Marine & Navigation

COLREGs Encounter Classifier

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

Last validated: 2026-02-14

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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Input Pattern

Enter values in the left panel, keep units explicit, run the calculation, then copy or share the result. Invalid fields are highlighted immediately.

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.

How to use this tool

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

Worked Example

Auto-generated from the tool's current default or entered inputs.

Example Inputs

Own course deg: 90.0
Target course deg: 270.0
Relative bearing deg: 20.0
Encounter type: Crossing (vessel on starboard side)
Guidance: Give-way situation. Take early and substantial action to keep well clear.

Expected Outputs

Own course deg: 90
Target course deg: 270
Relative bearing deg: 20

Interpretation

Own course deg is 90.0. Use this as a decision input, not as a standalone conclusion.
Target course deg is 270.0. Use this as a decision input, not as a standalone conclusion.
Relative bearing deg is 20.0. Use this as a decision input, not as a standalone conclusion.
Cross-check the result against one alternate input set to validate sensitivity.

Scenario Compare (A vs B)

Use this to compare two input sets and quantify change in key outputs.

Scenario A

Own course deg

Target course deg

Relative bearing deg

Encounter type

Guidance

Scenario B

Own course deg

Target course deg

Relative bearing deg

Encounter type

Guidance

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Tailored guides for specific audiences, regions, and scenarios.

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Bridge training resources

Promote COLREGs training materials, simulator programs, and bridge procedure guides.

COLREGs Encounter Classifier

Input Pattern

Encounter Inputs

Classification

How to use this tool

Worked Example

Example Inputs

Expected Outputs

Interpretation

Scenario Compare (A vs B)

Scenario A

Scenario B

Explore more versions

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Bridge training resources