--- title: "Closing error; plotting methods in compass traverse" subject: "Surveying I" chapter: 4 key: "semester_3/surveying_i:closing-error-plotting-methods" source: https://www.bctengineer.com/q/semester_3/surveying_i/closing-error-plotting-methods site: BCT Engineering --- # Closing error; plotting methods in compass traverse Surveying I · Chapter 4: The Compass - Asked in: 2075 Asoj, 4 marks - Video: [closed traversesurvey by Prismatic Compass.traverse a scale of 1: 3000 Removeclosing error if any.](https://www.youtube.com/watch?v=64E5k_FNVYg) — BHU Study - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/surveying_i/closing-error-plotting-methods - Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-4 ## Question Define closing error. Describe the various plotting methods in compass traverse. ## Short answer Closing error is the gap between the plotted end of a closed traverse and the starting point. Plotting methods include the included-angle method, the bearing (protractor) method, the tangent method (offset along meridian), and the coordinate method using latitudes and departures, which is the most accurate and allows Bowditch adjustment before plotting. ## Answer **Closing error:** when a closed traverse is plotted, the last point often falls at A′ instead of at the starting point A; the distance A′A is the closing error. The ratio (closing error / perimeter) shows the accuracy of the survey. #### Methods of plotting a compass traverse **1. Included (interior) angle method** - Calculate the interior angles from the FB and BB, plot the first line to scale, and at each station set out the angle with a protractor to plot the next line. Angular errors accumulate from station to station, but the sum of the angles can be checked first. Suitable for a closed traverse. **2. Bearing (protractor) method** - Draw a meridian line through each station and plot each line directly at its observed bearing with a protractor (circular or paper protractor), laying off the lengths to scale. It is simple and quick, and errors carry from one line to the next less than in the angle method, but the accuracy is limited by the protractor. **3. Tangent method** - A convenient length is laid off along the meridian (or along the previous line) from the station, and at its end a perpendicular offset equal to that length × tan(bearing or angle) is set off to scale. The line joining the station to this point gives the direction of the survey line. It is more accurate than using a protractor. **4. Co-ordinate (latitude and departure) method** - Compute the latitude $L\cos\theta$ and departure $L\sin\theta$ of every line, find the co-ordinates of each station, and plot the stations on a grid. It is the most accurate method, and the closing error can be adjusted by Bowditch's rule before plotting. After plotting, the closing error A′A is adjusted by Bowditch's rule. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Closing error in a plotted closed traverse is: A. The distance A'A between the plotted end point and the start B. The sum of angles C. The perimeter D. The scale error Answer: A. The last point falls at A' instead of A. (Key point: Closing error) 2. The most accurate method of plotting a compass traverse is: A. Protractor method B. Co-ordinate (latitude and departure) method C. Tangent method D. Included angle method Answer: B. Co-ordinates are computed and plotted on a grid. (Key point: Most accurate method) 3. Latitude and departure of a line are: A. L sin θ and L cos θ B. L tan θ and L C. L cos θ and L sin θ D. L/cos θ and L/sin θ Answer: C. Latitude = L cos θ (N-S), departure = L sin θ (E-W). (Key point: Latitude and departure) 4. Included angle method requires: A. Drawing a meridian at each station B. Using tangent offsets C. Computing coordinates only D. Plotting the first line then setting out the interior angle at each station Answer: D. Angles are set with a protractor to plot successive lines. (Key point: Included angle method) ## Related in Surveying I - [Factors of closing error; graphical adjustment](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aclosing-error-factors-graphical) — Surveying I, chapter 4 - [Closing error and graphical adjustment](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aclosing-error-graphical-adjustment) — Surveying I, chapter 4, asked 13× - [Local attraction: AB 69°30′ compass traverse](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Alocal-attraction-ab-69-30-reordered) — Surveying I, chapter 4 - [Closing error in a level circuit](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aclosing-error-level-circuit) — Surveying I, chapter 5 - [Two peg: closing error and precision of level](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Atwo-peg-cd-50m-e-mid-f-5m) — Surveying I, chapter 5 - [Plotting theodolite traverse; repetition errors](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aplotting-theodolite-traverse-repetition-errors) — Surveying I, chapter 7 ## Related in other subjects - [Plotting coordinated traverse on grid paper](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-plotting-grid-paper) — Surveying II, chapter 1, asked 2× - [Omitted measurement cases, traverse plotting](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aomitted-measurement-cases-plotting) — Surveying II, chapter 1 - [Closed loop/link traverse, grid plotting](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-loop-link-traverse-plotting-grid) — Surveying II, chapter 1 - [Consecutive, independent coordinates, plotting](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aconsecutive-independent-coordinates-plotting) — Surveying II, chapter 1