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Each division or unit of measure is the same and used on most small state and country maps. A regular ruler is a linear scale and directly relates to a fixed linear scale shown on the map such as 1" = 200 miles etc. in which case 4" would equal 400 miles. In a non linear scale, the 4" would have a different value
A FLAT world map uses a scale called the MERCATOR Projection and the scale varies depending on what latitude is being measured. In other words, 1" does not have the same value at different latitudes.
Another common scale is the logarithmic scale used in science where each unit of the scale is a factor of 10 of the previous. The first unit is 1-10, the second 10-100, the third is 100-1000, etc. This is the scale used on the old "slide rule" calculator and not familiar to most people since the introduction of the digital calculator although it is still commonly seen as one of the axis of a graph.
