If you can maintain a consistent boat speed AND an unwavering boat heading, then the running fix can get you a better position fix than just using your dead reckoning positions. There may be a current pushing you off course, or the wind may be causing you to drift so you’re never going to be where your DR says you should be. When taking bearings, it’s best to use landmarks that are fixed, like a really obvious tower or lighthouse. Don’t use another moving boat!
There is sure to be at least one of these kinds of questions on any Coastal Navigation Exam, and it behooves you to practice it often. When I was taking my American Sailing Association level 105 with the Maryland School of Sailing, this kind of question really tripped-up the students. It wasn’t until I just gave in, and instead of understanding the why of the geometry, I just decided to memorize the how. So, I wrote myself a step-by-step cheat-sheet of procedure and just performed the answer like a choreographed dance using rulers, pencil and dividers instead of feet, arms and hips!
Hopefully this little step by step, 5,6,7,8 will prevent you from breaking out into a cold sweat every time you come across a Running Fix question and help put the sparkle back in your navigation plotting “jazz hands”!
The video below works through the practice question using the Training Chart 1210Tr. The diagrams below are just references and do not necessarily relate to the practice question, but it’s pretty similar!