Hydrographic instruments: The “station pointer” is a specialized plotting device most commonly used in which branch of surveying?

Introduction / Context:
Hydrographic surveys often fix a boat’s position at sea by resection from three known shore marks. A quick and reliable plotting tool is needed to turn angles and intersect arcs on paper charts.

Given Data / Assumptions:

• Three-point resection problem on a nautical chart.
• Shore signals or prominent objects with known charted positions.
• Measured angles between the three objects on board.

Concept / Approach:
The station pointer consists of a central arm and two adjustable outer arms that can be set to the measured angles. By placing the centre near the estimated position and adjusting to touch the three charted points simultaneously, the boat’s fix is obtained quickly. It is thus a standard instrument in hydrography for coastal and harbor surveys.

Step-by-Step Solution:
Measure the two included angles between three selected shore points.Set the station pointer to those angles (one on each outer arm).Slide/rotate until the three edges pass through the three charted points; the centre gives the vessel’s position.

Verification / Alternative check:
Classical hydrographic manuals describe station pointers as standard for three-point fixes; electronic positioning has reduced but not eliminated their instructional use.

Why Other Options Are Wrong:
Triangulation/Astronomical/Photogrammetric/Mining surveying use other primary instruments; the station pointer is characteristic of hydrography.

Common Pitfalls:
Poor selection of shore points with bad geometry (nearly collinear) leads to weak fixes; choose strong triangles with good intersection angles.

Final Answer:
Hydrographical surveying.