🔍 Key Concepts

• Running fix concept: advancing an earlier Line of Position (LOP) along the DR track to a later time • How radar range arcs represent all possible positions at a fixed distance from an object • Difference between moving the ship’s position vs. changing the measured range

💭 Think About

• When you have an arc from a radar range at an earlier time and you later get a second LOP, what actually moves over time: the object, the ship, or the range measurement? • Should the shape (curved arc vs. straight line) of the LOP change when you advance it, or should it keep the same geometric form? • In a running fix, how is the vessel’s DR track used to relate the earlier observation to the later time?

✅ Before You Answer

• Make sure you keep the same radius that corresponds to the original radar range unless there is a new measurement • Confirm that what you are ‘advancing’ in time is the vessel’s DR position relative to the fixed object, not the physical object itself • Verify that the method preserves the fact that a radar range LOP is an arc of a circle around a fixed point, not a straight line