[symbology]
A line that connects points of equal measured or derived values on a map, such as elevation or temperature. Example values that can be measured or sampled at an individual point include the elevation above sea level, the measured daily high temperature or daily rainfall, and so on. Examples values that can be derived at an individual point include estimates, averages, and ratios—such as the average daily temperature or the ratio of cloudy to sunny days, and so on.
