Early Hydrographic Surveys Accurate and reliable information on the features of water bodies and their shorelines is vital to navigation safety. Hydrographic surveys gather this information that is then published for use by mariners on nautical charts and other publications such as Coast Pilots. NOAA and its predecessor agencies have been conducting hydrographic surveys for 200 years since President Thomas Jefferson ordered a survey of the nation's coast and Congress authorized the U.S. Coast Survey in 1807. Since that time, NOAA has conducted over 11,600 hydrographic sur- Lead lining hydrographic survey party. This method of measuring water depth was done from a slow moving vessel and was practicable only in depths of about 10 fathoms (60 feet) on small launches or 15 fathoms (90 feet) on ships. (Photo Credit: NOAA) veys. Over those years, several breakthroughs have vastly improved NOAA's ability to carry out its original mission to survey the nation's coast both in measuring depth and in establishing the position of ships taking those measurements. Hydrography is the science of measuring the physical features of water bodies and surrounding lands. Two major elements of a hydrographic survey are water depth and position (loca(Continued on page 25) www.seadiscovery.com Marine Technology Reporter 21
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