database. If no terrain data is available in the terrain database,
then this area is displayed in a low-density magenta color.
Terrain more than 2000 feet below the aircraft, or within 400
(vertical) feet of the nearest runway elevation, is not displayed
(black). With version -218-218 or later, the transition to black
may occur below 400 feet based on runway and terrain
database integrity for a given area.