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Guide to Map Scale


Background

This guide has been prepared to help users of the Map Collection to understand the concept of scale in cartography. Scale is defined as the ratio of the distance on a map to the corresponding distance on the surface the map represents.

Three forms of Scale:

Verbal Scale:

1 inch equals 16 miles

This example tells us that 1 inch on the map represents 16 miles on the surface of the Earth. This is the easiest scale to understand because it generally uses familiar units.

Graphic or Bar Scale

The Bar Scale is particularly important when enlarging or reducing maps by photocopy techniques because it changes with the map. If the Bar Scale is included in the photocopy, you will have an indication of the new scale.

Representative Fraction (RF) or Natural Scale:

1:1,000,000 (this is the same as 1/1,000,000)

The RF says that 1 of any measurement on the map equals 1 million of the same measurement on the original surface; for the example above 1 foot equals 1 million feet or 1 cm. equals 1,000,000 cm. This is the form of scale commonly used in the Map Collection. A good quality map should have both the RF and Bar Scales.

Large & Small Scale:

When we speak of large scale maps we are saying the RF is large, i.e. the RF's denominator is small. 1:10,000 and 1:62,500 maps are large scale. Small scale maps have a small RF. 1:500,000 and 1:1,000,000 maps are small scale.

How to Convert from one Form of Scale to Another:

Often when using cartographic materials it is useful to convert from one form of scale to another. If you have a good understanding of the concept of scale, the techniques are fairly simple. Here is an example of converting from Verbal Scale to RF. Remember, the RF has the same unit of measurement on both sides of the colon.

1 inch = 10 miles --> 1 inch = 10 x 63,360 inches (1 mile = 633,600 inches); RF= 1:633,600

To convert from RF to Verbal Scale you convert the fraction to familiar units of measurements; for example:

1:250,000 --> 1 inch equals 250,000 inches (63,360 inches = 1 mile);  Verbal scale = 1 inch equals 4 miles

Some Common Scales

Here is a list of RF scales commonly used in the Map Collection and their equivalent Verbal Scales.

1:24,000 - 1 in. = .379 mi.

1:250,000 - 1 in. = 4 mi.

1:62,500 - 1 in. = .986 mi.

1:500,000 - 1 in. = 7.891 mi.

1:100,000 - 1 in. = 1.578 mi.

1:1,000,000 - 1 in. = 15.783 mi.

 

How to Find Maps at a Particular Scale

Maps need to be located in the online catalog searching by the geographic area or subject heading to see what maps are available. You can search for maps using the Finding Maps

Map scales are usually given in the catalog using the RF form. A map series for a larger area may include the area you are interested in; so be sure to check for maps of larger areas such as countries or continents.

If you need assistance in locating a map at a particular scale please ask a staff member at the reference desk.

Topographic Maps for Arizona

Here is a list, from the largest scale to the smallest, of the various series of topographic maps available for Arizona. Many are now available online. 

U.S. Geological Survey. Arizona: topographic quadrangles A-H.  Scale 1:24,000, 1:62,500, and 1:125,000.
U.S. Geological Survey. Arizona: topographic quadrangles I-P.  Scale 1:24,000, 1:62,500, and 1:125,000.
U.S. Geological Survey. Arizona: topographic quadrangles Q-Z.  Scale 1:24,000, 1:62,500, and 1:125,000.

U.S. Army Map Service.  Arizona 1:50,000  Scale 1:50,000.  Coverage incomplete.

U.S. Geological Survey.  Arizona 1:50,000.  Scale 1:50,000. Coverage incomplete.

U.S. Geological Survey. 1:100,000-scale series (topographic).  Scale 1:100,000.

U.S. Army Map Service. Western United States 1:250,000.  Scale: 1:250,000. 1 x 2 Degree Series. 

Allan Cartography.  Arizona. Scale: 1:550,000.  

U.S. Army Map Service.  World 1:1,000,000. Scale 1:1,000,000.  4 sheets cover Arizona.

 

Last modified: June 3, 2013