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

2. Examples of isolines: (The weather channel loves 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!)

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

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

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

9. 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

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

11. 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

12. 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

13. Visualizations of contour lines

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

16. A gentle (low) gradient changes slowly and the lines are far apart.
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

17. Making Contours worksheets
Worksheets can be printed from:

18. Highlight data points.

19. Fill in gaps in data.

20. Connect the dots.

21. Go on to the next value.

22. Making a Contour Map II

24. Drawing Contour Maps III