Precision traverse technique: When measuring included angles in a precision traverse using a vernier theodolite, which initial vernier setting practice is recommended to minimize systematic errors and achieve reliable mean angles?

Introduction / Context:
In a precision traverse, included angles are observed carefully to control closure error. Vernier or micrometer theodolites allow several good practices for setting the initial reading at the back station. The goal is to reduce instrumental and pointing biases by repetition, reversal, and averaging across different initial settings.

Given Data / Assumptions:

• A vernier theodolite (or micrometer theodolite) is used.
• Included angles are measured from a known back station direction to the forward station.
• Both-face observations and multiple repetitions may be taken.

Concept / Approach:
Systematic errors such as circle eccentricity and index error can be mitigated by varying the initial circle reading and by reading both verniers. Common practices include setting exactly 0°, an offset such as 5°, or a convenient near-zero value and then taking readings on both verniers for averaging. All achieve the same purpose: to diversify initial settings and distribute instrumental imperfections so that the mean angle is robust.

Step-by-Step Solution:

Verification / Alternative check:
Traverse adjustment (angular misclosure) and consistency between face-left and face-right means confirm that any of these starting practices produce equivalent precise results when combined with averaging and proper procedures.

Why Other Options Are Wrong:

• Options A, B, and C, taken alone, are each valid but incomplete recommendations. The most comprehensive answer is that all are acceptable.

Common Pitfalls:
Failing to read both verniers when available; not reversing the telescope; neglecting to re-point accurately after resetting the initial reading; assuming only one fixed initial reading eliminates all errors.

Final Answer:
All of the above practices are acceptable for precise work