Coastal Piloting & Inland Waters
Master lines of position, visual bearings, danger bearings, current effects, narrow channel rules, and GPS navigation for the USCG OUPV captain's license exam.
1. Piloting Fundamentals — LOP, Fix, and Position Types
Piloting is the art of navigating by reference to charted objects — landmarks, buoys, depth contours, and ranges. The line of position (LOP) is the building block of all piloting. A single LOP tells you that your vessel is somewhere on that line. Two or more LOPs give you a fix.
What is a Line of Position (LOP)?
An LOP is any line on the chart on which your vessel must be located. Sources of LOPs include:
Position Type Comparison
| Type | Symbol |
|---|---|
| Fix | Circle ○ |
| Running Fix | Circle ○ with R |
| Estimated Position (EP) | Square □ |
| Dead Reckoning (DR) | Half-circle ⌓ |
Draw LOPs from each charted object through their reciprocal bearings. Where they intersect, draw a small circle. Write the time alongside: 1423. If three LOPs form a small triangle (cocked hat), your fix is at the center.
From last fix, draw your course line. Mark your speed along it for each time interval. Use a half-circle symbol. Label course over the line (C 090) and speed below (S 6). DR is your baseline — fix it whenever possible.
From your DR position, draw the current vector (set direction, drift distance). The tip of the current arrow is your EP. Mark it with a square. The EP is always preferred over a bare DR when current is known.
2. Visual Bearings — Three-Bearing Fix and Running Fix
Hand Bearing Compass Technique
The hand bearing compass is the most fundamental piloting instrument. Hold it steady at eye level away from metal objects. Take simultaneous (or near-simultaneous) bearings on two or more charted objects. Convert to true bearings if needed (subtract variation and deviation). Plot the reciprocals from the objects.
For the best two-LOP fix, choose objects roughly 90 degrees apart (60–120 degrees is acceptable). For a three-LOP fix, choose objects approximately 120 degrees apart. Bearings nearly parallel to each other create a very elongated cocked hat with high position uncertainty.
True = Magnetic + Variation. Magnetic = Compass + Deviation. The mnemonic: Can Dead Men Vote Twice? (Compass, Deviation, Magnetic, Variation, True) — add easterly corrections, subtract westerly. Most hand bearing compasses read magnetic; variation is applied from the chart compass rose.
Three-Bearing Fix
A three-bearing fix is more reliable than a two-bearing fix because it reveals errors — if all three LOPs cross at exactly one point, your bearings are accurate. If they form a triangle (cocked hat), position yourself inside the triangle on the side closest to the nearest danger.
- Choose three charted objects approximately 120 degrees apart
- Take bearings on all three as nearly simultaneously as possible
- Convert to true bearings
- On the chart, draw a line through each object in the direction of the reciprocal bearing
- If three LOPs cross at one point: excellent fix, mark with circle and time
- If a small triangle forms: your position is within the triangle; favor the dangerous side for safety
- If a large triangle: one or more bearings are in error — retake them
Running Fix — Advancing an LOP
When only one object is visible, use a running fix. Take a bearing, run on your course and speed, take a second bearing, then advance the first LOP to the time of the second.
| Step | Action |
|---|---|
| 1 | Take a bearing on the object and note the time. Plot the LOP on the chart. |
| 2 | Continue on your course. Note exact course steered and log speed. |
| 3 | After running a suitable distance, take a second bearing on the same object. Note the time. |
| 4 | Calculate distance run: speed multiplied by time elapsed. |
| 5 | Draw an arrow from any two points on the first LOP, parallel to your course, the length of the distance run. |
| 6 | Draw the new position of the advanced LOP through the tips of those arrows, parallel to the original LOP. |
| 7 | Where the advanced LOP crosses the second LOP is your running fix. Mark with circle and time of second bearing. |
3. Ranges — Natural Ranges and Range Lights
A range is one of the most accurate LOPs available. When two charted objects appear in line (one behind the other from your position), your vessel is on the exact line connecting them. No compass is needed — ranges are compass-independent and immune to variation and deviation errors.
