--- title: "Methods of orienting plane table" subject: "Surveying I" chapter: 6 key: "semester_3/surveying_i:methods-of-orienting-plane-table" source: https://www.bctengineer.com/q/semester_3/surveying_i/methods-of-orienting-plane-table site: BCT Engineering --- # Methods of orienting plane table Surveying I · Chapter 6: Plane Table Survey - Asked in: 2076 Chaitra, 4 marks - Video: [Plane Table Surveying: ORIENTATION BY BACK SIGHT METHOD](https://www.youtube.com/watch?v=9lZEZ8RIafw) — Er Joga Singh Civil Engineer - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/surveying_i/methods-of-orienting-plane-table - Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-6 ## Question What are the methods of orienting a plane table? Describe the methods of plane table surveying with their salient features. ## Short answer Plane table orientation uses trough compass (quick, for small work) or back‑sighting (reliable, for traversing). The four surveying methods: radiation (distance and ray from one station), intersection (two‑ray fix from base line, for inaccessible points), traversing (table moved and oriented along a route), and resection (locating the table station from known plotted points). ## Answer #### Methods of orienting the plane table Orientation means placing the board at a new station so that all lines on the sheet are parallel to the corresponding ground lines. There are two methods: 1. **By trough compass (magnetic needle):** the trough compass is placed along the magnetic meridian line drawn on the sheet at the first station, and the board is turned until the needle floats at the zero marks. Quick but affected by local attraction, so it is used only for small work or for rough orientation. 2. **By back-sighting:** the alidade is placed along the line joining the present station to the previously plotted station, and the board is turned until the previous station is bisected. This is the more reliable method used in traversing and in intersection. #### Methods of plane table surveying The four methods are: 1. **Radiation** - rays are drawn from one station to the points to be plotted and distances are measured and scaled along them. 2. **Intersection** (triangulation) - a point is fixed by drawing rays to it from two stations at the ends of a plotted base line. 3. **Traversing** - the table is set up at successive stations of a traverse; each new station is plotted by radiation and the table is oriented by back-sighting. 4. **Resection** - the table station itself is located by drawing rays *back* from known plotted points to it (two-point and three-point problems). **Salient features** | Method | Salient features | |---|---| | Radiation | One station; rays and scaled distances; best for small, open areas | | Intersection | Base line only; points fixed by two intersecting rays; for inaccessible points | | Traversing | Table moved from station to station; for long narrow strips like roads and canals | | Resection | Table station fixed by rays back to known points; two-point and three-point problems | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What are the two methods of orienting a plane table? A. Trough compass and back-sighting B. Radiation and intersection C. Traversing and resection D. Levelling and centring Answer: A. Orientation is done by magnetic needle or by back-sighting. (Key point: Methods of orientation) 2. Why is the compass method used only for rough or small work? A. It is very slow B. It is affected by local attraction C. It needs a measured base line D. It requires a theodolite Answer: B. Local attraction makes it unreliable. (Key point: Compass limitation) 3. Which set lists the four methods of plane table surveying? A. Radiation, levelling, centring, orientation B. Chaining, booking, plotting, closing C. Radiation, intersection, traversing, resection D. Intersection, repetition, reiteration, traversing Answer: C. These are the four methods of plane tabling. (Key point: Four methods) 4. For what work is traversing best suited? A. Small open areas B. Inaccessible single points C. Fixing the table station from known points D. Long narrow strips like roads and canals Answer: D. The table moves from station to station along the strip. (Key point: Traversing use) ## Related in Surveying I - [Plane and geodetic surveying; principles](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aplane-geodetic-and-principles) — Surveying I, chapter 1, asked 7× - [Plane versus geodetic surveying](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aplane-vs-geodetic-surveying) — Surveying I, chapter 1, asked 5× - [Objectives of surveying; plane vs geodetic](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aobjectives-plane-geodetic) — Surveying I, chapter 1 - [Methods of plane table survey](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Amethods-of-plane-table-survey) — Surveying I, chapter 6, asked 6× - [Plane table principles; orientation by back sighting](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aorientation-back-sighting) — Surveying I, chapter 6, asked 4× - [Plane table principles; advantages, disadvantages](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aprinciples-adv-disadv-plane-table) — Surveying I, chapter 6, asked 2× ## Related in other subjects - [Kennedy's theory features and limitations](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Akennedy-theory-features-limitations) — Irrigation and Drainage Engineering, chapter 4 - [Short note: Total station features and uses](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atotal-station-features-uses) — Surveying II, chapter 9, asked 18× - [Total station features and data recording steps](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atotal-station-features-data-recording) — Surveying II, chapter 9 - [Total station, features, data recording points](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atotal-station-features-recording-points) — Surveying II, chapter 9