![Sample our Geography journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/5937/TOC-Subject-Sample-2021-Geography.jpg"})
Abstract
The practice of measuring depths and positions at sea has traditionally been divided into hydrography and bathymetry. NOAA's National Ocean Service (NOS) is at the forefront of a technological revolution that is causing the distinctions between these disciplines to blur and disappear. A unified marine geographic information system is emerging.
Hydrography has been a highly disciplined practice, focused in shallow water and oriented toward producing charts for the surface navigator. Great effort has been expended to meet international accuracy standards and ensure that no obstructions are missed between sounding lines. While providing for the safety of navigation, these efforts have not always been able to provide the information about the sea floor needed by ocean engineers, scientists, and fishermen. Bathymetry, on the other hand, has been an art. Cartographers and marine geologists have used all available data together with their concepts of seafloor shapes to produce bathymetric maps. There were often large errors in the data due to the sparcity of sounding data and the inaccuracy of the depth and positioning instrumentation used. Bathymetric maps neither met the accuracy standards for nautical charts nor did they show the navigational aids available in an area and, therefore, they have almost always been marked “not to be used for navigation.”;
Today, however, new technology is making possible mapping systems that can provide complete, accurate, and efficient coverage of the seafloor. Examples of depth measuring systems include multibeam sonars such as SeaBeam, interferometric and multibeam side scan sonars, laser and electromagnetic “sounders,”; and multispectral scanners. Almost all positioning needs will soon be met by some technique involving the Global Positioning System (GPS). These systems promise to improve the quality of marine geographic data, the usefulness of these data to mariners, scientists, and engineers, and the cost‐effectiveness of operations.