Short Sights & Centering – Techniques to Reduce Centering Error for Very Short Traverse Legs When working with very short traverse legs where centering error can dominate, which practices are commonly adopted to reduce the centering and pointing errors?

Introduction / Context:
On very short legs, the angular miscentering can create disproportionately large errors in computed bearings and coordinates. Practical field techniques aim to reduce the centering and pointing components so that instrument precision is actually realized. This question reviews several accepted practices.

Given Data / Assumptions:

• Traverse legs are short enough that a few millimetres of centering error matter.
• Standard theodolite with optical plummet is available.
• Simple targets (e.g., chain pins) may be used for very short sights.

Concept / Approach:

Mitigation strategies include: ensuring precise instrument centering with an optical plummet; using fixed targets on tripods so the instrument can be re-set exactly over the same point; employing chain pins as close-range sighting objects to reduce pointing uncertainty for very short observations. Collectively, these practices minimize lateral target definition errors and instrument centering offsets.

Step-by-Step Solution:

Verification / Alternative check:

Survey practice guides endorse optical centering and stable targets to control short-sight errors; numerous field crews adopt chain pins for convenience on very short legs.

Why Other Options Are Wrong:

All listed practices are valid in the stated context; therefore “All of the above” is correct and “None” is incorrect.

Common Pitfalls:

Ignoring centering on short legs; using handheld targets that move; failing to re-check centering after tightening screws.

Final Answer:

All of the above