A contour plot is a graphical representation of 3-dimensional data in the form of plotted z slices on a 2-dimensional graph. These z slices are referred to as contours, isolines, isarithms, and isopleths. The lines of the graph are a function of two variables, which produces curves that connect the points where that function has the same specified value. Contour plots are widely recognized for their use in cartography, but they are also employed in other sectors and disciplines: meteorology, environmental science, social science, and more.
Contour plots were originally used in the early 1700s by Edmond Halley to express magnetism. Every twenty years from that point, another engineer utilized the tool in different way, but they were primarily used in geography and oceanography. Use of contour plots was adopted by Great Britain's Ordnance Survey by the mid-1800s, which then formally introduced them into popular use. When contour plots became common (in the form of maps), people began to develop other applications for contour plots.
Contour plots are used in meteorology to express a variety of things. Contour plots can express barometric pressure over land and its movement. They can also express temperature over land and its movement. They also express air moisture and precipitation, freezing and thawing, and wind; and also the movements of these qualities.
In the realm of environmental science, contour maps are used to monitor things like soil contamination, air pollution, and groundwater contamination. In finance, contour maps can be used to review metrics like the cost of transporting goods from a source, but their usage is not limited to information related to geography. They can also be used to analyze things like the production costs of different input combinations. Some use contour graphs to analyze things like changes to population size and characteristics, and others will analyze political behavior within a population.