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Marine & Navigation Marine navigation

COLREGs Encounter Classifier

Classify head-on, crossing, or overtaking geometry from bearing/course data.

Marine & Navigation

COLREGs Encounter Classifier provides quick geometric classification of vessel encounters as head-on, crossing, overtaking, or uncertain from course and relative-bearing inputs. It is useful for bridge-team drills and scenario discussions when practicing collision-avoidance recognition. Output guidance is advisory and intentionally conservative. Use it as a training aid only and apply full COLREGs judgment, lookout, and local rules in live navigation.

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Marine navigation workflow links

Use this calculator as one part of a broader passage-planning workflow. The Marine Navigation Calculators toolkit explains how CPA/TCPA, UKC, tide windows, route distance, set and drift, fuel range, and manoeuvring checks fit together. You can also browse the full Marine & Navigation category.

Input guidance

Enter the vessel, route, tide, current, or clearance assumptions exactly as labelled, then verify the result against official data and onboard judgment.

How to use this tool

  1. Enter own course, target course, and target relative bearing from your bow.
  2. Run classification to get encounter type and advisory guidance text.
  3. Use output for training/debriefing and verify decisions with full COLREGs context.

Encounter Inputs

Classification

Encounter type: Crossing (vessel on starboard side)

Give-way situation. Take early and substantial action to keep well clear.

Operational note: This is an educational aid and does not replace proper lookout or full COLREGs application.

Formula or method

How to interpret the result

Assumptions

Review note and limitations

Related tools and workflows

Related marine tools help connect the calculation with route planning, clearance, drift, tide, encounter, or fuel checks. Start with CPA/TCPA Risk Calculator, Under Keel Clearance Calculator, and Tide Window Planner when you need a quick follow-up check.