Map Scale

Maps are a graphical representation of the world or a section of the world.  As a representation of the world, maps are compressed versions of the real world meaning that a large piece of land is recreated onto a smaller piece of paper or digital file.  The relationship between the real world size of a geographic feature and its representative feature on a map is known as scale.

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Scale is often represented as a ratio between the real world size and the size in units on the map.

How Scale is Shown on a Map

There are three main ways that scale is indicated on a map: graphic (or bar), verbal, and representative fraction (RF).

Bar scales show scale using a graphic format.  The actual length of the bar scale shows what that length represents in real world units.  In the example below, the bar scale shows the distance on the map that represents ten kilometers or a little under six miles.

Showing scale using a graphic scale.

Showing scale using a graphic scale.

Scale can also be represented verbally or in text format. For example the verbal scale, 1″ = 100′ means that one inch measured the the map represented 100 feet on the ground.  This type of scale representation visually looks very similar to representative fraction (RF).  However, representative fraction avoids the use of units in detailing the scale of a map.  For example, scale that has a RF of 1:100 means that every one unit on the map equals one hundred of the same units on the ground.  In comparable terms a RF scale of 1:1,200 is the same scale as a verbal scale of 1″ = 100′.

Large Scale and Small Scale Maps

Maps can be described by how varied the scale is.  Maps that show a large geographic area in comparison to the relative size of the map are known as small scale maps.  The small scale refers to how small the fraction is.  A map showing the entire world would be considered a small scale map whereas a map showing a neighborhood would be considered a large scale map.

Small scale maps tend to show a larger geographic area and less detailed and large scale maps show a smaller geographic area with greater detail.   In the example below, the small scale map of the Chicago area shows only major transportation routes, and rivers.  In the large scale map, far more detail is available such as all the streets, building footprints, street flow direction, and increased labeling of more features.

Small scale map showing Chicago (upper map) and a large scale map showing a neighborhood in Chicago (lower map).

Small scale map showing Chicago (upper map) and a large scale map showing a neighborhood in Chicago (lower map).

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