Non-Lateral Markers
Introduction to Non-Lateral Aids
While lateral markers (red and green) form the backbone of channel marking, there are many navigation situations that cannot be adequately addressed by simple "left side / right side" markers.
Non-lateral markers serve specific purposes unrelated to marking channel edges:
- Indicating safe water with navigable water all around
- Marking isolated dangers that can be passed on either side
- Designating special areas or features
- Providing regulatory information
These aids use distinctive color schemes and shapes that are standardized worldwide under both IALA Region A and Region B (unlike lateral markers, which reverse colors between regions).
Safe Water Markers (Mid-Channel Markers)
Safe water markers indicate that navigable water exists on all sides of the marker. They are typically used to mark:
- The entrance to a channel from open water
- The center (mid-channel) of a wide fairway
- The seaward end of a channel
- A safe approach point offshore
Color: Red and white vertical stripes
The stripes are equally sized and run vertically (up and down) on the marker.
Shape (if buoy): Spherical (ball-shaped) or pillar with spherical topmark
A spherical buoy is distinctively round, like a beach ball floating in the water. Pillar buoys with spherical topmarks have a round ball mounted on top of a cylindrical body.
Dayboard (if beacon): Octagon (8-sided) with red and white vertical stripes
The octagonal shape is unique to safe water markers.
Light (if lighted): White
The light is white (not red or green). The characteristic is typically:
- Morse Code "A" (short-long: • -)
- Isophase (equal periods of light and dark)
- Occulting (light on longer than off)
- Long Flash (flash duration 2 seconds or more)
Sound signal (if equipped): Single tone (one pitch)
Often a bell or horn with a single note.
Meaning: "Safe water all around me"
You may pass this marker on either side, though often local practice or chart guidance indicates a preferred side in channels with traffic.
Common usage:
Fairway Buoys: Mark the entrance to a major channel or harbor from offshore. Named with "F" or abbreviated "Fairway."
Example: A red and white vertically striped spherical buoy with white Morse "A" light marks the approach to San Francisco Bay. Vessels from the Pacific Ocean pass close to this marker before entering the channel marked by lateral aids.
Mid-Channel Buoys: Mark the center of a wide channel or river, especially where traffic separation is needed.
Practical navigation: Safe water markers are often your first visual reference when approaching a harbor from sea. Look for the distinctive red/white stripes and white Morse "A" light as a landfall reference.
Isolated Danger Markers
Isolated danger markers indicate a specific, isolated hazard with navigable water all around it. The hazard might be:
- A submerged rock or reef
- A wreck
- A small shoal
- A submerged obstruction (old pier pilings, etc.)
Color: Black with one or more horizontal red bands
The red bands are horizontal (running around the marker), distinguishing them from the vertical stripes of safe water markers.
Topmark: Two black spheres (balls) in vertical line
This is the distinctive and unmistakable identifier. The two balls are stacked vertically.
Light (if lighted): White
The characteristic is:
- Group Flashing (2) - written as Fl (2) or Gp Fl (2)
- Two flashes in quick succession, then darkness, then repeat
The "two flashes" correspond to the "two balls" of the topmark, providing a memorable association.
Sound signal (if equipped): Two-tone (alternating pitches)
A bell or horn alternating between two different notes, corresponding to the "two" theme.
Meaning: "Danger here, but navigable water around me"
You may pass this marker on either side, but you should pass well clear. The isolated danger is directly at or near the marker's position.
Practical navigation:
Identify the hazard on the chart: Before approaching, check your chart to see what the marker is warning about. The chart will show the wreck, rock, or shoal location and depth.
Determine adequate clearance: Based on your vessel's draft, decide how far to stay away. A depth of 10 feet over a rock requires wide clearance for a vessel drawing 6 feet.
Pass on the side with more room: If current or other traffic considerations favor one side, pass on that side, but always give wide berth.
Common hazards marked:
- Wrecks in shipping lanes
- Isolated rocks in otherwise deep water
- Man-made hazards (old platform remains)
- Small shoals in large bays
Safety note: Particularly in strong currents or tides, isolated danger markers may be positioned offset from the hazard (not directly over it) to prevent the marker itself from striking the danger or to account for swinging room. Always consult the chart for the exact hazard position.
Special Markers (Yellow Markers)
Special markers indicate special areas or features that don't fit into other ATON categories. They do NOT indicate navigable channel limits.
