Lessons · Teaching · reading a map: scale, key, grid and direction
Four things to read before you read the map
Every map carries a title, a key explaining its symbols, a scale relating map distance to real distance, and a direction indicator. Reading those four first is what turns a picture into information, and a map that omits one of them cannot be used properly.
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In beta. This lesson was written for Hone and has not yet been checked by a state certification officer. Practice material, not professional advice. What that means.
What it is for
A pupil who measures a distance without checking the scale has produced a number that means nothing, and it is the same error as reading a pictograph without its key. The habit transfers: check what the representation claims before trusting what it shows.
How to think about it
Read title, key, scale and direction, in that order, before looking at the content. Use the scale by measuring on the map and multiplying. On a grid, give the coordinates in the order the map states, and remember that a globe and a flat map cannot both be right about shape and area.
Worked example
Title says what the map is of, and a map can only answer questions about thatA rainfall map cannot tell you where the roads are.
The key explains every symbol, and symbols differ from map to mapNothing is standard except by convention, so the key is not optional.
The scale converts: 1 cm on the map standing for 5 km means 4 cm is 20 kmMeasure, then multiply. Skipping the scale produces a meaningless number.
Every flat map distorts something, because a sphere cannot be flattened without stretchingWhich is why map areas and shapes disagree between projections.
Your turn
Name the part of a map that converts a measured distance into a real one.
Map distance is converted to real distance by the
Solve one, graded on the server
The trap
Believing a familiar world map shows true sizes. Every flat projection distorts area, shape, distance or direction, and the common ones exaggerate land far from the equator.