What are the key words for the application and development of marine surveying and mapping?

Abstract: Marine surveying and mapping is a branch of surveying and mapping. It is clear from the name of this branch that the object of marine surveying and mapping is the ocean. Marine surveying and mapping should not only obtain and display their respective positions, properties and forms, but also include their mutual relations and development changes, such as the relationship between waterways, reefs and lighthouses, the progress of harbor construction, seasonal changes of ocean currents and water temperatures, etc. It is also a basic and advanced work, and all marine activities are inseparable from marine surveying and mapping, especially in today's vigorous development and utilization of the ocean, the role of marine surveying and mapping is becoming more and more important. Because the important difference between marine and terrestrial natural phenomena lies in the ever-moving water distribution, its mapping method is obviously different from that of land, so the mapping of rivers and lakes in land waters is usually included in marine mapping.

Key words: early development of marine surveying and mapping, marine positioning, marine geodesy, underwater topographic survey, hydrographic survey, marine gravity field, magnetic field survey, aerial photogrammetry, satellite remote sensing survey, chart drawing and GPS positioning.

Marine surveying and mapping is a branch of surveying and mapping. It is clear from the name of this branch that the object of marine surveying and mapping is the ocean. Although the ocean is a Wang Yang, because the ocean is a synthesis of various elements, the objects of ocean mapping can be decomposed into various phenomena. These phenomena can be divided into two categories, namely, natural phenomena and human phenomena. Natural phenomena are all kinds of phenomena that exist objectively in nature, such as winding coast, undulating seabed, turbulent seawater and changeable ocean sky. In scientific terms, it is coastal and seabed topography, marine water literature and marine meteorology. They can also be decomposed into various elements, such as topography, material composition, geological structure, gravity anomaly and geomagnetic elements, reefs and other natural features, seawater temperature, salinity, density, transparency, water color, waves, currents, air and ocean temperature, pressure, wind, clouds, precipitation and marine resources. Humanistic phenomenon refers to the phenomenon formed by artificial construction, artificial installation or transformation, such as port facilities on the shore, such as docks, docks, mooring slips, wave prevention, etc. Various platforms and navigation AIDS in the sea, such as lighthouses, light boats and buoys. All kinds of man-made sunken objects, such as sunken ships, mines, aircraft wreckage, fishing nets, grids, etc., and specially set up port boundaries and military training areas. These phenomena include marine geography, marine geology, seawater literature and marine meteorology.

Marine surveying and mapping should not only obtain and display their respective positions, properties and forms, but also include their mutual relations and development changes, such as the relationship between waterways, reefs and lighthouses, the progress of harbor construction, seasonal changes of ocean currents and water temperatures, etc.

Because the important difference between marine and terrestrial natural phenomena lies in the ever-moving water distribution, its mapping method is obviously different from that of land, so the mapping of rivers and lakes in land waters is usually included in marine mapping.

Early development of marine surveying and mapping

Marine surveying and mapping can be roughly divided into three stages: ① Marine geophysical surveys, including marine seismic surveys and marine gravity surveys, began in the mid-1930s and 1950s. At this stage, the seabed topography map is drawn by using echo detection data to reveal the seabed topography; Obtaining all kinds of earth objects in the ocean crust by birefringence seismic method

Physical properties prove that there are significant differences between the oceanic crust and the continental crust. ② 1957 ~ 1970, International Geophysical Year (1957 ~ 1958), International Indian Ocean Expedition (1959 ~ 1965) and Upper Mantle Plan have been implemented. ③ Since 1970s, electronic technology and computer technology have been widely used in marine surveying and mapping.

Characteristics of marine survey

The object of marine investigation is the ocean. The biggest difference between the ocean and the land is that there is a turbulent water body with different depths above the seabed, which contains various organisms and inorganic substances with great differences.

Because of the existence of this water body, marine survey has the following characteristics obviously different from land survey in content, instruments and methods:

Because of this water body, the current marine survey can only be carried out on the sea surface or air, and it is difficult to move underwater. So there are no residential areas, no fixed road network and no vegetation except shallow sea areas. Therefore, the content of marine survey is mainly to detect submarine landforms, rocks, sunken ships and other features, but there are no elements such as water system, residential areas, road network and vegetation like land. Moreover, the submarine landform is much simpler than the land landform, with huge landform units and few traces of human activities. But this does not mean that marine survey is much simpler than land survey. On the contrary, marine survey is more difficult than land survey in many aspects.

First of all, water has the function of absorbing light, which produces refraction and reflection of light at different interfaces. It is difficult to use optical instruments commonly used in land surveys in marine surveys. Aerial photogrammetry and satellite remote sensing survey are limited to shallow sea areas with good seawater transparency. Acoustic instruments are mainly used for ocean exploration. However, the propagation speed of ultrasonic waves in seawater will change with the physical properties of seawater, such as salinity and temperature, which increases the difficulty of ocean exploration.

Secondly, it is difficult for naked eyes to see the bottom of the sea because of the blocking of water. In addition, traditional echo sounding can only be carried out along survey lines, and the measurement between survey lines is a blank area. The detailed survey of seabed topography requires an encrypted or full coverage multi-beam sounding system, which will greatly increase the survey time and funds.

Thirdly, it is very difficult to improve the accuracy of marine survey because of the variability of seawater.

Finally, at present, the carrier of marine survey is mainly ship, and the endurance of the ship is very limited. Moreover, the survey is limited by weather and sea conditions, and the global sea area is so vast that it takes a long time to investigate the global sea area in detail.

On the chart, the land-sea boundary at the average sea level is not regarded as the coastline. Because this line was submerged in the water at high tide, although it was exposed to the water at low tide, its traces were washed away by seawater at high tide, so it was difficult to determine its position on site. Some features on the coastline, such as headlands and special colors, are important targets for determining the position and direction of ships when sailing. It is very useful for navigation to determine the location with obvious traces as coastline. According to the analysis and research, there are often obvious traces of the land-sea boundary at the high tide of the average spring tide. For example, on steep river banks, there are generally traces of seawater erosion; Vegetation-covered coast

There's too much to answer.