🔍 Key Concepts

• Circle of equal altitude definition in celestial navigation • Meaning of geographical position (GP) of a celestial body • Role of the observer’s position (assumed or DR) when plotting a sight

💭 Think About

• When you take a sextant altitude, what set of all possible observer positions would give you that same altitude? Where is the center of that set? • Which of the answer choices refers to a fixed point on Earth directly related to the celestial body, and which refer to positions related to the navigator? • Does the circle of equal altitude move with the ship or is it fixed to something else on the Earth at that instant?

✅ Before You Answer

• Be clear on the definition: GP of a body is the point on Earth directly under the celestial body (where it is at the zenith). • Distinguish between true physical points on Earth (like GP) and chosen/estimated points used for calculation (assumed position, DR position). • Ask yourself: the circle of equal altitude is constructed around what real point on Earth, not around a guessed or assumed location.