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Geography · Grade 9

Coordinates, Scale and Projections

A quantitative return to the geographer's basic tools. Learners link the number of decimal places in a coordinate to distance on the ground, calculate great-circle distances with the spherical law of cosines and compare them with constant-bearing routes, solve time-zone and date-line problems, and measure projection distortion with scale factors and Tissot's indicatrix before choosing projections for real tasks.

  • 4 lessons
  • About 115 minutes
  • Quantitative map skills check: 10 questions
  • Ways to answer: choose an answer, pin a map, match pairs, type a number, put in order and true or false
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What learners will discover

  • Relate coordinate precision to ground distance, allowing for the shrinking length of a degree of longitude, and choose a suitable precision for a task.
  • Calculate great-circle distances and compare them with rhumb-line (constant-bearing) routes.
  • Solve time problems using longitude, UTC offsets and the International Date Line.
  • Quantify projection distortion with scale factors and Tissot's indicatrix, and justify a projection for a purpose.

Lessons

  1. How precise is a coordinate? 6 steps4 practiceabout 28 min
  2. Great-circle distance by calculation 6 steps4 practiceabout 30 min
  3. Longitude, time and the date line 6 steps4 practiceabout 27 min
  4. Measuring distortion 6 steps3 practiceabout 30 min
  5. Quantitative map skills check 10 questions at the end

Keep exploring

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Guide for grown-ups