Contour plot

Here is a hypothetical example (no longer of Penang Hill) showing a contour plot side by side with its corresponding elevation plot. Points A, C and E are peaks — as we approach the heart of each point, the elevation increases. Points B and D are valleys — as we approach the heart of each point, the elevation decreases. The surrounding area is between 30 and 35. Point A is 70. Point B is 20.