Color: Yellow
All yellow markers are special markers. Yellow is not used for any other purpose in the ATON system.
Shape: Can (if floating), or varies for fixed beacons
Can-shaped buoys are most common, but shape is not standardized for special markers.
Light (if lighted): Yellow
Characteristic: Usually Fixed (F) or Flashing (Fl)
Yellow lights are distinctive and easily recognized.
Meaning: "Special purpose or area"
The specific meaning depends on context and must be determined from the chart or local Notice to Mariners.
Common uses:
Traffic Separation Schemes: Mark the boundaries of shipping lanes and separation zones. Recreational vessels should cross these perpendicularly and avoid lingering in them.
Anchorage Areas: Mark the limits of designated anchorages.
Dredging/Survey Operations: Mark areas of dredging, survey work, or underwater construction.
Ocean Disposal Sites: Mark areas designated for dredging spoil disposal.
Military Exercise Areas: Mark areas restricted for naval exercises or weapons testing.
Fish Net Areas: Mark areas with deployed fishing nets or fish traps.
Spoil Areas: Mark areas where material dredged from channels has been dumped (often shallow).
Pipelines and Cables: Mark the route of underwater pipelines or cables where anchoring is prohibited.
Seaplane Landing Areas: Mark areas designated for seaplane operations.
Practical navigation:
Consult the chart: Special markers require chart reference to determine their specific purpose. The chart will have a label (e.g., "Fish Haven," "Pipeline Area," "Dump Site").
Check Notices to Mariners: For temporary special markers, consult Local Notices to Mariners for information on restrictions or hazards.
Respect restrictions: Many special marker areas have legal restrictions (no anchoring, no fishing, speed limits). Violating these can result in significant penalties.
Regulatory compliance: Some special marker areas are established under federal or state law with enforceable penalties for violations. Examples:
- Anchoring over pipelines: Heavy fines and liability for damage
- Entering military exercise areas: Federal penalties and safety hazards
- Violating traffic separation schemes: USCG enforcement action
Information and Regulatory Markers
These markers provide information or indicate regulatory restrictions. They are often found in state waters and may not conform to federal ATON standards in all details, but they provide critical safety and legal information.
Color: Varies by type, but commonly white with orange symbols or bands
Shape: Varies by type
These markers are covered in full detail in Lesson 5 (State Marking System), but key types include:
Danger Markers: Orange diamond shape indicating hazard
Keep Out Markers: Orange crossed diamond indicating restricted area
Control Markers: Orange circle indicating regulated activity (speed limit, no wake, etc.)
Information Markers: Orange square or rectangle with information
Comparison Summary Table
| Marker Type | Colors | Shape/Topmark | Light | Meaning | |-------------|--------|---------------|-------|---------| | Safe Water | Red & White Vertical Stripes | Sphere / Octagon | White (Morse A, Iso, Occ) | Navigable all around | | Isolated Danger | Black with Red Horizontal Bands | Two Black Balls Vertical | White Gp Fl (2) | Danger here, pass either side | | Special | Yellow | Can / Varies | Yellow (Fixed or Fl) | Special area/purpose | | Regulatory | White with Orange | Varies by type | Usually none | Regulatory/information |
Summary
Non-lateral markers serve purposes beyond channel edge marking. Safe water markers (red/white vertical stripes, sphere shape, white Morse A light) indicate navigable water on all sides and typically mark channel entrances or mid-channel positions.
Isolated danger markers (black with red horizontal bands, two black balls topmark, white group flashing 2 light) mark specific hazards surrounded by navigable water-pass well clear on either side.
Special markers (yellow, can shape, yellow light) mark special areas or features-consult chart for specific meaning. Regulatory markers (white with orange shapes) provide legal restrictions and information.
All non-lateral markers are consistent between IALA Region A and B, making them internationally standardized.
Key Takeaways
- Non-lateral markers do NOT indicate channel edges-they serve other purposes
- Safe water markers: red/white vertical stripes = navigable all around (fairway, mid-channel)
- White Morse "A" light is distinctive identifier for safe water markers
- Isolated danger markers: black with red horizontal bands, two balls topmark = pass well clear
- White group flashing (2) light on isolated danger markers-two flashes = two balls
- Special markers: yellow color = special area or purpose (must check chart)
- Special marker areas often have legal restrictions-violations can result in penalties
- Safe water and isolated danger markers are the same worldwide (IALA A & B)
- Always consult chart to understand non-lateral marker specific meaning and local regulations