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Fields & Isolines
Field: region of space which there is a Measurable quantity of a given
property at every point.
EXAMPLES:AIR TEMP
AIR PRESSUREELAVATIONRAIN FALL
VOLCANIC ASH FALL
Maps of Fields have:
1. SCALE: showing relative
size of model
2. Isolines: lines connecting points of the equal value
in the fieldpoints may be measured or interpolated.
Examples of 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!)
3. Interval: spacing between isolines.
Rules for Drawing Isolines:1. Isolines connect points of equal value.
15
55
1510
10
10
10
2. Isolines are gentle, curving lines- no sharp corners.
15
55
1510
10
10
10
3. Isolines are always closed curves even though the map might only show part of it.
4. Isolines NEVER cross- this would mean that one point has two different values. Ex: one spot has two temperatures?
20°
30 °
40 ° 50 ° 60 °
X
YZ
Isolines NEVER cross
5. Isolines usually are parallel. (They have a parallel trend.)
Highlight data points.
Fill in gaps in data.
Connect the dots.
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.
Go on to the next value.
The interval will be 10 degrees
Making a Contour Map II
Drawing Contour Maps III
GradientGradient shows how quickly the value
changes from one point to another.
Gradientvalue
dis c e
tan
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
1. CLOSELY spaced = steep gradient, rapid change
2. WIDELY spaced = gentle gradient, slow change
Time to practice….
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