Contour plots | Multivariable calculus | Khan Academy
10:26
Level curves | MIT 18.02SC Multivariable Calculus, Fall 2010
7:54
Visualizing Multi-variable Functions with Contour Plots
6:17
Gradient and contour maps
10:03
Lecture 4 Graph; Level curves; Contour lines of functions of two variables
A contour line of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional graph of the function f(x, y) parallel to the x, y plane. In cartography, a contour line joins points of equal elevation (height) above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes. The contour interval of a contour map is the difference in elevation between successive contour lines.