What should be used as a new course line when plotting from each fix or running fix?

When plotting a new course line from each fix or running fix, utilizing a minimum of two Dead Reckoning (DR) positions ensures a more accurate and reliable determination of the vessel's course and speed. This practice helps account for any discrepancies or errors in navigation by providing a reference point that reflects how the vessel has been traveling over time.

Using just one DR position could result in inaccuracies since it does not take into consideration the vessel's previous course or any changes that might have occurred. A historical fix might not accurately represent the current position or conditions affecting navigation. Focusing solely on the recent course change could lead to overlooking valuable data from earlier positions that might be significant for making a comprehensive navigational decision.

In summary, requiring a minimum of two DRs provides a more stable foundation for plotting a new course line, incorporating both the vessel's recent navigation history and current trajectory, ultimately enhancing the accuracy of navigational plotting.