiral) is added in order. (Key point: Chainages of key points) 3. For the circular arc, the instrument at SC is first oriented by sighting TS with the plates at 360° - (2/3)θs, then plunging and turning until the circle reads zero. What does this zero line represent? A. The line to the IP B. The long chord of the arc C. The tangent to the circular arc at SC D. The radius at SC Answer: C. The angle between the TS line and the tangent at SC is (2/3)θs, so the correction gives the common tangent at SC from which arc deflection angles are measured. (Key point: Setting the circular arc from SC) 4. For a right-hand curve set from TS, in which direction are the deflection angles turned, and how is the second transition from ST set? A. Anticlockwise at both TS and ST B. Anticlockwise at TS; clockwise at ST C. Clockwise at both TS and ST D. Clockwise at TS; anticlockwise at ST (reading 360° - α) Answer: D. For a right-hand curve angles from TS are clockwise, but the second transition is set from the far end, so angles are anticlockwise, read as 360° - α. (Key point: Direction of angles) 5. What is the check at the end of setting out a composite curve? A. The arc and transitions join exactly at SC and CS, the last arc angle being (Δ - 2θs)/2 B. The last arc angle is Δ at CS C. Sum of all chords equals the long chord D. Cumulative angle at ST equals 90° Answer: A. The curve should close at SC and CS, with final arc deflection (Δ - 2θs)/2; small misclosures are distributed over the last pegs. (Key point: Final check) ## Related in Surveying II - [Short note: Setting out vertical curve](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Avertical-curve-setting-out-note) — Surveying II, chapter 6 - [Setting out simple curve by Rankine's method](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Asimple-curve-rankine-method-sketch) — Surveying II, chapter 6 - [Composite curve design by Rankine's method](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acomposite-curve-rankine-design-2079j) — Surveying II, chapter 6, asked 2× - [Composite curve design, IP 1150 m, Rankine](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acomposite-curve-rankine-ip-1150) — Surveying II, chapter 6, asked 2× - [Short note: Rankine's method of curve setting](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Arankine-method-circular-curve) — Surveying II, chapter 6 - [Composite curve by deflection angle method](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Acomposite-curve-deflection-angle-method) — Surveying II, chapter 6, asked 5× ## Related in other subjects - [Fleming's right and left hand rules](https://www.bctengineer.com/question.md?key=semester_4%2Felectrical_machine%3Afleming-hand-rules) — Electrical Machine, chapter 1 - [Setting out of a building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asetting-out-building) — Building Technology, chapter 2 - [Composite curve with 48 degree deflection](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-72m-composite-60) — Transportation Engineering I, chapter 3 - [Composite curve, 65 kmph, centrifugal ratio 1/5](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-71bh-composite-65) — Transportation Engineering I, chapter 3