Natural Ranges
Any two charted objects that happen to line up can serve as a natural range. Examples:
- · A lighthouse and a chimney in line
- · A daymark and a water tower
- · A church steeple and a hilltop
- · Two buoys (less reliable — they swing on their moorings)
Check that both objects are plotted accurately on the chart before trusting the range.
Range Lights
Range lights are intentionally established pairs of lights to mark a channel centerline. The rear light is higher and farther back; the front light is lower and closer to the water. When both lights are vertically aligned, you are on the range (channel centerline).
- · Front light: lower, closer, often isophase or fixed
- · Rear light: higher, farther, same color as front
- · If rear appears left of front: you are right of centerline
- · If rear appears right of front: you are left of centerline
Using a Range for Channel Entry
Range lights and natural ranges are ideal for entering a channel because they give continuous, real-time guidance with no instruments. The procedure:
- Identify the front and rear range markers on your chart and by sight
- Approach with both lights in line (vertically stacked) — you are on the centerline
- If the rear light opens to the left, steer left to return to centerline
- If the rear light opens to the right, steer right to return
- A range LOP is a single precise line — cross it with a depth sounding or a bearing for a two-LOP fix
- Note the charted bearing of the range for use as an LOP when plotted on the chart
4. Depth Contour Navigation — Sounding Checks and Lead Line
Following a Depth Curve
In restricted visibility or when visual bearings are unavailable, you can navigate by matching your echosounder readings to a specific depth contour on the chart. This technique, sometimes called 'contour piloting' or 'bathymetric navigation', requires a chart with sufficient sounding data and a recognizable contour line.
- · Identify a distinctive depth contour that parallels your route
- · Steer to maintain constant echosounder reading
- · If depth shoals: steer toward deeper water
- · If depth deepens: steer toward shallower water
- · Use it as a single LOP — cross with a bearing for a fix
Chart soundings are referenced to MLLW (Mean Lower Low Water). To compare your echosounder to chart depths, subtract the tidal height from your sounding. If tide is +3 feet and you read 18 feet, the charted depth is approximately 15 feet. Confirm your echosounder draft offset is correctly set.
Sounding Checks
Periodic sounding checks are a safety habit for any coastal passage. As you approach a charted shoal or shoaling area, increased sounding frequency gives early warning. The exam expects you to know:
- · Soundings on NOAA charts are in feet (coastal) or fathoms (offshore)
- · 1 fathom = 6 feet
- · Bold contour lines indicate major depth changes (e.g., 6-fathom curve)
- · Corrected depth = echosounder reading + draft - tidal height
Lead Line
The lead line is a weighted line marked in fathoms and feet, used before electronic depth sounders. The lead (weight) has a hollowed bottom filled with tallow — pressing bottom sediment into the tallow allowed the navigator to determine bottom type (sand, mud, gravel, shell) to compare with chart notations.
- · Traditional markings: 2, 3, 5, 7, 10, 13, 15, 17, 20 fathoms
- · 'Mark' means an exact fathom mark; 'deep' means between marks
- · 'By the mark five' = exactly 5 fathoms
- · Still required as backup on some commercial vessels
5. Danger Bearing — Clearing Lines and Safe Sectors
A danger bearing is a predetermined bearing from a charted object that defines the boundary between safe water and a hazard. It is one of the most important safety tools in coastal piloting and is heavily tested on the OUPV exam.
Drawing a Danger Bearing
- Identify the hazard (rock, shoal, reef) on the chart
- Identify a nearby charted landmark visible from seaward
- Draw a line from the charted landmark through the outer edge of the hazard
- Measure the true bearing of this line from the landmark
- Label it NLT or NMT followed by the bearing and the landmark name
- Monitor your hand bearing compass continuously while passing
Using NLT and NMT
The label tells you which direction to maintain the bearing:
- NLT (Not Less Than): Keep the bearing equal to or greater than this value. Used when the hazard is to the right of the safe bearing — if the bearing decreases, you are moving toward the danger.
