← Spark & Whetstone · The Arithmetic of the Chessboard
Artists have scaled drawings up with a grid for centuries: copy one small square at a time into a bigger square, and the proportions take care of themselves. Set the sizes, print the blank grid, and draw.
Every length in the copy is the same multiple of the matching length in the picture: that multiple is the scale. The grid makes it visible. A square that is 2.5 cm on the picture and 7.5 cm on the copy is a scale of 3, so every line inside it is three times as long. Areas grow by the square of the scale: a copy three times as wide covers nine times the paper.
Letter the columns and number the rows on both grids, as on a chessboard, and you can always find your place again.
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