--- title: "Profile and cross-section levelling" subject: "Surveying I" chapter: 5 key: "semester_3/surveying_i:profile-and-cross-section-leveling" source: https://www.bctengineer.com/q/semester_3/surveying_i/profile-and-cross-section-leveling site: BCT Engineering --- # Profile and cross-section levelling Surveying I · Chapter 5: Leveling - Asked in: 2081 Bhadra, 4 marks; 2079 Bhadra, 4 marks; 2076 Chaitra, 2+3 marks; 2073 Shrawan, 4 marks; 2066 Jestha, 7 marks; 2066 Bhadra, 7 marks; 2065 Shrawan, 7 marks; 2062 Baisakh, 8 marks; 2061 Baisakh, 6 marks; 2059 Chaitra, 6 marks (asked 10 times) - Video: [Profile and cross sectional Levelling : Surveying Practical](https://www.youtube.com/watch?v=irNlaNP63nA) — The Classroom - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/surveying_i/profile-and-cross-section-leveling - Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-5 ## Question Explain profile (longitudinal section) levelling and cross-section levelling with suitable sketches, and their uses in civil engineering. ## Short answer Profile levelling takes levels along a centre line to plot longitudinal section; cross-section levelling takes perpendicular levels at chainages. Uses: fixing gradients, cut/fill depths, computing earthwork volumes for roads, railways, canals. ## Answer **Profile levelling (longitudinal sectioning)** is levelling along a fixed line, such as the centre line of a road, canal, railway, or pipeline, to find the reduced levels of points along it at regular intervals (usually 10 m, 20 m, 30 m) and at every change of slope. The levels are plotted against chainage to get the longitudinal section (profile) of the ground. **Cross-section levelling** is levelling along lines at right angles to the centre line at each chainage, to find the ground levels on both sides. Cross-sections show the ground profile across the alignment and give the width to be cleared and the volume of earthwork. #### Field procedure 1. Peg the centre line at the required intervals and mark the chainages. 2. Set the level at a convenient point; take a BS on the BM and then IS on every peg along the centre line (the staff is held on the ground at each chainage and at breaks of slope); take FS on a change point when the instrument must be shifted. 3. For cross-sections, at each chainage set a line at right angles (with a cross-staff or prismatic square) and take staff readings at fixed offsets (e.g. 5 m, 10 m, 15 m) on the left and right, as IS. 4. Close the survey on another BM (or the first BM) and apply the arithmetic check and misclosure adjustment. ```text Longitudinal section Cross-section at ch. 120 (RL vs chainage) left CL right ______ \ | / ___/ \___ ground \____|____/ -------------------- datum 15 5 0 5 15 m 0 30 60 90 120 ``` #### Uses in civil engineering - To fix the formation level, gradient and depth of cutting/filling of a road, railway or canal. - To compute earthwork quantities from the cross-sections (area and volume). - To design the longitudinal gradient of sewers, water pipes and drains. - To select the best alignment of roads and canals. - To find the capacity of reservoirs and to plan bridge sites. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is profile (longitudinal section) levelling? A. Levelling along lines at right angles to the centre line B. Levelling along the centre line at regular intervals and at changes of slope, then plotting RL against chainage C. Levelling between two points on opposite river banks D. Levelling to find the instrument's collimation error Answer: B. Profile levelling gives the RLs of points along the alignment, plotted as a longitudinal section. (Key point: Profile levelling) 2. How are cross-sections taken? A. Along the centre line with 10 m intervals B. At right angles to the centre line at each chainage, with readings at fixed offsets on both sides C. Only at change points D. Using barometers on both sides Answer: B. A line at right angles is set out at each chainage, and staff readings are taken left and right at fixed offsets as intermediate sights. (Key point: Cross-sections) 3. Which sight types are used in the field work? A. IS on every peg along the line, with FS and BS on change points when the instrument is shifted B. FS on every peg C. BS on every peg D. IS only; no BS or FS Answer: A. BS on the BM, IS on pegs, FS and new BS at change points, and the survey is closed on a BM. (Key point: Field procedure) 4. What is a main use of cross-sections? A. Finding the collimation error B. Calculating earthwork area and volume, and the width to be cleared C. Measuring horizontal angles D. Finding magnetic declination Answer: B. Cross-sections give ground profiles across the alignment from which earthwork quantities and widths are computed. (Key point: Uses) ## Related in Surveying I - [Profile levelling; balancing of sight](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aprofile-leveling-balancing-of-sight) — Surveying I, chapter 5 - [Level book and longitudinal section, RL 525.50](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Alevel-book-chainage-200m-rl-525-50) — Surveying I, chapter 5 - [Level book: profile levelling readings](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aprofile-leveling-readings-3rd-7th-9th) — Surveying I, chapter 5 - [Reciprocal levelling and its significance](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Areciprocal-leveling-significance) — Surveying I, chapter 5, asked 3× ## Related in other subjects - [Longitudinal section of a head regulator](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Ahead-regulator-longitudinal-section) — Irrigation and Drainage Engineering, chapter 7 - [Types of cross drainage works with sketches](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acd-works-types-definition-sketches) — Irrigation and Drainage Engineering, chapter 8, asked 9× - [Velocity profile in channel cross-sections](https://www.bctengineer.com/question.md?key=semester_4%2Fhydraulics%3Avelocity-profile-channel-shapes) — Hydraulics, chapter 5 - [Scope and importance of geology in civil engineering](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ascope-and-importance-of-geology) — Engineering Geology I, chapter 1, asked 24×