Mapping Scale

Index

Definition of Map Scale Determining Map Scale Ground and Map Distances
English Measurement Metric Measurement English/Meteric Conversion


Map Scale

Cartography is the art, science, and technology of creating maps. The use of scale allows a cartographer to graphically represent a geographic area.

Map scale is defined as the ratio between map distance to earth distance. Small scale maps show large geographic areas, showing less detail. Large scale maps show small geographic areas, showing more detail.

A maps scale will directly influence the size of the phenomena being represented on the map.
For example, a ground area of 300 x 300 meters square would be 4.80 x 4.80 milimeter square on a 1:62,500 scale map (small scale), while the same area would be represented as 12.80 x 12.80 milimeter square on a 1:24,000 scale map (medium scale). In, general, 'the larger the scale the more detail, the smaller the scale the less detail.'



Scale can be represented as one of the following: verbal, ratio, or graphic scale.

A verbal scale would be a statement found on the map telling a map reader the relationship between the map distance and earth distance. An example would be, "3cm on the map equals 1Km".

A Ratio scale is a representative fraction (RF) that expresses one unit of a measurement on the map, in either english or metric units, is equal to the number of the same units on the earth. Example: if 1cm was measured on a map with RF 1:24,000, the earth distance would be equal to 24,000cm which when converted to meters would be equal to 240m; or 1 inch on a map with a scale of 1:24,000, the earth distance would be equal to 24,000inches which when converted to feet would be equal to 2000ft.

A graphic scale is a graphic divided into segments showing the distance on a map labeled with the earth distance it represents.
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Determining Map Scale


Determine:FormulaExample
Fractional Scale From a Bar Scale
Map Scale
Map Distance for a Specific Ground Distance
Map Distance
Ground Distance from a Map Distance
Ground Distance
Representative Fraction (RF) from a Verbal Scale
RF


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Determine Fractional Map Scale from a Bar Scale

Thus, a bar scale with a map distance of 16.67mm, with an earth distance of 400m, would have an RF scale of 1:24,000.

Determine a Map Distance with a Specific Ground Distance

Thus, 4.167cm measured on a map with a scale of 1:24,000 would equal 1Km on the earth.

Determine Ground Distance from a Measurement Taken From a Map

Thus, a measurment of 2.5cm from a map with a scale of 1:24,000 would equal 600m on the earth.

Determine RF from a Verbal Scale

Thus, the RF of the verbal scale of "3cm equal to 1Km" would be equal to 1:33,333.

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Ground Measurement Distances



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English Measurements

  • 1 mile = 1760 yards
  • 1 mile = 5280 ft
  • 1 mile = 63360 inches

  • 1 yard = 3 feet
  • 1 foot = 12 inches
  • (Acres) x (.4047) = hectares
  • (Acres) x (43,560) = square feet
  • (Acre) x (0.00156) = square miles
  • (square miles) x (640) = acres

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Metric Measurements

  • 1 Kilometer (Km) = 1,000 meters (m)
  • 1 Kilometer (Km) = 100,000 cm
  • 1 Kilometer (Km) = 1,000,000 mm

  • 1 meter = 100 centimeters (cm)
  • 1 centimeter = 10 millimeters (mm)

  • (square kilometer) x (100) = hectares

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Engilsh-Metric Conversion

  • 1 mile = 1609.35 meters
  • 1 foot = 0.3048 meters
  • 1 inch = 2.54 cm

  • 1 square foot = 0.0929 square meters
  • 1 square foot = 6.4516 square centimeters
  • 1 Km = 0.6214 miles
  • 1 meter = 39.370 inches
  • 1 cm = 0.3937 inches
  • 1 mm = 0.033937 inches
  • 1 square Km = 0.3861 square miles

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Reference
Dent, B.D. 1993. Cartography Thematic Map Design, Third Edition . Dubuque, Iowa: Wm. C. Brown Publishers. ISBN 0-697-13589-6.

French, T.E., C.J. Vierck, and R.J. Foster. 1986. Engineering Drawing and Graphic Techology. New York: McGraw-Hill Book Company. ISBN 0-07-022161-8.


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