Tool for calculating lengths according to drawing scales / maps scales / plans scales from the length as it is drawn or as actually measured.
Map Scale - dCode
Tag(s) : Arithmetics
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A scale of a map (or a diagram or a drawing) is a ratio, a fraction between 2 numbers, the first represents the value measured on the map, the second its correspondence with the actual value of the element.
Example: A scale 1:100 is read 1 to 100 or 1 hundredth scale and means that 1 unit on the map corresponds to 100 units in reality. It can be 1cm (which will be 100cm) or 1km (which will be 100km). The plan is a shrinking 100 times smaller than reality.
Example: A scape 2:1 reads 2 to 1 and means that 2 units on the plane correspond to 1 in reality. This means that the plane is a magnification 2 times, a zoom x2 of reality.
Measure an element on a drawing or a map and note its value $ a $ (any unit). Then measure this same element in reality and note its value $ b $ (same unit as $ a $). The scale is the result of dividing $ a / b $.
It is common to modify the writing of the fraction by putting it in the form of an irreducible fraction or to use the numerator $ 1 $ for reality-narrowing drawings, or use the denominator $ 1 $ for reality-enlarging drawings.
If a map is scaled, its measurements are proportional to reality, the coefficient of proportionality is the inverse of the value of the scale.
Example: 2cm on a scale drawing 1:10 (ie 1/10 whose inverse is '10/1 ') corresponds to 2*(10/1)=20cm in reality.
Conversely, starting from a real length, its multiplication by the scale makes it possible to calculate its length on the map.
Example: 20cm actually represent 2cm on a diagram with scale 1:10 because 20*(1/10)=2cm