Astronomical north, bearing, and azimuth – pick the correct combined statement Which of the following statements about astronomical directions and bearings is correct?

Introduction / Context:
In astronomical and geodetic surveying, the local horizon system uses true (astronomical) north as a reference. Bearings and azimuths derived from the celestial sphere ensure consistent orientation over large distances and time.

Given Data / Assumptions:

• True north is defined by the direction of the celestial pole on the horizon.
• Bearings/azimuths are measured clockwise from true north in practical surveying contexts.

Concept / Approach:
The astronomical north direction points toward the projection of Earth’s axis (celestial pole). The astronomical bearing (often termed azimuth) of a line is the angle at the observer between true north and the line, measured in the horizontal plane.

Step-by-Step Solution:
Confirm definition of astronomical north → direction toward the celestial pole on the horizon.Define astronomical bearing → horizontal angle from true north to the line.Recognize common terminology → azimuth is the same concept in this context.

Verification / Alternative check:
Standard surveying texts equate astronomical bearing with azimuth referenced to true north (as opposed to magnetic bearings referenced to magnetic north).

Why Other Options Are Wrong:
Since (a), (b), and (c) are all correct, “None of these” is incorrect; the comprehensive answer is “All of the above”.

Common Pitfalls:
Confusing magnetic north with astronomical (true) north; mixing quadrant bearings with whole-circle azimuths.

Final Answer:
All of the above