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
Closest pair of points problem left of the dividing line we have to compare the distances to the points that lie in the rectangle of dimensions bordering the dividing line on the right side, as shown in the figure. And what is more, this rectangle can contain at most six points with pairwise distances at least . Therefore, it is sufficient to compute at most left-right distances in step 4. The recurrence relation for the number of steps can be written as , which we can solve using the master theorem for divide-and-conquer recurrences to get . As the closest pair of points define an