---
title: "Field procedure of compass traversing"
subject: "Surveying I"
chapter: 4
key: "semester_3/surveying_i:compass-traverse-field-procedure"
source: https://www.bctengineer.com/q/semester_3/surveying_i/compass-traverse-field-procedure
site: BCT Engineering
---

# Field procedure of compass traversing

Surveying I · Chapter 4: The Compass

- Asked in: 2064 Jestha, 6 marks
- Video: [COMPASS SURVEYING](https://www.youtube.com/watch?v=x9ZPMxrlS3U) — CIVIL ENGINEERING FUNDA
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/surveying_i/compass-traverse-field-procedure
- Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-4

## Question

Describe the field procedure of compass traversing.

## Short answer

After selecting intervisible stations and fixing ranging rods, set up the compass over each station, level it, observe fore and back bearings, and measure line lengths with a tape. Check that FB – BB = 180° for each line; for a closed traverse also check the sum of interior angles equals (2n–4)×90°.

## Answer

A compass traverse is a series of connected lines whose lengths are measured with a chain or tape and whose bearings are measured with a compass. It may be closed (a loop) or open.

#### Reconnaissance and marking

1. Walk over the area and choose stations so that adjacent stations are intervisible, the lines are free of obstructions, and the stations are away from sources of local attraction (power lines, iron objects).
2. Mark the stations with pegs and fix a ranging rod over each. Draw a **reference sketch** of each station and an index sketch of the whole traverse.

#### Observations (at each station)

1. Set up the compass over the station with a plumb bob (or by dropping a pebble) and level it.
2. Sight the ranging rod at the preceding station (back station) and read the **back bearing** of the previous line; note it.
3. Sight the next (forward) station and read the **fore bearing**.
4. Measure the length of the line by chain or tape, with offsets and details if required.
5. Move to the next station and repeat. At the last station, close back to the starting station.

#### Booking

Enter the station names, the lengths, and the FB and BB in a field book. Check that $\text{FB} - \text{BB} = 180^\circ$ for each line.

#### Checks and closure

- If FB and BB differ by $180^\circ$, there is no local attraction; otherwise, correct the bearings for local attraction.
- For a closed traverse, check that the interior angles sum to $(2n - 4) \times 90^\circ$ and compute the closing error.
- Plot the traverse by the included-angle or coordinate method, and adjust the closing error by Bowditch's rule.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Stations in reconnaissance should be chosen so that:
   A. They are all on iron structures
   B. They are on one straight line
   C. Adjacent stations are intervisible and away from local attraction
   D. Only one station is visible
   Answer: C. Lines must be clear and free of magnetic influence. (Key point: Station selection)

2. At each station the surveyor reads:
   A. Only the FB
   B. Only the length
   C. Declination and dip
   D. BB of the previous line and FB of the next line
   Answer: D. Back sight gives BB, forward sight gives FB. (Key point: Observations)

3. In booking, the check for each line is:
   A. FB - BB = 180°
   B. FB = BB
   C. FB + BB = 90°
   D. FB - BB = 360°
   Answer: A. A difference other than 180° indicates local attraction. (Key point: Booking check)

4. For a closed traverse the interior angles should total:
   A. (n + 2) x 180°
   B. (2n - 4) x 90°
   C. n x 90°
   D. 360°
   Answer: B. This is the geometric angle sum; the closing error is also computed and Bowditch-adjusted. (Key point: Closed traverse check)

## Related in Surveying I

- [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×

## Related in other subjects

- [Field measurements in traversing, closed/open traverse](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-field-measurements-closed-open) — Surveying II, chapter 1
- [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
- [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