What error does the gyrocompass error measure?

The gyrocompass error specifically measures the difference between true heading and gyrocompass heading. This discrepancy can arise due to several factors, such as the inherent imperfections in the gyrocompass system itself or disturbances from magnetic influences. The true heading is based on the Earth's rotation and a fixed reference point, while the gyrocompass provides a heading that is subject to drift and errors from its mechanical design.

Understanding this particular error is crucial for navigators, as it helps them adjust their course and maintain accuracy in navigation by ensuring that the heading data provided by the gyrocompass aligns more closely with true north. By measuring and correcting for gyrocompass error, mariners can enhance navigation reliability and safety.