- NMT (Not More Than): Keep the bearing equal to or less than this value. Used when the hazard is to the left — if the bearing increases, you are moving toward the danger.
Clearing Lines and Safe Sectors
A clearing line is a line drawn on the chart beyond which all dangers are clear. You stay on the safe side of the clearing line at all times. Safe sectors are defined by two clearing bearings — the angular range in which it is safe to approach.
One line defines the limit. Stay on the safe side (NLT or NMT).
Two clearing bearings define a safe angular window for approach.
A minimum or maximum distance off a point, used with radar or range arcs.
6. Estimated Position vs. Fix — DR Accuracy and Current Correction
The DR position degrades with time. Sources of DR error accumulate: compass deviation, helmsman inaccuracy, log error, and most importantly — current. An EP accounts for current and is always preferred over a bare DR when current data is available.
- · Compass error (variation + deviation uncorrected)
- · Leeway (wind pushing vessel sideways)
- · Current set and drift (biggest single error source)
- · Log/GPS speed error
- · Helmsman steering error (off course by 2-5 degrees)
- · Tidal stream variations from predicted values
- Plot your DR position for the time of interest
- From the DR position, draw the current vector
- Set = direction current flows toward
- Drift = current speed in knots multiplied by hours elapsed
- The tip of the current arrow is your EP
- Mark EP with a square; fix it with the next available LOP
You have been on course 090T at 6 knots for 2 hours since your last fix. Current is set 180T (southward) at 1.5 knots. Your DR position is 12 nm east of the fix. The current has pushed you 1.5 knots south for 2 hours = 3 nm south. Your EP is 12 nm east and 3 nm south of your last fix. You are south of your intended track — you should steer slightly north to compensate or allow for this drift in your ferry angle calculation.
7. Current Effects on Track — Set, Drift, Ferry Angle, and Leeway
Set and Drift Defined
Set is the direction toward which the current flows. A current setting 270T flows toward the west. Set is given in degrees true, using the 'toward' convention (opposite of wind direction convention — winds are named for where they come from).
Drift is the speed of the current in knots. A drift of 2 knots means the water is moving 2 nautical miles per hour in the set direction.
- · Compare GPS track (COG) to compass course (heading): difference reveals leeway + current
- · Compare GPS speed (SOG) to knotmeter: difference may include current component
- · Compare fix to DR position: the vector from DR to fix = combined current effect
- · Refer to tidal current tables and current charts for predicted values
- · Observe current at fixed buoys: leaning and wake reveal set and rough drift
The Current Triangle
The current triangle is the graphical solution to the three-vector problem: vessel speed and heading, current set and drift, and resulting course and speed made good. Solving it yields the ferry angle (crab angle) needed to maintain a desired track.
| Step | Action |
|---|---|
| 1 | Draw your intended track (Course to Make Good, CMG) on the chart |
| 2 | From the starting point, lay off the current vector: direction = set, length = drift (knots × time) |
| 3 | From the tip of the current vector, swing an arc equal to your vessel speed |
| 4 | Where the arc intersects the track line is the theoretical position made good |
| 5 | Draw a line from the current vector tip back to the starting point — that is your course to steer (CTS) |
| 6 | The angle between CMG and CTS is the ferry angle (crab angle) |
| 7 | The distance from start to the track intersection divided by time = speed made good (SMG) |
Leeway vs. Current
8. Narrow Channel Navigation — Rule 9 and Traffic Separation
Rule 9 of the ColRegs (and Inland Rules) governs narrow channel navigation. It is one of the most tested rules on the OUPV exam because it overrides many general right-of-way rules.
