Navigational Information

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Navigational information consists of isogonic lines and values, local magnetic disturbance notes, aeronautical lights, airway intersection depictions, and VFR checkpoints. Isogonic lines (lines of equal magnetic declination for a given time) provide the pilot with the difference between true north and magnetic north in degrees. These lines and values are updated every five years. Local magnetic notes alert pilots to areas where the magnetic compass might be unreliable, often due to large deposits of iron ore. 

Aeronautical lights at one time were a primary means of navigation —the lighted airways of the 1930s. Light symbols are depicted on visual charts for their navigational value; however, because electronic aids have taken over the majority of navigational needs, many of the old and large airport beacons have been replaced with smaller units. This can lead to confusion. The Bakersfield, California, Meadows Airport has one of the small, less-intense beacons, while the nearby Shafter Airport has the large unit. Pilots, including Army helicopter pilots, regularly key on the Shafter beacon, and even land at the wrong airport. The larger lights can often be seen twice as far as the smaller units. Airport rotating or oscillating beacons are indicated by a star adjacent to the airport symbol and operate sunset to sunrise. Rotating lights (with flashing code identification) and course lights are from the lighted airway days, and almost all have been decommissioned.

Named intersections that can be used as reporting points are depicted on some visual charts. The intersections consist of a fiveletter name and might be difficult to pronounce. Use of intersections by VFR pilots is limited because the cross-fix radial headings are not shown. Intersections made up of VOR radials are shown in blue; those made up with low-frequency radio beacons are shown in magenta.

Visual ground signs and VFR checkpoints that are easily recognizable from the air are depicted. Many visual signs are left over from the early days of aviation, have faded, and are of little value; others are large and prominent.

Special conservation areas a20re shown on sectional charts. Landing, except in an emergency, is prohibited on lands or waters administered by the National Park Service, U.S. Fish and Wildlife Service, or U.S. Forest Service without authorization. All aircraft are requested to maintain a minimum altitude of 2000 feet above the surface. The Yosemite National Park is one of these areas.

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