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Isolines

Isolines. An isoline is a line connecting points of equal value. Examples of isolines:. Isotherms: points of equal temperature Isobar: points of equal barometric (air) pressure Contour: points of equal altitude or elevation Anything else you can get a value for.

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Isolines

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

  2. Examples of isolines: • Isotherms: • points of equal temperature • Isobar: • points of equal barometric (air) pressure • Contour: • points of equal altitude or elevation • Anything else you can get a value for. • (The weather channel loves isolines!)

  3. Rules for Drawing Isolines: • 1. Isolines connect points of equal value. 5 5 10 10 10 10 15 15

  4. 2. Isolines are gentle, curving lines- no sharp corners. 5 5 10 10 10 10 15 15

  5. 3. Isolines are always closed curves even though the map might only show part of it.

  6. 4. Isolines NEVER cross- this would mean that one point has two different values. Ex: one spot has two temperatures? 60 ° 50 ° 40 ° 30 ° X 20° Z Y

  7. 5. Isolines usually are parallel. (They have a parallel trend.)

  8. Isoline and Contour Line Rules • Contour line must never split or divide • Contour lines must never simply end except at the edge of a map • Contour lines represent one and only one elevation • Contour lines may never intersect other contour lines. Overhanging cliffs are the exception

  9. Rules continued • Contour lines form a V-pattern crossing streams. • V will always point upstream • Contour lines close together represent a steep slope or gradient, widely spaced lines indicate a gentle slop. • Concentric circles of contour lines indicate a hill top or mountain peak • Concentric circles of hachured contour lines indicate a closed depression

  10. Visualizations of contour lines • http://geology.asu.edu/~sreynolds/topo_gallery/topo_gallery.htm

  11. Gradient • Gradient shows how quickly the value changes from one point to another.

  12. A steep (high) gradient changes quickly and the isolines are close together. • A gentle (low) gradient changes slowly and the lines are far apart. Steep area Gentle area

  13. Making Contours worksheets • Worksheets can be printed from: • http://www.rcmurphy.net/Medina%202005/documents/Contours123.doc

  14. Highlight data points.

  15. Fill in gaps in data.

  16. Connect the dots.

  17. Go on to the next value.

  18. Making a Contour Map II

  19. Drawing Contour Maps III

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