1. An isoline is a line connecting points of equal value.
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
Concentration of chemicals
Anything else you can get a value for.
(The weather channel loves isolines!)

6. Rules for Drawing Isobars:
1. ALL points on an isobar have the EXACT same pressure 5 5
10
10
10
10
15
15

7. 2. Isobars are drawn at intervals
2. Isobars are drawn at intervals. Each isobar will have a side where values are higher and a side where values are lower. 5 5
10
10
10
10
15
15

8. 3. Isobars NEVER cross or fork (split):
a. Either form closed circles/loops
b. Run off the edge of the map
c. You may stop at a front line

9. 4. Isobars are ALWAYS labeled.
60 °
50 °
40 °
30 ° X
20° Z Y

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

11. 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

12. Highlight data points.

13. Fill in gaps in data.

14. Connect the dots.

15. Go on to the next value.

16. Making a Contour Map II

18. Drawing Contour Maps III