Survey accessories — identify the correct uses: box sextant, cross-staff, gradiometer, and line ranger in routine field practice.

Introduction / Context:
Efficient field surveying relies on simple yet specialized instruments that speed up routine tasks. Knowing which accessory to use for a specific operation prevents mistakes and improves productivity. This question checks recognition of the standard functions of four common tools: box sextant, cross-staff, gradiometer, and line ranger.

Given Data / Assumptions:

• Field tasks include setting right angles, measuring small angles, establishing gradients, and lining in intermediate points.
• Only the primary/common use of each device is considered.
• Instrumentation is assumed to be in standard condition.

Concept / Approach:

Box sextant: a compact optical instrument for measuring relatively small horizontal (and sometimes vertical) angles by sextant principle. Cross-staff: a simple device with perpendicular slots/vanes used to set out right angles to a chain line (for offsets). Gradiometer: used to set and check required gradients/slopes rapidly on site (e.g., drains). Line ranger: an optical device that helps position intermediate points directly on a straight survey line by visually aligning with end stations. All statements listed are correct uses, so the comprehensive answer is ‘‘All the above.’’

Step-by-Step Solution:

Verification / Alternative check:

Training manuals and practical surveying guides specify these exact functions for the respective tools, confirming correctness.

Why Other Options Are Wrong:

If a single statement were chosen, it would omit other equally true statements; the question explicitly groups multiple correct uses.

Common Pitfalls:

Confusing line rangers with ranging rods; using a cross-staff where higher angular precision (e.g., theodolite) is required.

Final Answer:

All the above