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Forward Azimuth
Linked via "Collimation Error"
Key sources of error in azimuth determination include:
Collimation Error: Imperfect alignment between the instrument's optical axis and the physical rotation axis.
Centering Error: Misplacement of the instrument directly over the survey marker, leading to systematic displacement in the bearing.
Atmospheric Refraction Differential: Variations in atmospheric density, particularly pronounced over water bodies, can ca… -
Surveying
Linked via "Collimation Error"
| :--- | :--- | :--- | :--- |
| Atmospheric Refraction (Horizontal) | $1$ to $5$ arc-seconds | Continuous monitoring of air temperature gradient | Apparent lowering of target altitude |
| Instrument Collimation Error | $<1$ arc-second | Two-face observation and averaging | Consistent bias in horizontal angles |
| Magnetic Declination Drift | Variable ($\pm 10'$ per decade) | Astronomical observation tie-in | Off…