Traditional Piloting: Putting It Together
Navigating a coastal passage using only traditional tools
Before Departure: Chart Preparation
Every successful coastal passage begins at the chart table before you leave the dock. Lay out the paper charts covering your entire route and draw the intended track from departure to destination. Using parallel rulers and dividers, measure the true course for each leg and convert it to a magnetic course using the local variation. Note the distance of each leg in nautical miles alongside the course label. This pre-departure plotting is the foundation of everything that follows — errors made here propagate through the entire passage.
Identify the landmarks and aids to navigation you will use for visual fixes along each leg. Mark prominent features — lighthouses, water towers, headlands, church spires — with small circles or notes on the chart. Pre-select the pairs or triplets of landmarks that will give good fix geometry (intersections near 90 degrees are ideal). Note the expected bearing ranges for each landmark so that when you are underway, you already know which objects to look for and roughly where they should bear.
Before leaving, establish danger bearings and clearing marks for any hazards along the route. A danger bearing is a bearing to a known landmark that, if exceeded, tells you that you have strayed into dangerous water. A clearing mark is a pair of charted objects that, when held in transit, keep you on a safe track. Pre-plot these on the chart in red pencil so they are immediately visible when you glance down during the passage. Also note minimum safe depths for each leg and mark any areas where the depth will shoal unexpectedly.
Use a soft pencil (2B) for chart work so you can erase and re-plot without damaging the chart surface. Keep a good eraser, parallel rulers, dividers, and a pencil sharpener in your chart table kit at all times.
Departure Fix and Initial DR
As you clear the harbor entrance, take your departure fix — the last precisely known position before the open-water passage begins. This fix should come from at least two (preferably three) visual bearings on charted objects taken in quick succession. Plot these lines of position on the chart, mark the intersection with a circle and the time, and label it clearly as the departure fix. This position is the anchor point for your entire DR plot — every estimate that follows depends on its accuracy.
From the departure fix, lay out your first DR leg along the planned course. Note the time of departure, your compass heading (magnetic), the log reading or estimated speed, and any initial observations about wind and sea state in the logbook. Every entry should include: time, log reading, course steered (compass and magnetic), wind direction and strength, barometric pressure, and any remarks. Disciplined log-keeping is what separates competent navigators from those who are merely lucky.
Start your DR plot by drawing the course line from the departure fix and marking an initial DR position at a convenient interval — typically 15 or 30 minutes from departure depending on the proximity of hazards. Label the course line with the course (e.g., 'C 085 M') and speed (e.g., 'S 6.2'). As you settle onto the course, verify that the compass heading holds steady and that the speed through the water matches your estimate. Any discrepancy noted early can be corrected before it compounds into a significant error.
Never assume your departure fix is accurate without verifying it. If the three LOPs do not form a tight triangle (a 'cocked hat' larger than a few hundred meters), something is wrong — recheck your bearings and identification of landmarks before proceeding.
Why is the departure fix considered the most critical fix of a coastal passage?
A 'cocked hat' that is very large after plotting three bearings most likely indicates:
Maintaining the DR Track
Once underway, the DR track must be maintained continuously. At every course change, mark the DR position on the chart with a semicircle and the time, then draw the new course line from that point. Record the course change in the logbook with the time, new heading, reason for the change, and the log reading or estimated distance run on the previous leg. Between course changes, mark DR positions at regular intervals — every 30 minutes in pilotage waters, every hour on longer coastal legs. Each DR position is calculated from the previous one using the formula: distance = speed x time.
Leeway correction must be applied whenever the boat is sailing at an angle to the wind. Leeway is the sideways drift caused by wind pushing the boat to leeward. Most sailing vessels experience 3 to 7 degrees of leeway when close-hauled, and less on broader points of sail. Apply leeway as a correction to the course steered: if the wind is from port, the boat is being pushed to starboard, so add the leeway angle to the course to get the course made good. If the wind is from starboard, subtract it. Log the estimated leeway alongside the course.
Discipline is key. It is tempting to skip DR updates when conditions are easy and the coast is clearly visible, but the habit of regular plotting pays off when visibility suddenly drops or you enter an unfamiliar area. Every DR position on the chart is a record of where you believe the boat has been — if you need to reconstruct your track after the fact (for example, to diagnose a grounding or to report a sighting), the DR plot and logbook are your evidence. Treat them as a professional obligation, not a chore.
When estimating leeway, observe the angle between the wake and the centerline of the boat. In most conditions, the wake gives a reasonable visual estimate of leeway within a degree or two.
Taking Fixes Underway
The DR track tells you where you should be; a fix tells you where you are. The workflow for taking a fix underway is: identify landmarks, take bearings, plot on chart, label the fix, compare to DR, and assess set and drift. Begin by selecting two or three charted objects that are clearly visible and well-distributed around the compass (ideally 60 to 120 degrees apart). Take compass bearings to each object in quick succession — the fastest-moving bearing first (the one nearest abeam) and the slowest-moving bearing last (the one nearest ahead or astern).
Convert each compass bearing to a true bearing by applying deviation (from the deviation card for the heading being steered) and variation (from the compass rose on the chart). Plot each bearing as a line of position (LOP) from the charted landmark. The intersection of two LOPs gives a fix; three LOPs give a fix with a built-in accuracy check (the size of the cocked hat). Mark the fix with a circle, note the time, and label it. Then measure the distance and bearing from your DR position at that time to the fix — this vector represents the set and drift the vessel has experienced since the last correction.
