Charting Your Course: DR, Running Fix, and EP - The Navigator’s Essentials

Long before GPS became standard on every helm, sailors relied on the chart table, parallel rulers, dividers, and a sharp pencil to know exactly where they were. And even today ...whether you’re offshore, racing, or simply want to keep your seamanship skills sharp... traditional charting remains a vital part of good seamanship. Three of the foundational tools in this craft are the Dead Reckoning (DR) position, the Running Fix (RFix), and the Estimated Position (EP). Each marks a different way of keeping track of your course, and understanding them ensures you can navigate with confidence no matter what the sea throws your way.

Below, we break down each method in clear, sailor-friendly terms, just as you’d practice them at the chart table with a fresh mug of Skipper’s Remedy® by your side.

Dead Reckoning (DR): Tracking Course, Speed, and Time

A Dead Reckoning position is one of the most fundamental plotting tools in navigation. It predicts where your vessel should be based purely on your last known position, the course you’re steering, your speed, and the time elapsed ...without accounting for wind, current, or leeway.

To mark a DR on your chart:

1. Start with a known point such as a GPS fix, visual bearings, radar, or even a previous DR. Mark it clearly.

2. Record your course steered and speed in your log.

3. Calculate distance run using distance = speed × time.

4. Plot your course line using parallel rulers.

5. Measure and mark the distance along that line with dividers.

6. Label your DR with the time and “DR,” and mark the point with a semicircle open toward your direction of travel.

DRs are typically plotted every hour or after any change in course or speed. Together, they form the backbone of your expected track ...a predictive trail that becomes crucial when conditions reduce visibility or electronics go down.

Running Fix (RFix): Using LOPs When Only One Object Is Visible

When you can’t get simultaneous bearings on multiple objects ...say only one lighthouse or tower is in view... you can still determine a fix by taking bearings of the same object at two different times. This is called a Running Fix, or RFix.

A Running Fix works like this:

1. Take your first bearing, convert it to true, and plot your first Line of Position (LOP). Label it with the time.

2. Dead reckon forward to the later time using your course and speed.

3. Advance the first LOP to this new time by moving it parallel to itself by the DR distance.

4. Take your second bearing at the later time and plot the second LOP.

5. Where the advanced LOP and the new LOP intersect ...that’s your RFix.

Mark it with a circle and label it “RFix” and the time.

A Running Fix is invaluable during coastal cruising or racing when landmarks fade in and out of view or when conditions don’t allow a full three-bearing fix.

Estimated Position (EP): Adjusting Your DR for Real-World Forces

While DR gives you a predicted position, the ocean rarely behaves perfectly. Wind, waves, and current all push your vessel off its ideal track. When you account for these influences, you get an Estimated Position (EP) ...a more realistic approximation than a pure DR.

To plot an EP:

1. Start with your DR.

2. Apply leeway, marking how the wind pushes your vessel sideways.

3. Apply set and drift, plotting how the current moves you over time. Set is the direction a current flows (in degrees), and Drift is the speed of that current (in knots).

4. Mark the corrected point and draw a small square around the dot ...this is the traditional EP symbol.

EPs are especially important in areas with strong tidal currents, heavy winds, or coastal hazards. They help you navigate safely between fixes while staying aware of how environmental forces shape your true path.

Why Traditional Charting Still Matters

Even with the convenience of GPS, sailors who understand DR, RFix, and EP have a deeper connection to their navigation and a stronger ability to troubleshoot when technology can’t be trusted. Offshore sailors rely on these skills daily, and even weekend cruisers benefit from knowing how to keep track of their position with nothing but pencil and paper.

At Skipper’s Remedy®, we believe seamanship and great coffee go hand in hand. Whether you're plotting a DR in your cabin at dawn, taking bearings from the cockpit, or reviewing your course over a warm mug during the night watch, these timeless tools keep you safe and connected to the traditions of the sea. Explore our Navigator's Reserve - a new limited-edition roast each month and Charted Indulgence - Dubai Chocolate roast.

Fair winds, clear charts, and bold brews.
-from the crew at Skipper’s Remedy®