--- title: "Field measurements in traversing, closed/open traverse" subject: "Surveying II" chapter: 1 key: "semester_4/surveying_ii:traverse-field-measurements-closed-open" source: https://www.bctengineer.com/q/semester_4/surveying_ii/traverse-field-measurements-closed-open site: BCT Engineering --- # Field measurements in traversing, closed/open traverse Surveying II · Chapter 1: Traversing - Asked in: 2070 Bhadra, 4+4 marks - Video: [Traverse Surveying Tutorial](https://www.youtube.com/watch?v=pCYs9rQMACQ) — Amani Adha - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/surveying_ii/traverse-field-measurements-closed-open - Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-1 ## Question Write the field measurements required in theodolite traversing and explain closed and open traverses. ## Short answer Field measurements: horizontal angles (both faces), line lengths (tape/EDM with corrections), starting bearing, vertical angles for slope reduction, and offset details. Closed traverse: returns to start or connects known points, offering mathematical checks. Open traverse: ends at unknown point, no closure check; used in route surveys and checked by repeat measurement. ## Answer #### Field measurements in theodolite traversing 1. **Horizontal angles** at each station: included angles, deflection angles or direct (azimuth) angles, observed on both faces and repeated or in sets to reduce instrumental errors. 2. **Lengths of the traverse lines:** measured with a steel tape (twice, forward and back, with temperature, tension, slope and sag corrections) or with an EDM/total station. 3. **Bearing of the starting line:** magnetic bearing by a compass or true bearing by astronomical or GPS observation; in a link traverse, the bearings of the reference lines at both ends. 4. **Vertical angles or levels** of the stations, where the heights are required or the lengths are inclined (for slope reduction). 5. **Details and offsets** from the traverse lines (building corners, roads, streams), with a sketch and the station numbers. 6. **Station description and referencing** (ties to permanent objects), the height of the instrument and signals, and all booking in the field book. #### Closed and open traverses - **Closed traverse:** a traverse that ends where it began (a *closed loop*) or that starts and ends on stations of known position (a *closed link/connecting traverse*). It gives a mathematical check on the field work. - **Open traverse:** a traverse that starts at a known station and ends at a point of unknown position, so there is no closing check. It is used for roads, canals, pipelines and similar route surveys, and the angles and lengths must be checked by repeat measurement. ```text Closed loop Closed link Open traverse B----C K1--1--2--3--K2 A---B / \ (known) (known) \ A D C---D \ / \ F----E E (end, (returns to A) (ends on known K2) unknown) ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How are horizontal angles observed in theodolite traversing to reduce instrumental errors? A. On both faces, repeated or in sets, taking the mean B. On face left only C. Once with the telescope plunged D. With a compass Answer: A. Observing on both faces and in sets cancels instrument errors. (Key point: Angle observation) 2. How are traverse line lengths measured with a steel tape? A. Once, uncorrected B. Twice, forward and back, with temperature, tension, slope and sag corrections C. By pacing D. By stadia only Answer: B. Repeated measurement and the usual tape corrections give a reliable length; EDM may be used instead. (Key point: Length measurement) 3. Which describes a closed traverse? A. It ends at a point of unknown position B. A closed loop, or a link traverse between known stations, giving a mathematical check C. A traverse with no angle measurements D. Any traverse of more than four sides Answer: B. Closed traverses either return to the start or end on a known station, so the work can be checked. (Key point: Closed traverse) 4. What is the main drawback of an open traverse? A. It cannot be plotted B. There is no closing check, so angles and lengths must be checked by repeat measurement C. It needs a GPS D. It must have an even number of sides Answer: B. An open traverse ends at an unknown point, so errors cannot be detected by closure; it is used for roads, canals and pipelines. (Key point: Open traverse) ## Related in Surveying II - [Field measurements in traversing, Bowditch rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-field-measurements-bowditch-rule) — Surveying II, chapter 1 - [Closed/open traverse, transit rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-open-traverse-transit-rule) — Surveying II, chapter 1, asked 2× - [Closed/open traverse, Bowditch's rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-open-traverse-bowditch-rule) — Surveying II, chapter 1, asked 2× - [Closed/open traverse, consecutive, independent coordinates](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-open-traverse-consecutive-independent) — Surveying II, chapter 1 - [Principles and planning of theodolite traverse](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atheodolite-traverse-principles-planning) — Surveying II, chapter 1 - [Steps of closed traverse computation](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-traverse-computation-steps) — Surveying II, chapter 1 ## Related in other subjects - [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 - [Theodolite traverse ABCDA with missing VCR (68°30′10″)](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Atheodolite-traverse-abcda-hcr-vcr-68-30-10) — Surveying I, chapter 7 - [Theodolite traverse ABCDA, booking format with VCR](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Atraverse-abcda-booking-format-vcr-120-14-20) — Surveying I, chapter 7 - [Open traverse ABCDEFG, deflection angles](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aopen-traverse-deflection-angles-40-45) — Surveying I, chapter 4, asked 2×