🔍 Key Concepts

• Geodetic latitude vs. geographic latitude and how it’s measured on the Earth’s surface • How the length of one minute of latitude (and thus one degree) relates to a nautical mile • The effect of the Earth not being a perfect sphere (it’s slightly flattened at the poles)

💭 Think About

• Think about where on Earth the assumption of 60 nautical miles per degree of latitude would match reality best if the Earth were very close to a perfect sphere. • Consider whether the length of a degree of latitude changes more near the equator, in mid‑latitudes, or near the poles on a slightly flattened (ellipsoidal) Earth. • Ask yourself: if 60 NM/degree is only an approximation, would it be most accurate in the middle, at one end, or everywhere?

✅ Before You Answer

• Recall that 1 nautical mile is defined based on 1 minute of arc of latitude on a reference Earth model, not the exact measured value everywhere. • Consider whether the Earth’s polar flattening makes degrees of latitude slightly longer or shorter toward the poles. • Decide if it is reasonable that the same exact distance (60 NM) would apply at all latitudes, or whether there is a latitude band where the approximation is closest.