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
Tube map no complete maps of the network, just for the individual companies' routes. These maps were not typically schematic and were simply the line overlaid on a regular city map. There was no integration of the companies' services, nor was there any co-operation in advertising. In 1907, "The Evening News" commissioned a pocket map titled The Evening News London "Tube Map". This map was the first to show all of the lines with equal weight given to each line. In addition, it was the first to use a different colour for each line. Another early combined map was published in 1908