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) pressureContours:

points of equal altitudeConcentration of chemicalsAnything 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

5 5

1510

1010

10

2. Isolines are gentle, curving lines- no sharp corners.

15

5 5

1510

1010

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….