![]() How might we estimate the height of this peak? Clearly, we do not have two contours to use. What about closed contours that have no other contours drawn within them? Look again at the contour map and focus your attention on the southern-most peak, Mauna Loa. Using interpolation usually provides us with a sufficient approximation, but we must always realize that it's only an estimate. In this case, we can see that point "P" is about half-way between the two contours and thus has an elevation of approximately 3,500 feet. In such cases, we can interpolate (make an estimate by assuming the elevation changes linearly) between the two known contours. However, often instead of giving a range of elevation, we would prefer a single number. Technically, this is all that we can say for sure about the elevation at point "P" - it can be anywhere between 3,000 and 4,000 feet. We know that point "P" is not equal to either of these values because it does not lie on one of the contour lines. On our map, point "P" lies between 3000 feet and 4000 feet contours, so the elevation at point "P" is greater than (but not equal to) 3000 feet but less than (but again, not equal to) 4000 feet. ![]() How would we go about figuring out the elevation of the point marked "P"? First, we must identify the two contours that lie on either side of "P." In some cases the contours that we need are clearly labeled however, in other instances, you will need to use the contour interval (1,000 feet, in this case) to "count" up or down from a labeled contour. ![]() To get us started on interpreting contour maps, we're first going to revisit our topographic map of Hawaii (right). Meteorologists regularly use contour maps to see how weather variables (temperature or pressure, for example) change over large areas, but they also use them to estimate values of weather variables at individual points. ![]()
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