Safety depth, in the context of ECDIS (Electronic Chart Display and Information System) and ECS (Electronic Chart System), is a user-defined depth setting that dictates how soundings (displayed depth measurements) are visually represented on the chart.
Here's a breakdown:
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Purpose: To highlight areas of potentially shallow water and provide a visual warning to the navigator.
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Functionality: When a navigator sets a specific safety depth value, the ECDIS/ECS will typically display soundings in different colors or patterns based on their relationship to this safety depth.
- Soundings Deeper Than the Safety Depth: Usually displayed in a default color, often gray, indicating relatively safe water.
- Soundings Equal to or Shallower Than the Safety Depth: Typically displayed in a different, more prominent color, often black, highlighting potentially hazardous areas. This is the key element described in the provided reference.
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User-Defined: The navigator chooses the safety depth based on factors such as the vessel's draft, squat (the decrease in under-keel clearance when a vessel is moving), and desired safety margin.
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Example: If a vessel has a draft of 10 meters and the navigator wants a 2-meter safety margin, they might set the safety depth to 12 meters. Any sounding of 12 meters or less would then be highlighted on the ECDIS/ECS display.
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Importance: The safety depth setting is crucial for safe navigation, as it provides a quick and easy way to identify potentially hazardous areas and avoid grounding.
In essence, safety depth is a crucial tool in ECDIS/ECS that allows navigators to visually prioritize depth information relative to their vessel's characteristics, aiding in safe navigation and grounding avoidance.
