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All 6 lessons in Longitude & Latitude

  1. 1. The Earth as a Sphere — Coordinates, Great Circles, and Small Circles

    Describe the Earth's latitude-longitude coordinate system and classify lines on the globe as great circles (equator, meridians) or small circles (other parallels).

  2. 2. Angular Distance Between Two Points on the Globe

    Find the angular distance θ between two points using one rule — same side subtract, opposite sides add — for both the latitude (meridian) and longitude (parallel) cases.

  3. 3. Distance Along a Meridian — The Great Circle Distance Formula

    Apply D = θ/360 × 2πR to find the distance between two points on the same meridian or on the equator, and the distance from any point to a pole.

  4. 4. The Radius of a Parallel and the Small Circle Distance Formula

    Derive r = R cosφ, find the circumference of any parallel, and apply D = θ/360 × 2πR cosφ to two points on the same parallel of latitude.

  5. 5. Reverse Problems — Finding an Unknown Longitude or Latitude from a Given Distance

    Rearrange the distance formulas to find an unknown θ or φ, then convert the angle to a longitude or latitude using the direction of travel.

  6. 6. Speed, Time, Nautical Miles, and Multi-Leg Globe Journeys

    Convert between kilometres and nautical miles, find journey times with T = D/S, and solve multi-leg journeys combining great and small circle calculations.

Unit code SSGM7