Fields & Isolines
Field: region of space which there is a Measurable quantity of a given property at every point.
EXAMPLES: AIR TEMP AIR PRESSURE ELAVATION RAIN 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 field points may be measured or interpolated.
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!)
3. Interval: spacing between isolines.
Rules for Drawing Isolines: 1. Isolines connect points of equal value. 5 5 10 10 10 10 15 15
2. Isolines are gentle, curving lines- no sharp corners. 5 5 10 10 10 10 15 15
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? 60 ° 50 ° 40 ° 30 ° X 20° Z Y
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
Gradient Gradient shows how quickly the value changes from one point to another.
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
1. CLOSELY spaced = steep gradient, rapid change 2. WIDELY spaced = gentle gradient, slow change
Time to practice….