Contour line

A contour line or isopleth or levelset for a function of two variables is a curve connecting points where thefunction has a particular value. A contour map is a map showing many contourlines.

The gradient of the function is always perpendicular to the contour lines.

When the lines are close together the gradient is large, i.e. the variation is steep.

Different types of contour lines are given different names according to the nature of the quantity involved:

• elevation : contour lines on a topographic map
• pressure : isobar .
• temperature : isotherm .
• dew point : isodrosotherm .
• humidity : isohume .
• wind speed: isotach .
• wind direction: isogon .
• liquid precipitation amount: isohyet

"iso" can be replaced with "isallo" to give it the meaning of a line connecting points where some variable has changed at thesame rate during some time period.

Synonyms : isogram, isarithm

Example

See also

• level set

External links

• Drawing Contour Plots . A lesson plan that dealswith drawing various isopleths.

• See also Forthright's Phrontistery for many more different types of isopleths.