Isolines and Topographic Maps

Isolines An isoline is a line connecting points of equal value.

Examples of isolines: Contour: points of equal elevation Isotherms: points of equal temperature Isobar: points of equal barometric (air) pressure

Topographic Maps Contour Line – - line on a map that connects points of EQUAL elevation. - show elevation and shape of the land

“Real World” Contour Map

Topographic Maps Two dimensional model of the Earth’s surface (represents 3-D world) Topographic maps are also known as contour maps. Show elevation above sea level using contour lines.

Topographic Maps Contour Interval – difference in elevation between each line. MUST be equal spacing. Contour interval = 20 feet 580 560 540 520

How to draw isolines 1.) Isolines connect points of equal value 2.) Values of one side of an isoline are lower, while all values to the other side are higher. 3.) Isolines never cross one another

How to draw isolines 4.) Isolines never end, so they should be drawn to the end of the map or for a closed loop. 5.) Isolines tend to be parallel to one another 6.) Isolines are curves and/or smooth with no sharp turns or corners.

Do Now Do the Worksheet labeled “Contour Map Practice”

Rules for Contours 1. Contours bend upstream (uphill) when crossing a stream.

Rules for Contours 2. The maximum possible elevation for a hill is “1” less than what the next contour “should” be. The highest possible elevation of the hill is just below the value of  the next line that is not shown 90 80 70 60 50

399 179 239

Closely Spaced Contours Steeper Slope (Gradient) – contour lines are closer together.

Wide Spaced Contours Gradual/Gentle Slope (Gradient) – contour lines are farther apart.

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