| Rule 9 Requirement | Detail |
|---|---|
| Keep to starboard | Stay as far to the starboard side as safe and practicable |
| Small vessels yield | Vessels under 20m or sailing vessels must not impede a vessel that can safely navigate only within the channel |
| Crossing vessels yield | A vessel crossing a narrow channel must not impede a through-channel vessel |
| Overtaking | Only when the vessel ahead signals willingness; Inland Rules require whistle signal exchange |
| Fishing vessels | Fishing vessels must not impede the passage of other vessels navigating in a narrow channel |
| Anchorage | Vessels should not anchor in a narrow channel except in an emergency |
| Lookout | Enhanced lookout required; bends and sharp turns require slow speed and sound signals (Rule 34d: one prolonged blast before entering a blind bend) |
Traffic Separation Schemes (TSS)
Traffic Separation Schemes are designated shipping lanes in high-traffic areas. Rule 10 governs TSS compliance:
- · Vessels follow the appropriate traffic lane for their direction
- · Join or leave at the ends of lanes when practicable
- · When crossing a TSS: cross at right angles to the flow
- · Small vessels, sailing vessels, and fishing vessels should avoid TSS lanes when practicable
- · Do not anchor in a TSS or separation zone
- · The separation zone between lanes must not be used except in emergency
Fairways and Recommended Routes
Fairways are charted preferred routes in harbor approaches and coastal waters. They differ from traffic separation schemes in that they are less formal:
- · Deep-draft vessels have priority in charted fairways
- · Small recreational vessels should stay out of main ship channels when possible
- · Precautionary areas: zones where vessels must proceed with caution
- · Inshore traffic zones: for vessels that need not use the main TSS lanes
- · Charted with magenta boundaries and arrow markings
- · A 15-meter vessel cannot impede a 40-meter vessel navigating within a narrow channel — even if the 15-meter vessel is the stand-on vessel in a crossing situation
- · A sailing vessel has NO special privilege in a narrow channel over a power vessel that can only navigate within the channel
- · Rule 9 does NOT eliminate general steering rules — it adds the 'shall not impede' obligation on top of them
- · Sound one prolonged blast before entering a bend that obscures other vessels (Rule 34d)
9. Anchoring for Piloting — Using the Hook as a Position Tool
An anchor can be a precision piloting tool, not just a hotel. In tight quarters — waiting for a bridge opening, a fair tide, or reduced fog — anchoring allows you to hold your position precisely while you gather information, plot your approach, or wait for safer conditions.
- · Select a charted anchorage with adequate depth and swinging room
- · Scope: minimum 5:1 in calm conditions, 7:1 in moderate conditions
- · Take bearings on two or more fixed charted objects immediately after anchoring
- · Plot your anchor position and draw your swing circle
- · Recheck bearings periodically to confirm you are not dragging
- · Use GPS anchor alarm if available, but verify visually as well
- · In restricted width, use a Bahamian moor (two anchors, fore and aft) to limit swing
- · Set bow anchor first, drop back, set stern anchor
- · This halves your swing radius — critical in narrow creeks and commercial anchorages
- · Check your swing circle does not overlap with other vessels
- · Sound anchor scope appropriate to expected current changes with tide
10. Coastal Waypoint Navigation — GPS, XTE, and Approach Angles
GPS Waypoint Sequencing
Modern coastal piloting uses GPS waypoints to define a route. The chartplotter sequences through waypoints automatically, displaying bearing to the next waypoint (BTW), cross-track error (XTE), and estimated time of arrival (ETA). But GPS has limits — always verify your GPS track against your paper chart and visual observations.
