--- title: "Contouring methods, direct method field procedure" subject: "Surveying II" chapter: 4 key: "semester_4/surveying_ii:contouring-methods-direct-field-procedure" source: https://www.bctengineer.com/q/semester_4/surveying_ii/contouring-methods-direct-field-procedure site: BCT Engineering --- # Contouring methods, direct method field procedure Surveying II · Chapter 4: Contouring - Asked in: 2075 Bhadra, 6 marks - Video: [Direct Method of Contouring|| Auto level and Plane Table](https://www.youtube.com/watch?v=GKqhQJsi6U0) — Learn Surveying - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/surveying_ii/contouring-methods-direct-field-procedure - Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-4 ## Question What are the methods of contouring? Describe about field procedures of direct method of contouring. ## Short answer Contouring methods are direct (contours traced on ground, suitable for small areas) and indirect (spot levels interpolated). In the direct method, establish control and a benchmark, set up a level, find HI = RL_BM + BS, and required staff reading r = HI - contour RL. Move the staff until reading r is obtained, mark the point, then locate pegs from control by plane table or theodolite, joining equal RL points by smooth curves. ## Answer #### Methods of contouring There are two methods: 1. **Direct method:** the contours are traced on the ground and then located. It is suitable for small areas and large-scale maps. 2. **Indirect method:** spot levels are taken at grid points, along cross-sections or along radial lines, and the contours are interpolated. It is suitable for large areas. Its types are the method of squares, the method of cross-sections and the radial line method (tacheometry is also used). #### Field procedure of the direct method 1. Establish control (traverse stations) and a benchmark in the area. 2. Set up a level at a convenient point, take a back-sight on the BM and find the height of instrument: $HI = RL_{BM} + BS$. 3. For a contour of RL $h$, the required staff reading is $r = HI - h$. The staff man moves up or down the slope until the staff reading equals $r$; that point lies on the contour. Mark it with a peg. 4. Find several points on the same contour, then move to the next contour (the staff reading changes by the CI). 5. When the level is shifted, a new HI is found by sighting a fixed point (change point). 6. The pegs are then located from the control stations by **plane table, theodolite (tacheometer), chain or compass** and plotted on the sheet. The points of equal RL are joined by a smooth curve. On steep ground a clinometer or a hand level may be used with a ranging rod. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the main difference between direct and indirect contouring? A. Direct traces contours on the ground; indirect takes spot levels and interpolates contours B. Direct uses a theodolite; indirect uses a chain C. Direct is for large areas; indirect for small areas D. Direct needs no levelling Answer: A. In direct contouring contour points are found on the ground; in the indirect method only spot levels are taken and contours are interpolated. (Key point: Direct vs indirect) 2. In the direct method the height of instrument is found as: A. HI = RL_BM - BS B. HI = RL_BM + BS C. HI = RL_BM + FS D. HI = BS - FS Answer: B. Back-sight on the BM gives HI = RL_BM + BS. (Key point: Height of instrument) 3. The staff reading required for a contour of RL h is: A. HI + h B. h - HI C. HI - h D. BS + h Answer: C. A point on contour h reads r = HI - h; the staff man moves until the staff shows r. (Key point: Required staff reading) 4. When the level is shifted during direct contouring, the new HI is found by: A. Estimating it B. Sighting a fixed point (change point) C. Using the old HI D. Measuring with a tape Answer: B. A change point of known RL is sighted from the new position to get the new HI. (Key point: Shifting the level) 5. After the contour points are pegged they are: A. Located from control stations by plane table, theodolite, chain or compass and plotted B. Left unplotted until interpolation C. Joined directly on the ground D. Located by echo sounder Answer: A. Pegs are fixed in plan from the control stations and plotted; equal-RL points are joined by smooth curves. (Key point: Locating the pegs) ## Related in Surveying II - [Direct contouring method, uses of contour map](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Adirect-contouring-uses-contour-map) — Surveying II, chapter 4 - [Field procedure of aerial photogrammetry, relief displacement](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aaerial-photogrammetry-field-procedure-relief-displacement) — Surveying II, chapter 7, asked 2× - [Traverse field procedure between two known stations](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-field-procedure-between-known-stations) — Surveying II, chapter 1 - [Three-wire stadia field procedure for topo map](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Athree-wire-stadia-field-procedure) — Surveying II, chapter 2 - [Stadia principle and field procedure](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Astadia-principle-field-procedure-topo) — Surveying II, chapter 2 - [ODM principle, tacheometric field procedure](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aodm-principle-field-procedure-theodolite) — Surveying II, chapter 2 ## Related in other subjects - [Field procedure of chain surveying](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Afield-procedure-chain-survey) — Surveying I, chapter 3, asked 4× - [Field procedure of compass traversing](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Acompass-traverse-field-procedure) — Surveying I, chapter 4 - [Frequency response design procedure](https://www.bctengineer.com/question.md?key=semester_6%2Fdigital_control_system%3Afrequency-response-design-procedure) — Digital Control System, chapter 4 - [Horizontal angles from field notes, triangle ABC](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Atheodolite-field-notes-abc-64-jestha) — Surveying I, chapter 7