Meaning of pilot chart

pi'lot chart"

Pronunciation: [key]
  1. any of a number of charts issued to mariners by the U.S. Hydrographic Office and showing meteorological, hydrographic, and navigational conditions prevailing, or likely to prevail, subsequent to the date of issue in some part of the world: issued monthly for most areas.
  2. a chart giving information on atmospheric conditions at various altitudes.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.