1. Fields & Isolines

2. Field: region of space which there is a
Measurable quantity of a given property at every point.

3. EXAMPLES: AIR TEMP AIR PRESSURE ELAVATION RAIN FALL VOLCANIC ASH FALL

9. Maps of Fields have: 1. SCALE: showing relative size of model

10. 2. Isolines: lines connecting points of the equal value in the field
points may be measured or interpolated.

11. Examples of isolines: (The weather channel loves isolines!) Isotherms:
points of equal temperature
Isobars:
points of equal barometric (air) pressure
Contours:
points of equal altitude
Concentration of chemicals
Anything else you can get a value for.
(The weather channel loves isolines!)

15. 3. Interval: spacing between isolines.

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

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

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

19. 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

20. Isolines NEVER cross

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

23. Highlight data points.

24. Fill in gaps in data.

25. Connect the dots.

26. An isoline needs to be drawn for every interval.
If the interval is 20 meters, then you draw an isoline every 20 meters.
If the interval is 4 isobars, then you draw an isoline every 4 isobars.
You do NOT draw a line for any amount other then the interval amount.

27. Go on to the next value.
The interval will be 10 degrees

28. Making a Contour Map II

30. Drawing Contour Maps III

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

33. 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

34. 1. CLOSELY spaced = steep gradient, rapid change
2. WIDELY spaced = gentle gradient, slow change

35. Time to practice….