1. | Determine
the maximum and minimum values plotted on the map. | |

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2. | Determine a
contour interval that best describes the range of data and the detail you wish to show. If
possible, use an interval that produces contour lines with whole numbers. Contour
intervals of 2, 5, 10, 20, 50, and 100 work well for a variety of topographic maps. | |

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3. | Write out
the contour lines necessary to accommodate your data. The highest contour line should be
slightly less than the maximum value plotted and the lowest contour line less than the
minimum value. | |

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4. | Find and
mark all the points with values equal to or greater than the highest contour line. | |

| a. | Draw a line
through all the points with values equal to that of the contour line. | | | b. | Circle
those points which are higher, and exclude points with values lower than the contour line. | | | c. | Draw the
contour line close to points with values similar to that of the contour line and far away
from those points significantly different. |
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5. | Mark all
points with values between that of the contour line you just drew and the next lower
contour line. | |

| a. | Circle this group of points with the
next lower contour line. | | | b. | Position the line as described in
step 4. |
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6. | Repeat this
procedure until you have contoured the entire map. | |

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