The history of ocean surveying and mapping

As early as ancient times, humans fished and sailed on the sea, which created the need for ocean surveying and mapping. Ancient Greek scholars were able to draw maps representing the oceans in the 1st century BC. In the 3rd century AD, during the Wei and Jin Dynasties of China, the "Island Calculation Classic" written by Liu Hui already contained content on the measurement methods of the distance and height of islands. "Pingzhou Ke Tan" written by Zhu Yu of the Song Dynasty in China in 1119 records: "The boat master knows the geography. He watches the stars at night and the sun during the day. He can know by looking at the compass in the dark or using a ten-foot-long rope hook to sniff the mud on the bottom of the sea. "It shows that there were methods of measuring the sky and smelling mud to estimate the ship's position.

The earliest extant nautical chart that directly serves maritime activities is the "Portland" (navigational direction) type nautical chart of the Mediterranean area produced around 1300. This kind of chart has compass bearing lines centered on several points. In the mid-15th century, the Chinese navigator Zheng He sailed to Africa. He conducted some water depth measurements and sediment exploration along the way, and compiled a nautical atlas (see "Zheng He's Nautical Charts"). The activity of navigation and exploration in the 15th and 16th centuries greatly promoted the development of ocean surveying and mapping. When Portugal compiled nautical charts in 1504, it used a point-by-point notation method to express water depth. This was the beginning of the basic method of representing seabed landforms on modern nautical charts. In 1569, G. Mercator compiled nautical charts using the equiangular cylindrical projection. This method is still used by various countries today. After the 17th century, the scope of ocean surveying and mapping expanded day by day, and the content of nautical charts continued to increase. In the 18th century, many European countries successively established hydrographic institutions, began to conduct systematic hydrographic surveys of their coastal sea areas, and compiled a series of nautical charts. During this period, nautical charts using contour lines to represent seafloor landforms also appeared. In the 19th century, ocean surveying and mapping developed from coastal sea areas to the ocean. The continuous increase in ocean measurement data provided conditions for the preparation of world ocean bathymetry maps. At the 7th International Geographic Congress held in Berlin in 1899, it was decided to publish the "Oceanic Relief Map", and the first edition was published in 1903. In the 1920s, echo sounders began to be used in water depth measurements, which greatly improved work efficiency. After the establishment of the International Hydrographic Bureau in 1921, it carried out academic exchange activities, revised the "Ocean Relief Chart", and successively published the "International Nautical Chart" for international navigation, promoting international cooperation. Beginning in the 1940s, aerial photography technology was experimented with in ocean surveying and mapping. Since the 1950s, ocean surveying and mapping have made significant progress in applying new technologies and expanding research content. In terms of bathymetry, in addition to using single-beam echo sounders, side-scan sonar and multi-beam bathymetry systems have been used, and ocean remote sensing bathymetry has also achieved initial success. Positioning methods have evolved from the use of optical instruments to the widespread use of electronic positioning instruments. The positioning accuracy has been improved from thousands of meters or hundreds of meters to tens of meters or several meters. The processing of measurement data has adopted electronic computers. Since the 1970s, major coastal countries have planned to use space technology to conduct ocean geodesy and various ocean physical field measurements (such as ocean magnetometry). In particular, satellite altimetry technology has been used to conduct relatively detailed detection and research on ocean geoid, gravity anomalies, ocean circulation, ocean tides and other issues. Technologies such as automatic coordinate instrument positioning, electronic color separation scanning, electrostatic copying and computer-aided drafting have been widely used in the process of chart creation. Oceanographic surveying work has evolved from measuring mainly navigational elements to measuring information on various thematic elements and establishing all information on seafloor terrain models. The large-scale comprehensive survey ship built for this purpose can simultaneously obtain water depth, sediment, gravity, magnetism, hydrology, meteorology and other data. Comprehensive automated measuring equipment has also been developed. For example, the Type 960 seafloor mapping system developed in the United States in 1978 can collect high-resolution bathymetry data, detect underwater obstacles such as sunken ships and downed aircraft, as well as bottom and shallow profile data, and simultaneously conduct seafloor mapping. Mapping and bathymetry, shallow seabed profiling. In addition to improving the content of ordinary nautical charts, the compilation of nautical charts also compiles various special nautical charts (such as Roland charts, Taika charts), seabed topographic maps, and various marine thematic maps (such as seabed sediment maps, oceanographic maps, etc.). Gravity maps, ocean magnetograms, ocean hydrographs), and various oceanographic atlases.