Contour line factors in a weather system. An isobar (from or "baros", meaning 'weight') is a line of equal or constant pressure on a graph, plot, or map; an isopleth or contour line of pressure. More accurately, isobars are lines drawn on a map joining places of equal average atmospheric pressure reduced to sea level for a specified period of time. In meteorology, the barometric pressures shown are reduced to sea level, not the surface pressures at the map locations. The distribution of isobars is closely related to the magnitude and direction of the wind field, and can be used to predict
Map symbolization locations. These symbols can be true points or conceptual points. True points represent real objects or the exact location of a tangible object. This could be an oil well or fire hydrant. A conceptual point represents the center of the enumeration unit, such as a corn field. The raw data on proportional symbol maps go hand in hand with the data shown on choropleth maps. Isopleth maps use isolines that connect points of equal values. A good example of isolines is connecting areas with similar temperatures. As with choropleth maps, Isopleth maps require standardized data to be appropriately contoured. Dot