- · Place waypoints in safe, clear water — never on a hazard
- · Set waypoints at every course change
- · Set approach waypoints 0.5-1 nm short of harbor entrances
- · Include a waypoint for each buoy you must round
- · Verify all waypoints against the current chart before departure
- · Do not blindly navigate to a waypoint — watch your surroundings
- · COG (Course Over Ground): actual direction of movement
- · SOG (Speed Over Ground): actual speed including current
- · BTW (Bearing to Waypoint): compass bearing to next waypoint
- · DTW (Distance to Waypoint): remaining distance
- · XTE (Cross-Track Error): perpendicular distance off track
- · VMG (Velocity Made Good): speed toward destination
Cross-Track Error (XTE) Management
| Display | Meaning | Action |
|---|---|---|
| XTE 0.0 | On track centerline | Maintain current heading |
| XTE 0.2L | 0.2 nm left of track | Alter course to starboard to return to track |
| XTE 0.5R | 0.5 nm right of track | Alter course to port; check for current effect |
| XTE 1.0R (increasing) | Far right and moving farther right | Significant course correction needed; check chart for hazards |
Approach Angle and Harbor Entry
When approaching a harbor or inlet, the approach angle determines your exposure to breaking waves and cross-current. Standard practice:
- · Enter an inlet on a heading perpendicular to the bar (directly into or with following seas) — never broadside to breaking waves
- · Check the current direction: entering against an outflowing current reduces wave height; entering with current can increase wave period but steepen them
- · Watch for range lights marking the channel centerline — use them in preference to GPS when available
- · In shoaling inlets, the channel shifts — verify your GPS waypoints against the most recent NOAA survey
- · Call the local harbor master on Ch 16 for current conditions before entering an unfamiliar inlet
11. Bridge-to-Bridge VHF Procedures
VHF radio is mandatory on most vessels operating in coastal and inland waters. The Bridge-to-Bridge Radio Telephone Act requires vessels of certain sizes to maintain a watch on Channel 16 and carry bridge-to-bridge radio equipment. The OUPV exam tests proper radio procedures, channel usage, and distress communications.
| Procedure | Channel |
|---|---|
| Calling a vessel | Ch 16 |
| Security call (traffic) | Ch 16 |
| Mayday | Ch 16 |
| Pan-Pan (urgency) | Ch 16 |
| Bridge opening request | Ch 9 or local |
| Coast Guard traffic check | Ch 22A (after Ch 16) |
Immediate threat to life or vessel. Highest priority. All other stations must stand by.
Urgent message about safety of vessel or person. Below Mayday threshold.
Navigation safety message: traffic announcement, hazard to navigation.
12. Night Piloting — Light Identification and Leading Lights
Night Visual Environment
Night piloting demands disciplined technique. Your eyes need 20-30 minutes to fully dark-adapt — avoid white light exposure. Use red light for chart work. Scan the horizon systematically. Distant lights appear intermittent before they are close enough to observe reliably.
- · Close one eye when using a flashlight — preserve adaptation in the other
- · Use red-filtered chart lights exclusively
- · Shield radar and chartplotter brightness to minimum
- · Scan with peripheral vision — rods (night vision cells) are off-center
- · Allow 30 minutes after departure from well-lit dock
- · Time the period with a stopwatch (one full cycle)
- · Count flashes per group carefully
- · Note color: white, red, green, yellow
- · Match against the Light List for your area
- · Confirm nominal range matches the chart
- · Do not confuse navigation lights with shore lights
Light Characteristics Reference
| Abbrev. | Name |
|---|---|
| F | Fixed |
| Fl | Flashing |
| Oc | Occulting |
| Iso | Isophase |
| Q | Quick |
| VQ | Very Quick |
| Mo(A) | Morse Code A |
| Al.WR | Alternating |
Leading Lights
Leading lights are range lights used for channel approach at night. They work identically to daytime range markers: when the front and rear lights are vertically aligned, you are on the centerline of the channel approach. The leading line bearing is charted. Leading lights are often shown as a white sector flanked by red and green sectors to indicate the channel limits.
Sector Lights
A sector light shows different colors through different arcs of bearing. The white sector indicates safe water; red sectors indicate danger to port or danger ahead; green sectors indicate danger to starboard. Sail or motor through the white sector to stay in safe water. Chart annotations show the degree limits of each color sector.
