A bearing measured clockwise from true north, used for chart plotting and unaffected by magnetic variation or compass deviation.
In practice
On watch, the OOW records bearings as true in the bridge log and uses them to plot position lines on the chart or ECDIS. When taking visual bearings with the pelorus and correcting via the gyrocompass output, the resulting true bearing can be applied directly. In celestial navigation, the calculated azimuth of a heavenly body is a true bearing, used to compare with the observed compass bearing to determine compass error. Absolute accuracy in true bearings is essential: an error of even a few degrees in a position line can shift the plotted position by a significant margin in restricted waters.
Regulatory detail & full definition
A true bearing is the direction from the observer to an object measured clockwise from true geographic north, expressed in degrees from 000° to 359°. It is the fundamental reference used for all chart work because navigational charts are oriented to true north and all charted features—coastlines, lights, buoys, and hazards—are plotted in relation to true north. Bowditch (American Practical Navigator) explains that a true bearing obtained from a gyrocompass requires no further correction, whereas a magnetic or compass bearing must first be corrected for deviation (to give magnetic) then for variation (to give true) before it can be plotted on the chart.
On watch, the OOW records bearings as true in the bridge log and uses them to plot position lines on the chart or ECDIS. When taking visual bearings with the pelorus and correcting via the gyrocompass output, the resulting true bearing can be applied directly. In celestial navigation, the calculated azimuth of a heavenly body is a true bearing, used to compare with the observed compass bearing to determine compass error. Absolute accuracy in true bearings is essential: an error of even a few degrees in a position line can shift the plotted position by a significant margin in restricted waters.