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

2. Examples of isolines: Isotherms: Isobar: Contour:
points of equal temperature
Isobar:
points of equal barometric (air) pressure
Contour:
points of equal altitude
Anything else you can get a value for.

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. Sample Contour Lines

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

12. 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

13. How to make contour lines.
Start by Highlighting data points for a value.

14. Then Fill in gaps in data; find the spot where the number would fall
Then Fill in gaps in data; find the spot where the number would fall. In this example 60 falls between 54 and 64 so the data point will be put there

15. Next you Connect the dots.

16. Go on to the next value and repeat the steps

17. Making a Contour Map: Obtain a practice sheet from your teacher and create contour lines for the values 70, 80, 90 and 100.