1. Field Values
A field value is any data or measurement that you have plotted on a map
EXAMPLES:
Elevation (Feet about sea level)
Temperature (at different locations)
Air Pressure (in different cities)

2. What are isolines? Lines drawn connecting equal field values
Iso means equal
Isotherm means equal temperature
Isobar means equal pressure
Contour lines connect equal elevations

3. Drawing Isolines

4. Basic Rules for drawing isolines
Isolines must have field values that are evenly spaced. This is called the isoline interval.
Isolines can never cross or touch each other
Isolines are generally smooth curves that either close in a loop or go off the page

5. Air pressure isolines

8. Earthquake Intensity Isolines