Running Fix

One useful technique for fixing your position at sea with only one charted landmark is called a “running fix.” This method helps navigators determine their location over time, compensating for their vessel’s movement.

What is a Running Fix?

A running fix is a method used in navigation to determine a vessel’s position when a single position fix cannot be obtained. This might occur because of continuous movement, poor visibility, or inadequate positioning of navigational aids. By taking two or more bearings from known points at different times and then plotting these on a chart relative to the movement of the vessel, navigators can estimate their current location.

Step-by-Step Process to Take a Running Fix

1. Obtain Initial Bearing: Start by taking a bearing of a known visible landmark or navigational aid using a compass or a radar. Make sure to note the exact time when the bearing was taken.
   
2. Record Your Course and Speed: After taking the initial bearing, continue to monitor and record your vessel’s course and speed. This information is crucial for accurately plotting your movement on the navigation chart.
   
3. Take A Subsequent Bearing: After a predetermined period, usually an hour or half an hour depending on your speed and the accuracy required, take another bearing of the same landmark. Record the exact time of this second observation as well.
   
4. Plot the Bearings on a Chart: Use a nautical chart to plot both bearings along with the times they were taken. Draw lines along the bearing directions from the respective landmarks.
   
5. Adjust for Movement: To account for your vessel’s movement between the two bearing recordings, you need to adjust the position of the first bearing line. Calculate how far your ship has traveled in the direction of its heading between the two bearings, and move the first line accordingly on the chart. This is typically done by marking the distance traveled from the initial point along the course line and then drawing a parallel line to the initial bearing.
   
6. Determine Your Position: The intersection of the adjusted first bearing and the second bearing line will give you your current position. This is your running fix.
   

Conclusion

Taking a running fix is a vital skill for any navigator, ensuring safety and accuracy in open waters. By practicing this method, mariners can improve their proficiency in navigation and ensure they always have a reliable method to determine their position, especially when other modern equipment might fail or provide insufficient data. Whether you’re navigating a small yacht or managing a large commercial vessel, mastering the running fix is an invaluable part of your maritime skillset.