CHARTING THE OCEANS FOR SAFE NAVIGATION 



NAUTICAL CHARTING 



For the past 130 years the U. S. Navy ha& been producing 

 nautical charts on a world-wide basis in order to secure maximum 

 navigational safety for ships of the Navy and merchant marine. 

 The earliest charts were made from exploratory surveys of a 

 reconnaissance nature. Through the years the charts have been 

 considerably improved to meet the growing needs of modern 

 shipping by the addition of more accurate, detailed sounding data 

 obtained by electronic surveying systems, by the extensive use of 

 aerial photography for the interpretations of land masses and 

 coastal configurations, by the application of geodetic control 

 positioning for more precise navigation, and by improvements in 

 cartographic presentation and reproduction methods. The 

 requirements of safe navigation govern the selection of nautical 

 chart content, detailed portrayal of which is commensurate with 

 the scale and purpose of the chart. First emphasis is given to the 

 most important features of the chart, namely, the soundings and 

 depth curves by which the main characteristics of the configuration 

 of the ocean bottom — sunken rocks, wrecks, and other obstructions 

 and dangers to navigation are charted in detail. Current and 

 tidal data are included. Symbols are employed to portray sub- 

 marine relief for features such as coral and rock reefs, shoals, 

 banks, etc. Abbreviations for bottom sediment characteristics, 

 such as mud, sand, shell, etc., are shown. Also portrayed are 

 principal aids to navigation such as buoys, lights, lightships, day- 

 beacons, and radio beacons. Aids with their identifying 

 characteristics must be charted so that they can be readily 

 identified without confusion to the chart user. 



Topographic detail shown on nautical charts is compiled in 

 accordance with the needs of the mariner, an accurate delineation 

 of such detail being useful for fixing positions at sea. Extensive 

 use is made of Navy and other aerial photographic surveys for 

 compilation and revision of topographic detail. Coastlines, 

 important rivers, contours, spot elevations, and other topographic 



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