Navigation Basics for Pacific Northwest Boaters

Why Navigation Matters More Than You Think

Modern chartplotters and GPS have made navigation vastly easier than it was 30 years ago — and they’ve also created a generation of boaters who don’t know what to do when the electronics fail. In the PNW, with its fog, complex currents, and abundant shipping traffic, understanding the basics of marine navigation is a genuine safety skill.

This guide covers the fundamentals: reading charts, understanding aids to navigation, planning a route, and knowing the rules of the road.

Nautical Charts: The Language of the Sea

A nautical chart is not just a map — it’s a specialized document that shows water depths, bottom composition, hazards, aids to navigation, restricted areas, and more. Learning to read one unlocks the sea.

Chart datum: All depths on NOAA charts are referenced to MLLW (Mean Lower Low Water). As we cover in the Tides guide, actual depth is charted depth plus current tide height.

Depth contours: Like topographic contour lines on land, depth contours show where the bottom rises. In the PNW, a 6-fathom (36-foot) contour line is a useful safety boundary for larger boats.

Bottom composition abbreviations:

• M = mud (good holding for anchors)
• S = sand (good holding)
• Rky = rocky (poor holding; anchor nearby, not on top)
• K = kelp (soft substrate, often good holding, but kelp can foul propellers)

Hazard symbols:

• A circle with an X = rock that dries (dangerous at low tide)
• A cross symbol = submerged rock
• The notation “8f” = 8 fathoms (48 feet) at chart datum

Scale: Pacific Northwest charts come in different scales. Large-scale charts (1:10,000 to 1:40,000) show individual harbors and passages in detail. Small-scale charts (1:200,000+) show large areas with less detail. Use the appropriate scale for where you are.

GPS and Chartplotters

Modern GPS chartplotters integrate GPS position with electronic charts (NOAA Electronic Navigational Charts, or ENCs) to show your position in real time on a digital chart. They are powerful and reliable — but not infallible.

Best practices:

• Always carry a backup — a tablet with offline charts or a handheld GPS chartplotter
• Verify GPS position against visual landmarks regularly
• Do not sail at night in unfamiliar waters relying solely on GPS without a trained watch
• Check the chart datum matches the GPS datum (both should be WGS84 in modern equipment)

Useful features:

• COG (Course Over Ground) — where you’re actually going, accounting for current and leeway
• SOG (Speed Over Ground) — actual speed over the seabed
• WPT (Waypoint) — a saved GPS position; waypoints can be chained into a route
• XTE (Cross Track Error) — how far off your planned track you’ve drifted

Aids to Navigation (AtoN)

The US uses the IALA-B buoyage system (used in the Americas; different from IALA-A used in Europe/Canada/Australia — know which you’re in).

IALA-B rules:

• Red buoys (even numbers) — keep to your right when entering harbor (returning from sea). “Red Right Returning.”
• Green buoys (odd numbers) — keep to your left when entering harbor.
• Red-and-white vertically striped buoys — safe water (fairway buoy); you can pass on either side; often at harbor entrances.
• Yellow buoys — special purpose (cables, restricted areas, fish farms).

Buoy shapes:

• Nun buoy — pointed top; always red (in IALA-B)
• Can buoy — flat top; always green
• Spar buoy — a cylindrical post; can be red or green
• Lighted buoy — any buoy with a light; red lights on red buoys, green lights on green

Light characteristics: On charts and buoy lists, lights are described by their characteristic:

• Fl = flashing (a single flash at regular intervals)
• Fl(2) = group flashing (two flashes in a group)
• Iso = isophase (equal on and off)
• Oc = occulting (light on longer than off)
• Q = quick (flashing 50–79 times per minute)
• Period is given in seconds: “Fl R 4s” = flashing red, every 4 seconds

Rules of the Road (COLREGs)

The International Regulations for Preventing Collisions at Sea (COLREGs) — called the “Rules of the Road” — govern who gives way to whom on the water. Every skipper must know the basics.

Sailing vs. power: A vessel under sail has right-of-way over a vessel under power — except when the sailing vessel overtakes the power vessel, or when the power vessel is constrained in its ability to maneuver (a ferry in a channel, a ship in a shipping lane).

Stand-on vs. give-way: The vessel with right-of-way is the “stand-on” vessel — it maintains course and speed. The “give-way” vessel must take action to avoid collision (turn, slow down, or stop).

Between two sailing boats:

• Port tack (wind from port) gives way to starboard tack (wind from starboard)
• If on same tack, windward boat gives way to leeward boat

Overtaking: Any vessel overtaking another must give way to the vessel being overtaken, regardless of whether it’s a sailboat or power vessel.

Head-on (power): Two power vessels meeting head-on each turn to starboard (right), passing port-to-port.

Crossing (power): The vessel with the other’s bow to its starboard (on the right) is the stand-on vessel.

Narrow channels: Stay to the starboard side of a narrow channel. Vessels that can only safely navigate in the channel (large ships) have right-of-way over small recreational vessels that can safely leave the channel.

Sound signals:

• 1 short blast = I am turning to starboard
• 2 short blasts = I am turning to port
• 3 short blasts = I am going astern (reverse)
• 5 short blasts = danger signal (warning of collision)

Route Planning

A properly planned route makes navigation easier and reduces risk. Here’s the process:

1. Select your start and end points. Mark them as waypoints.
2. Plot the route on the chart. Connect waypoints with straight lines.
3. Check each leg for hazards: shoals, rocks, traffic separation schemes, restricted areas.
4. Adjust waypoints to clear hazards with a safe margin.
5. Note the distance and bearing of each leg.
6. Calculate timing using your expected speed, factoring in currents (favorable = faster, opposing = slower).
7. Check tide predictions for any tidal passages on your route.
8. Identify bail-out points — anchorages or ports where you can shelter if conditions deteriorate.

VHF Radio Basics

A marine VHF radio is required equipment. Know how to use it.

Channel 16 — The international calling and distress channel. You must monitor Channel 16 at all times when underway (unless in a sheltered anchorage). All vessels and the Coast Guard monitor it.

Channel 22A — US Coast Guard working channel. After hailing the Coast Guard on 16, they’ll direct you to 22A.

Channel 14 — Seattle Vessel Traffic Service. Monitor when in the Main Basin.

Channel 9 — Recreational boating calling channel (alternate to 16 for non-emergency calls).

Calling procedure: Transmit: “[Station name], this is [your vessel name], on one six.” Listen for reply. If none after 2 minutes, try again. After contact, agree to a working channel and switch there.

MAYDAY procedure (life-threatening emergency): On Channel 16: “MAYDAY MAYDAY MAYDAY. This is [vessel name, repeated 3 times]. Position: [latitude/longitude or description]. [Nature of distress]. [Number of people aboard]. [Any other relevant information]. MAYDAY [vessel name].”

Compass and Magnetic Variation

The PNW lies in an area with significant magnetic variation — the difference between true north and magnetic north. In the Seattle area, magnetic variation is approximately 15° East (varies slightly by location).

On your chart compass rose, variation is noted. On NOAA charts, it’s updated annually. Your electronic chartplotter handles this automatically, but if using a magnetic compass, you need to apply the correction to convert between true and magnetic bearings.

The memory aid: “Variation East, Magnetic Least” — if variation is East, the magnetic bearing is less than the true bearing.