Topographic Maps

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Topographic Maps

• Topic 2.2
• Regents Earth Science

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Gradient aka slope

• The rate of change between 2 places within a field

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Equation ESRT page 1
fv
g
d
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field

• A region in space that has some measurable value
  at every point in that region
• Examples - the amount of rainfall - the odor
  of food along Grant Ave - wind speed

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Field map

• A map on which the field values are plotted

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Isolines connect points of

• Equal value on a field map

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Isotherms connect points of equal

• temperature

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Temperature field map
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Isobars connect points of equal

• Air pressure

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Air pressure field map
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Contour lines connect points of equal

• elevation

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Elevation field map
Contour line
Contour line
Contour lines are brown on topographic maps.
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Topographic Maps aka contour maps

• A map on which elevations of the surface are
  shown by lines
• The contour lines make a picture of the land
  surface
• Colors and symbols are used to show natural and
  manmade features

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Contour Pictures
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Index contour

• Thicker contour line that is labeled with the
  elevation

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Index contour
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Contour interval

• The difference in elevation between 2 consecutive
  contour lines

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Contour interval 20 meters
980
1020
980
Scale of miles
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depression

• A crater or a dip on a map (the elevation goes
  down here instead of up)
• Shown by contour lines that are marked on the
  inside
• These marks are called hachure lines

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depression
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Reading depression contours

• The first one is read at the same elevation as
  the ordinary contour line that comes before it.
• After that, each contour line is lower than the
  one before by an amount equal to the contour
  interval.

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Depression
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Bench mark

• A place where the exact elevation is measured and
  marked

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Bench mark
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Bench mark
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Gradient

• Where the contour lines are far apart, the land
  is flatter with a gentle slope. (small gradient)

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flat
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Gradient

• Where the contour lines are close together, the
  land is steep. (high gradient)

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steepest
steep
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How are streams shown?

• Contour lines bend uphill when they cross streams
• The v points uphill so the stream flows in the
  opposite direction

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uphill
The V
downhill
The Moose Creek flows southeast.