- · Always confirm at least two charted lights before assuming you know your position
- · A light not on the expected bearing may mean you are off course — do not assume chart error
- · Distance to a light: luminous range is not geographic range — a light's stated range assumes good visibility
- · Dipping range: the range at which a light just appears or disappears over the horizon, calculable from light height and eye height
- · False lights: shore lights, vehicle lights, and other vessels can be confused with navigation lights — time and verify
13. Practice Problems with Solutions
These problems cover the most commonly tested piloting scenarios. Work through each one before revealing the solution.
PP1You are bearing on a lighthouse at 045T and simultaneously on a water tower at 315T. Your chart shows these objects plotted. What type of position do you have, and how do you plot it?+
You have a fix — two simultaneous LOPs from two independent objects. Plot a line from the lighthouse along the reciprocal bearing (045 + 180 = 225T, so the LOP runs from the lighthouse at 225T toward your vessel, meaning your vessel is on a line bearing 045T from the lighthouse). Do the same for the water tower: your LOP runs on bearing 315T from the tower. Where the two lines intersect is your fix. Mark it with a circle and the time (e.g., 1315). A two-LOP fix gives a single point; a three-LOP fix typically creates a small triangle (cocked hat) — plot your position at the center.
PP2The current is setting 090T at 2 knots. You want to make good a track of 000T at 8 knots vessel speed. What course should you steer and what is your speed made good?+
The current is pushing you 90 degrees to the right of your track. Ferry angle = arcsin(2/8) = arcsin(0.25) = approximately 14.5 degrees. Steer 000 - 14.5 = 345.5T (into the current, which is from the east, so steer slightly west of north). Speed made good = square root of (8 squared minus 2 squared) = square root of (64 - 4) = square root of 60 = approximately 7.75 knots. On the exam, use the current triangle method on the plotting sheet for precise answers.
PP3You observe a lighthouse and take a bearing of 270T. You continue on course 000T at 6 knots for 30 minutes, then take another bearing on the same lighthouse: 225T. What is your running fix position?+
Advance the first LOP. In 30 minutes at 6 knots, you traveled 3 nautical miles on course 000T. Draw the first LOP (you are somewhere on a line bearing 090T from the lighthouse, i.e., the LOP runs east-west through a point bearing 270T from the lighthouse). Advance this line 3 miles in the direction 000T (north). Plot the second LOP from the lighthouse along bearing 225T reciprocal (045T from your vessel). Where the advanced first LOP crosses the second LOP is your running fix. Label it with the time of the second bearing and mark it with a circle and R.
PP4A reef lies 0.5 nm to the west of Danger Buoy #5. You need to pass east of the reef. A lighthouse on the reef shore bears 340T when you are in safe water. What danger bearing do you establish and how do you use it?+
The danger is to the west. To stay east of the reef, you must keep the lighthouse bearing of NLT (not less than) 340T. As you approach from the south, if your bearing to the lighthouse drops below 340T (lighthouse moves to the right, bearing decreasing toward 300T), you are heading west of the clearing line and toward the reef. Maintain bearing of 340T or greater (bearing increasing toward 360T/000T) to remain in safe water. Plot this clearing line on the chart, label it NLT 340T, and monitor it continuously on your hand bearing compass.
PP5Your GPS shows XTE 0.3 nm R. Your desired track is 090T. What does this mean and what action do you take?+
XTE 0.3 nm R means you are 0.3 nautical miles to the right of your intended track — you have drifted to the south of the rhumb line. To return to track, alter course to port. How much you alter depends on how far you are from the waypoint and whether you want to return gradually or directly. A common practice is to steer 20-30 degrees to the left of your track bearing until XTE reduces to zero, then resume the track course. Your chartplotter's bearing-to-waypoint (BTW) line and course-to-steer (CTS) display will guide you back.
Frequently Asked Questions
What is the difference between a fix and an estimated position in coastal piloting?
