Lesson 39
Maps and Real-World Directions
Extends compass directions to maps: how a compass works, what a map keeps and drops, and why every flat map of a round Earth distorts something, size, shape, or both. You'll compare the Mercator, Gall-Peters, and Robinson projections against the globe with your child.

Workbook Pages

L39 Maps and Real-World Directions by Selene

Key Ideas

  • Left and right depend on which way your body is facing, so they cannot give directions another person
  • can reliably follow.
  • North, East, South, and West are fixed and the same for everyone. You can find them using the
  • sunrise or a compass.
  • A map is a bird's-eye drawing that keeps direction and relative position and drops everything else. It
  • needs a compass rose to be read correctly.
  • A round Earth cannot flatten into a map without distortion. Mercator sacrifices size, Gall-Peters
  • sacrifices shape, and Robinson compromises on both a little.
  • Because of Mercator-style stretching near the poles, Africa looks small on most classroom maps. It is
  • actually about 14 times the size of Greenland.

Vocabulary
  • Cardinal directions: North, East, South, and West: the four fixed directions that are the same for everyone on Earth, no matter which way they are facing.
  • Compass: A tool with a free-spinning magnetized needle that lines up with the Earth's magnetic field and always points North.
  • Compass rose: The N, E, S, W symbol printed on a map showing how the map lines up with the real-world directions.
  • Map: A flat, shrunk-down drawing of a real place, seen as if from directly above, that keeps direction and position and drops everything else.
  • Projection: A method for turning the round Earth into a flat map. Every projection distorts something, either the size or the shape of landmasses.
  • Mercator projection: A map projection that keeps direction and shape accurate, useful for sailors, but badly stretches size near the poles.
  • Gall-Peters projection: A map projection that keeps every landmass at its true relative area, at the cost of warping shapes.

Talk It Over 

1. A ship's captain in 1500 needed accurate direction more than accurate size. A modern hiking app needs the opposite. Which map projection would each prefer, and why?

2. If you shrank a basketball down to the size of a coin without cutting it, could you flatten its surface without any wrinkles or stretching? What does that tell you about every world map ever made?

3. Africa, Europe, and North America are drawn close to their true sizes on a Gall-Peters map, but their shapes look squashed. Why might a mapmaker accept that trade-off?

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