Legends

The elevation and configuration of the Earth's surface are important to pilots, so cartographers devote a lot of attention to depicting the terrain's relief on sectional charts. Among the devices they use to accomplish this is contour lines.

Like isobars that connect areas of the same barometric pressure, contour lines connect points on the Earth that have the same elevation above mean sea level. On sectional charts, basic contours are spaced at 500-foot intervals. Some of them are labeled with the MSL altitude such as the 6,500-foot contour in the example, which is for a peak just north of Mount Shasta on the Klamath Falls sectional chart.

In moderately level or gently rolling areas the chart might depict intermediate contours, which represent 250-foot intervals. Occasionally, auxiliary contours at 50-, 100-, 125-, or 150-foot intervals may be used to portray smaller relief features in areas of relatively low relief.

The pattern that contour lines create - and their spacing - give pilots a visual concept of the terrain. Widely space contours represent gentle slopes, and closely spaced contours represent steep slopes. For instance, the slope is relatively gentle near the Coonrod private airport, which has an elevation of 3,010 feet. The contour lines quickly get closer together as they approach the peak, and you can determine each contour's elevation by counting up from the contour nearest the airport - or the labeled 6,500-foot contour - in 500-foot increments. The peak's elevation, 8,280 feet MSL, is in black next to the black dot that depicts its location.