A fix is a position established by two or more simultaneous LOPs (lines of position) from reliable sources such as visual bearings, ranges, or GPS. It is plotted with a circle. An estimated position (EP) is based on dead reckoning from the last known fix, adjusted for estimated current set and drift. It is plotted with a square. A DR position (dead reckoning) uses only course and speed with no current correction — plotted with a half-circle. The fix is the most accurate; the EP is more accurate than DR when current is factored in.
How do you draw a danger bearing on a chart?
A danger bearing is a bearing from a charted object (lighthouse, buoy, headland) that marks the safe limit of approach toward a hazard. Draw a line from the danger through the charted object. Label it NLT (not less than) or NMT (not more than) followed by the bearing. When your actual bearing to that object is on the safe side of the danger bearing, you are clear. For example, if rocks lie to the east of a lighthouse, you keep the lighthouse bearing NLT 270T so the rocks stay behind your clearing line.
What is ferry angle and how is it calculated?
Ferry angle is the angle you head into a current to maintain a desired track over the ground. It is also called the crab angle. To calculate it, you construct a current triangle: draw your intended track (course to make good), add the current vector (set and drift), then solve for the heading that closes the triangle. The sine of the ferry angle equals (drift divided by vessel speed) multiplied by the sine of the angle between the current and track. For exam problems, most solutions use a vector diagram or the formula: ferry angle = arcsin(drift/speed × sin(current angle from track)).
What does Rule 9 require in a narrow channel?
Rule 9 (Narrow Channels) requires vessels to keep as far to the starboard side of the channel as is safe and practicable. Vessels less than 20 meters or sailing vessels shall not impede the passage of a vessel that can only navigate safely within a narrow channel. Overtaking in a narrow channel requires the vessel being overtaken to take action to permit safe overtaking (Inland: exchange of whistle signals). A vessel shall not cross a narrow channel if crossing would impede a vessel that can only navigate within the channel.
How do you identify a light at night from the Light List?
First observe the light characteristic: is it fixed (F), flashing (Fl), occulting (Oc), isophase (Iso), quick (Q), or composite group flashing (Al)? Count the number of flashes per group and time the period (one complete cycle). For example, Fl(3) 15s means three flashes then darkness, repeating every 15 seconds. Match this against the Light List for your area. Also note the nominal range (nautical miles in clear weather) and color sectors if any. Sector lights show different colors depending on the bearing from which they are observed — white in the safe sector, red or green in danger sectors.
What is a running fix and when do you use it?
A running fix is used when you can only observe one charted object at a time. Take a bearing on the object, plot the LOP, then advance it along your course and speed to the time of the second bearing. Where the advanced LOP crosses the second LOP is your running fix position. The accuracy depends on how precisely you know your course and distance run between bearings. Running fixes are particularly useful when rounding a headland with only one reliable landmark in sight.
What is cross-track error (XTE) in GPS navigation?
Cross-track error (XTE) is the perpendicular distance your vessel has deviated from the intended rhumb line track between two GPS waypoints. It is displayed in nautical miles or tenths of miles, with L (left) or R (right) to indicate which side of the track you are on. To return to track, steer a course angled back toward the track line. Modern chartplotters also show bearing to waypoint (BTW) and course to steer (CTS) to automatically account for current and return you to the track line.
Quick Reference — Piloting Formulas
D in nm, S in knots, T in hours. To find S: S = D ÷ T. To find T: T = D ÷ S.
Simplified formula when current is perpendicular to track. For other angles, use the current triangle.
Compare echosounder reading to chart by subtracting tide height and adding your draft offset.
East is best (add), West is worst (subtract). Can Dead Men Vote Twice.
D in nm, H = light height in feet, h = eye height in feet. Geographic range of a light.
Scope ratio: use 5:1 in calm, 7:1 in moderate conditions, more in storms.
Master Coastal Piloting on the Practice Questions
1,628+ practice questions including detailed piloting scenarios, chart reading, and current triangle problems. Track your progress by topic. The exam does not curve — hit 80%+ before you schedule it.
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