Legends

The elevation and configuration of the Earth's surface is important to pilots, and terrain shading is one way a sectional chart depicts this information. These color tints range from light green for the lowest elevations to brown for the higher elevations.

A tint box on the chart's title page gives the elevation for each color and notes the highest elevation on the chart. In this example, from the Wichita sectional, the highest terrain elevation is 8,720 feet mean sea level (MSL). The location of the chart's highest elevation is given in a text block next to the tint bar.

The text block also gives the format for the chart's other terrain elevation information. A boldface dot and figure denote a critical elevation, which is the highest elevation for a particular terrain formation. In the example, it's Mt. Dora, at 8,720 feet MSL.

If the dot and number are not boldfaced, it's a spot elevation, which gives the elevation of that particular point, such as the 7,355-foot "bump" southwest of Mt. Dora. If an x replaces the dot, the number is an approximate elevation. If no dot or x appears, the figure indicates the elevation of that particular area, such as the figures at the northwest base and midway up Mt. Dora, 7,000 and 8,000 feet respectively.

To show how the terrain might appear from the air, cartographers shade areas that would appear in shadow if illuminated by light from the northwest. According to the Aeronautical Chart User's Guide, "studies have indicated that our visual perception has been conditioned to this view."

Finally, sectional charts also use contour lines, which connect points of equal elevation, to depict terrain elevation and configuration. On sectional charts, cartographers space basic contour lines 500 feet (of elevation) apart. They may also show intermediate contours at 250-foot intervals and, occasionally, auxiliary contours at 50-, 100-, 125-, or 150-foot intervals.

The pattern created by the contour lines and their spacing gives pilots a visual concept of the terrain. Widely spaced contours represent gentle slopes, and closely spaced contours represent steep slopes.

S.M. Spangler