How to Create a Radius on a Map
Creating a radius on a map can give you straightforward, useful information. It can give a geographic limit in terms of miles or kilometers. Say, for example, you wanted to locate all state parks within 100 miles of Madison, Wisconsin. Using the capital as a center point, you simply draw a circle that corresponds to a scale of 100 miles and then you can easily obtain the necessary information.
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Things You'll Need
- High quality topographic or geographic map
- Drafting compass
- Soft lead pencil
- Eraser
Instructions
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Creating a Radius
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1
Choose a center point. For example, if you want to find out who lives within 5 miles of the state capitol building in Madison, Wisconsin, you will need at least one topographical map, perhaps more, if the capitol building is not located centrally on the map.
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2
Lay the map on a solid desk or table that is large enough to hold the entire map. Find the state capitol building. In this case, the building is not difficult to find because it is located on a narrow strip of land that is located between Lake Mendota and Lake Menona.
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3
Find the scale and find the corresponding scale for converting miles to inches. If 1 mile equals 1 inch, then you know that anyone living within 5 miles of the capitol will require a circle with a radius of 5 inches.
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4
Draw the circle with a radius of 5 inches. Set the compass at 5 inches, place the metal point in the center of the capitol building and move the pencil across the map until the circle is complete.The center of the large symmetrical building will be the center of the circle and the radius will be 5 inches, but the diameter, the distance across, will be 10 inches.
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5
Erase the circle when you are done to keep your map as clean as possible.
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1
Tips & Warnings
Two maps can be placed side-by-side if the need arises.
Only use a soft pencil to scribe the circle, so it can be erased later.
