ECDIS Parameters: Safety Contour, Safety Depth, Shallow Contour, and Deep Water Contour

The Electronic Chart Display and Information System (ECDIS) plays a pivotal role in modern navigation, providing mariners with crucial information to ensure safe voyages. Among the many parameters available, the safety contour, safety depth, shallow contour, and deep water contour are essential to prevent groundings and improve voyage planning. Understanding and correctly configuring these settings are vital for maintaining safety at sea.

This guide will break down each of these ECDIS parameters, explain their significance, and offer step-by-step instructions to set them properly.

Why Are ECDIS Safety Parameters Important?

The ECDIS helps mariners visualize safety-critical data by employing contour lines and alert systems to identify potential hazards. By properly setting parameters like the safety contour, safety depth, shallow contour, and deep water contour, captains and officers can:

  • Prevent groundings by marking unsafe areas clearly.
  • Detect isolated dangers and shallow water zones.
  • Enhance situational awareness, particularly in unfamiliar or high-risk waters.
  • Comply with the International Maritime Organization (IMO) and company standards for operational safety.

Without these settings configured correctly, the potential for navigational errors increases dramatically, posing risks to the vessel, crew, cargo, and environment.

What Is a Safety Contour in ECDIS?

The safety contour is perhaps the most critical ECDIS parameter. It acts as a visual boundary line that divides safe and unsafe waters based on the vessel’s draft and other operating conditions. Its primary purposes are:

  • Highlighting unsafe water areas on the electronic chart.
  • Detecting isolated dangers.
  • Triggering anti-grounding alarms when the vessel crosses into unsafe waters.

This contour is prominently displayed on the ECDIS using a bold line, making it easy for navigators to identify potential hazards as they plan and execute their voyage.

How Is the Safety Contour Calculated?

The safety contour is determined using this formula:

Safety Contour = Maximum Draft (static) + UKC (Company Policy) + Squat (Maximum) – Height of Tide

Where:

  • Maximum Draft (static): The deepest part of the vessel below the waterline in still water.
  • UKC (Under Keel Clearance): A safety margin set by company policy to ensure the vessel doesn’t touch the seabed.
  • Squat (Maximum): The additional sinkage of the vessel due to its speed in shallow water.
  • Height of Tide: The water level above chart datum (adjusted as per tidal changes).

Once the safety contour is calculated, the ECDIS will generate an alarm if the vessel approaches or crosses this boundary, minimizing the risk of running aground.

Pro Tip: When the calculated safety contour doesn’t match one of the predefined chart contours, the ECDIS will display the next deeper contour by default.

What Is Safety Depth in ECDIS?

The safety depth works in conjunction with the safety contour but serves a slightly different purpose. While the safety contour focuses on unsafe waters, the safety depth highlights specific depth soundings (numbers on the chart) that are considered unsafe.

How Is Safety Depth Set?

The safety depth is calculated using this formula:

Safety Depth = Maximum Draft (static) + UKC (Company Policy) + Squat (Maximum) – Height of Tide

For example:

  • If a vessel has a static draft of 10 meters, a UKC of 1 meter, a maximum squat of 1.5 meters, and the tide adds 2 meters:

Safety Depth = 10 + 1 + 1.5 – 2 = 10.5 meters.

Depth soundings equal to or shallower than this value will be displayed in bold on the ECDIS, making them easy to identify at a glance.

Important: While setting safety depth, ensure it aligns with the calculated safety contour to maintain consistency in safe navigation planning.

What Is a Shallow Contour in ECDIS?

The shallow contour marks the depth level below which a vessel can run aground. This parameter is directly tied to the vessel’s static draft and represents the absolute minimum safe depth for navigation.

How Is the Shallow Contour Calculated?

The shallow contour equals the vessel’s maximum static draft.

For example:

  • If a vessel’s draft is 10 meters, the shallow contour should also be set at 10 meters.

The ECDIS fills areas shallower than the shallow contour with a specific color (typically blue), visually warning navigators of potential grounding zones.

Key Tip: Always ensure the shallow contour reflects the vessel’s actual draft to prevent accidental encroachment into hazardous waters.

What Is the Deep Water Contour in ECDIS?

The deep water contour represents the limit of areas where shallow water effects, such as squat, no longer apply. Beyond this contour, vessels are considered to be navigating in deep water where these effects are negligible.

How Is the Deep Water Contour Determined?

The deep water contour is typically set at:

  • Twice the vessel’s draft in shallow water areas.
  • Four times the vessel’s draft in deep water areas.

For example:

  • If a vessel’s draft is 10 meters, the deep water contour may be set at 20 meters (shallow water) or 40 meters (deep water).

By clearly marking this contour, navigators gain an additional layer of situational awareness. Areas between the safety contour and the deep water contour are often displayed in lighter shades of blue to indicate caution.

Navigation Tip: Consult tide tables and local navigation charts to adjust the deep water contour settings for specific regions.

Best Practices for Setting ECDIS Safety Parameters

  1. Regularly Update Data: Ensure the electronic chart data, including tidal information, is up-to-date before calculating safety parameters.
  2. Follow Company Policy: Always align settings with the vessel operator’s safety manual or policy guidelines.
  3. Cross-Check with Other Systems: Validate ECDIS settings against the vessel’s echo sounder, radar, or other navigation tools for redundancy.
  4. Adjust for Local Conditions: Account for regional factors like tides, squat, and weather when recalculating safety margins.
  5. Train Your Team: Conduct regular ECDIS training and drills with your crew to ensure everyone understands the significance of these parameters.

By adhering to these practices, you can maximize the safety benefits ECDIS provides while minimizing the risk of navigational errors.

Avoid Groundings by Mastering ECDIS Safety Settings

By correctly configuring the safety contour, safety depth, shallow contour, and deep water contour, mariners can significantly reduce the risk of running aground, ensure compliance with regulations, and improve overall operational efficiency. These ECDIS parameters serve as vital tools for enhancing situational awareness and maintaining safe navigation.

Are you fully confident in your ECDIS settings? Take time today to review and adjust them based on your vessel’s draft, environmental conditions, and company guidelines. Safe navigation begins with smart preparation.