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Map Scale

What is Map Scale

Map scale is a statement that relates distance on a map to distance on the Earth’s surface. It is perhaps the most important information on a map, since the level of detail and map accuracy are both factors of the map scale.

Scale is directly related to the map extent, or the area of the Earth’s surface to be mapped. If a relatively small area is to be mapped, such as a neighborhood or subdivision, then the scale can be larger. If a large area is to be mapped, such as an entire continent, the scale must be smaller. Generally, the smaller the scale, the less detailed the map can be. As a rule, anything smaller than 1:250,000 is considered small-scale.

Type of Map Scales

Scale can be represents in several ways, including:

  • Representative fraction
  • Verbal statement
  • Scale bar

Representative Fraction

Map Scale is often noted as a simple ratio or fraction called a representative fraction. A map in which one inch on the map equals 25,000 inches on the ground could be described as having a scale of 1:25,000 or 1/25,000. The units on both sides of the ratio must be the same.

Verbal Statement

A verbal statement of scale describes the distance on the map to the distance on the ground. A verbal statement describing a scale of 1:1,000,000 is approximately 1 inch to 16 miles. The units on the map and on the ground do not have to be the same in a verbal statement. One-inch and 6-inch maps of the British Ordnance Survey are often referred to by this method (1 inch to 1 mile, 6 inches to 1 mile) (Robinson and Sale, 1969).

Scale Bars

A scale bar is a graphic annotation element that describes map scale. It shows the distance on paper that represents a geographical distance on the map. Maps often include more than one scale bar to indicate various measurement systems, such as kilometers and miles.

Map Scale Bars

Common Map Scales

Map Scale1/40 inch
represents
1 inch
represents
1 centimeter
represents
1 mile is
represents
1 kilometer is
represents
1:2,0004.200 ft56.000 yd20.000 m31.680 in50.00 cm
1:5,00010.425 ft139.000 yd50.000 m12.670 in20.00 cm
1:10,0006.952 yd0.158 mi0.100 km6.340 in10.00 cm
1:15,84011.000 yd0.250 mi0.156 km4.000 in6.25 cm
1:20,00013.904 yd0.316 mi0.200 km3.170 in5.00 cm
1:24,00016.676 yd0.379 mi0.240 km2.640 in4.17 cm
1:25,00017.380 yd0.395 mi0.250 km2.530 in4.00 cm
1:31,68022.000 yd0.500 mi0.317 km2.000 in3.16 cm
1:50,00034.716 yd0.789 mi0.500 km1.270 in2.00 cm
1:62,50043.384 yd0.986 mi0.625 km1.014 in1.60 cm
1:63,3600.025 mi1.000 mi0.634 km1.000 in1.58 cm
1:75,0000.030 mi1.180 mi0.750 km0.845 in1.33 cm
1:80,0000.032 mi1.260 mi0.800 km0.792 in1.25 cm
1:100,0000.040 mi1.580 mi1.000 km0.634 in1.00 cm
1:125,0000.050 mi1.970 mi1.250 km0.507 in8.00 mm
1:250,0000.099 mi3.950 mi2.500 km0.253 in4.00 mm
1:500,0000.197 mi7.890 mi5.000 km0.127 in2.00 mm
1:1,000,0000.395 mi15.780 mi10.000 km0.063 in1.00 mm

[Note : ft=feet, yd=yard, mi=mile, in=inch, m=meter, km=kilometer, cm=centimeter, mm=milimeter]

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