1. How can we describe fields, isolines, and gradients on maps?
Aim:
How can we describe fields, isolines, and gradients on maps?

2. Isolines
Lines that connect points of equal field values

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

5. Field
Any region of space that has a measurable quantity at every point
Examples: gravity, magnetism, temperature, sound levels, elevation, depth, pressure, wind speed…..etc

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

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

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

10. 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

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

12. Highlight data points.

13. Fill in gaps in data.

14. Connect the dots.

15. Go on to the next value.

17. A bit more practice with isolines!
Let’s put in a 10ft contour interval line!

18. A bit more practice with isolines!
Let’s put in a 10ft contour interval line!
Well, where would
10 be?
Beteween HERE!

19. A bit more practice with isolines!
Let’s put in a 10ft contour interval line!
Well, where would
10 be?
HERE

20. A bit more practice with isolines!
Let’s put in a 10ft contour interval line!

21. A bit more practice with isolines!
Let’s put in a 10ft contour interval line!
Don't forget up here too!

22. A bit more practice with isolines!
HOW ABOUT THE 20?

23. A bit more practice with isolines!
HOW ABOUT THE 30?

24. A bit more practice with isolines!
What if we were to use a 5ft contour interval?
steep
flat

25. Gradient
Gradient shows how quickly the value change from one point to another.
Rate of change from place to place

26. 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

27. Calculate the gradient between our school and the upper field!
From your ESRT (front cover)
High School
Elevation = 350ft
Football Practice Field
Elevation = 415ft
250 yards

28. =415ft – 350ft 250 yards High School Football Practice Field
Elevation = 350ft
Football Practice Field
Elevation = 415ft
250 yards

29. = .26 ft/yrd = 65 ft 250yds High School Football Practice Field
Elevation = 350ft
Football Practice Field
Elevation = 415ft
250 yards

30. How about from this view?
800
700
600
500
400
300
200
100
Elevation Of
Cliff x Y
Distance
Calculate the gradient between points X and Y

31. How about from this view?
800
700
600
500
400
300
200
100
Elevation Of
Cliff (feet) x Y
Distance (miles)
Calculate the gradient between points X and Y
500ft – 100ft
400/3= ft/mile
3 miles