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MASS Time-to-Collision

Time-to-collision between own ship and target based on relative-position vector. Used inside autonomous collision-avoidance algorithms.

MASSAutonomous
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Formula, assumptions, and limits

TTC=RangeClosing rateTTC = \frac{\text{Range}}{\text{Closing rate}}
SymbolMeaningUnit
RangeRangeCurrent rangenm
ClosingrateClosing rateRate of approachkn
TTCTTCTime to collisionmin

Source: COLREGS Rules 7–8

In short

Time-to-collision between own ship and target based on relative-position vector.

Learn the theory Autonomous Ships (MASS): The Regulatory State