The Federal Aviation Administration produces sectional charts used by pilots of aircraft flying under Visual Flight Rules (VFR.) Sectionals impart a prodigious amount of information vital to safe flying including airspace classification, radio frequencies, waypoints and navigation aids. Other information critical to pilots relates to maximum ground elevation of areas the aircraft is flying over. Accurate estimates of changes in ground elevation prevent collision with terrain or manmade vertical obstructions. Sectional charts graphically depict information about ground elevation in four ways.
Instructions
1. Look for contour lines on sectional charts. Contour lines, familiar from topographical maps hikers and campers use, also appear on sectional charts to depict changes in ground elevation. The pattern of the lines and the spacing between them represent ground elevation gain or loss. Widely-spaced contours indicate gentle slopes, while contours spaced tightly together indicate steep terrain with sharp increase in elevation.
2. Notice the shading of mountains and valleys. Shaded relief visually represents changes in ground elevation as they would appear if viewed from the air. Cartographical techniques apply shading to hills and mountains on sectionals to depict relative elevation and steepness. The eye perceives the degree of elevation and steepness according to the depth and amount of shadowing on hills, valleys and mountains.
3. Pay attention to background colors of sectional charts. Color tints that superimpose over areas of a sectional indicate general areas of ground elevation. Light green tints represent the lowest ground elevations, and dark brown tints represent the highest.
4. Keep your eye on the MEF. The Maximum Elevation Figure (MEF) on sectional charts is a number expressing the highest elevation in any given quadrant. The MEF calculation takes the highest elevation of terrain above mean sea level in the quadrant and adds a possible error factor (usually 100 feet) plus a 200-foot allowance for manmade or natural objects such as trees which may protrude vertically above the terrain. The total rounds off to the next higher hundred feet. The MEF appears on sectionals as a colored large font number representing thousands of feet, followed by a smaller font number representing hundreds of feet. An MEF expressed as large font 2 followed by smaller font 5 indicates maximum elevation of the terrain (plus an allowance for manmade obstacles) is 2,500 feet.
Tags: ground elevation, sectional charts, changes ground, changes ground elevation, aircraft flying