How often should you take fixes? In open coastal waters with no nearby hazards, every 30 to 60 minutes is adequate. In restricted waters, near headlands, or when approaching port, fix as often as every 10 to 15 minutes. The general rule is: the closer the hazard, the more frequently you fix. Each fix resets the DR — after plotting a fix, the next DR leg starts from the fix position, not from the previous DR. This prevents cumulative error from compounding over the passage.
Always take the bearing to the object whose angle is changing fastest first (typically the one nearest abeam). If you take the slow-changing bearing first and the fast-changing one last, the time delay between observations introduces position error.
When taking a round of bearings for a fix, which landmark should you observe first?
After plotting a new fix, where does the next DR leg start?
Correcting for Set and Drift
When your fix does not agree with your DR position — and it almost never will exactly — the difference is caused by set and drift. Set is the direction toward which the current or combined forces have pushed the boat, measured as a true bearing. Drift is the speed of that displacement, measured in knots. To calculate them, measure the bearing and distance from the DR position at the fix time to the actual fix. If your DR said you should be at point A, and the fix puts you at point B, the bearing from A to B is the set, and the distance from A to B divided by the time since the last fix gives the drift.
Once you know the set and drift, you can apply a correction to the next leg to compensate. The method is called the CTS (Course to Steer) calculation. On the chart, draw a line from your current fix to the next destination point — this is the course made good (CMG) you want to achieve. From the fix, draw the set and drift vector for the expected time of the leg. From the end of that vector, use dividers to swing an arc equal to your boat speed multiplied by the time of the leg. Where the arc intersects the CMG line determines the course to steer. This vector triangle — current, boat speed, and resultant track — is the core of coastal passage planning.
In practice, set and drift are not constant. Tidal currents change direction and strength throughout the tide cycle, and wind-driven current varies with wind strength and duration. Re-assess set and drift at every fix and adjust the CTS accordingly. On a long coastal passage, you may recalculate CTS several times as the tide turns. Keeping a running record of observed set and drift in the logbook helps you anticipate changes and plan ahead for the next leg.
If set and drift are consistent over several fixes, you can predict the correction needed for future legs. But always verify with the next fix — conditions change, especially around headlands and in tidal narrows.
Arrival and Final Approach
The approach to your destination harbor is the most critical phase of the passage — water shoals, traffic converges, and landmarks are often harder to identify against a cluttered shoreline. Begin your approach preparations well before arrival. Review the chart for the harbor entrance, noting the approach bearing, any leading lines or range marks, lateral buoys, and minimum depths. If you pre-plotted danger bearings during chart preparation, now is the time they earn their keep — monitor the bearing to the reference landmark and confirm it stays on the safe side of the danger bearing.
As you close with the coast, increase your fix frequency to every 10 to 15 minutes, or more often in restricted waters. Use depth soundings as an additional check on your position — compare the depth reading to the charted depth at your estimated position, corrected for the height of tide. If depth and visual fixes agree, you have high confidence in your position. If they disagree, slow down and investigate before proceeding. Identify the harbor entrance marks — the port and starboard lateral buoys or beacons — and confirm they match the chart and the pilot book description.
Take a final fix before entering the harbor channel. This fix should use landmarks that give the best geometry relative to the entrance — objects that confirm you are on the correct approach line and at the correct distance from the entrance. Once you enter the channel, navigation transitions from pilotage to close-quarters maneuvering, and your focus shifts to the marks immediately ahead. Record the final fix time and position in the logbook, along with your arrival time. The passage is complete — and every position, course change, and fix is documented in the chart plot and logbook for review.
Never rely on a single source of information during the approach. Cross-check visual bearings with depth, compare your fix to the DR, and verify that buoy colors and shapes match the chart. If anything does not add up, stop and reassess before proceeding into shallow water.
A danger bearing is used during the approach to:
Why should you increase fix frequency during the approach to port?
Summary
A complete traditional coastal passage relies on thorough chart preparation before departure — pre-plotting courses, distances, danger bearings, and identifying landmarks for visual fixes.
The departure fix anchors the DR plot, and disciplined log-keeping records every course change, speed, and time for continuous DR maintenance throughout the passage.
Regular visual fixes underway reveal set and drift, allowing the navigator to calculate a corrected course to steer (CTS) for each subsequent leg using vector triangle methods.
The approach and arrival phase demands the highest vigilance — increased fix frequency, depth cross-checks, danger bearing monitoring, and positive identification of harbor entrance marks before entering the channel.
Key Terms
- Departure Fix
- The precisely plotted position taken as the vessel leaves harbor, serving as the anchor point for the entire DR track that follows.
- Danger Bearing
- A pre-plotted bearing to a charted landmark that defines the boundary between safe and dangerous water; as long as the observed bearing stays on the safe side, the vessel is clear of the hazard.
- Course to Steer (CTS)
- The compass heading calculated by applying set and drift corrections to the desired course made good, ensuring the vessel tracks toward the intended destination despite current.
- Set and Drift
- Set is the direction toward which the current moves the vessel (true bearing); drift is the speed of that displacement (knots). Together they describe the current's effect on the vessel's track.
- Cocked Hat
- The triangle formed when three lines of position do not intersect at a single point. A small cocked hat indicates a good fix; a large one suggests an error in one or more bearings.
- Clearing Mark
- Two charted objects that, when kept in transit (aligned), define a line that keeps the vessel clear of a specific hazard.