Question 1811Navigation General

The correct answer is C) dead reckoning position. A chart position enclosed by a semi-circle indicates a dead reckoning position, which is calculated based on the vessel's course, speed, and elapsed time, without the benefit of a visual or electronic fix. This is in contrast to a fix (option A), which is a position determined by visual bearings, electronic positioning systems, or other external references, or an estimated position (option B), which incorporates some external data into the position calculation. A running fix (option D) involves taking multiple fixes over time to determine a vessel's position, rather than a single dead reckoning position.