(Guangzhou Marine Geological Survey Guangzhou 5 10760)
Brief introduction of the first author: Feast, male, born in 1973, engineer, mainly engaged in marine geological survey, participated in 105- 15 marine survey, natural gas hydrate resource survey, and participated in 863, 126 and marine research.
Modern communication technologies such as acoustic communication technology, ADSL communication technology, satellite communication technology and local area network communication technology are widely used in marine geological survey today. This paper introduces the principles of several main modern communication technologies and their application examples.
Modern communication technology, marine geological survey, acoustic communication technology, satellite communication technology, ADSL communication technology.
1 preface
Modern marine geological survey has increasingly become a comprehensive application platform of various high technologies, such as marine (underwater) equipment and sensors. ), land (survey ship, working platform, etc. ) and air (GPS positioning, satellite communication, etc. ). Especially with the rapid development of satellite communication technology, mobile communication technology, network communication technology and computer information technology, various modern communication technologies have been widely used in marine geological survey (Figure 1
Figure 1 Schematic Diagram of Communication Technology Application
Figure 1 Schematic diagram of communication technology App
2 Application in marine geological survey
Modern communication technologies widely used in marine geological survey today include acoustic communication technology, ADSL communication technology, satellite communication technology, local area network communication technology and radio communication technology.
2. 1 Application of acoustic communication technology
The ocean is a mysterious place. In seawater, electromagnetic waves decay quickly and light is easily absorbed or scattered, so it is difficult for radio and its optical communication technology to be widely used in seawater as on land. With the development of modern science and technology and the need of human progress, the propagation characteristics of sound waves in water have gradually formed a new underwater acoustic communication technology. Underwater acoustic communication is a high-tech communication technology, and the working process of the whole system is complicated, which requires a series of signal conversion. Convert data, characters, sounds, images and other information into electrical signals, then digitize the information through an encoder, and then convert the electrical signals into acoustic signals through a transducer. Sound signals are transmitted to the receiving transducer through the water medium, where they are converted into electrical signals, and the decoder compiles digital information into data, sounds, words and pictures.
Acoustic communication technology is the main communication means of cable-free marine survey geological equipment. At present, the typical equipment used for acoustic communication or control on marine geological survey vessels in China are: multi-beam (seabed topography survey) equipment (such as seabeam 212, SIMRAD EM-3000, EM-950 and other multi-beam systems) and sounding equipment (such as SOUND2 10). Ultra-short baseline and long baseline underwater positioning equipment (such as NAUTRIX USBL system), various typical sonar equipment, underwater acoustic communication modems, PINGER, etc. All transmit and receive acoustic signals modulated with data signals and control signals through acoustic transmitters and receivers (hydrophones), acoustic arrays, and the like. So as to carry out communication and data acquisition and control.
The speed of sound wave propagation in seawater is a function of temperature, salinity and pressure. Generally, Wilson's empirical formula is used to calculate the speed of sound, that is, c =1449.14+△ CT △ CS △ CP △ CSTP.
In the formula, 1449. 14 is a constant, which represents the sound velocity of seawater at 0℃ and salinity of 35.00 at one atmospheric pressure.
△CT represents the sound velocity correction caused by temperature change:
△CT = 4.572 1T-4.4532 @ 10-2 T2-2.6045 @ 10-4 T3+7.985 @ 10-6 T4
△CS represents the sound velocity correction caused by salinity change;
△CS = 1.3980(S-35)+ 1.692 @ 10-3(S-35)2
△CP represents the sound velocity correction caused by the change of seawater pressure:
△CP = 1.60272 @ 10- 1P+ 1.0268 @ 10-5 p2+3.52 16 @ 10-9 P3-3.3603 @ 10- 12 P4
△CSTP represents the sound velocity correction value generated when salinity, temperature and pressure change simultaneously.
In the above formula, c is the speed of sound; T is temperature; P is the seawater pressure; S is salinity; Z is depth.
When sound wave propagates in seawater, it will be affected by many factors, not only the working frequency, but also the reflection and refraction caused by the temperature, salinity, various noises and various obstacles of seawater. Due to the noise interference caused by waves, fish and ships in the ocean, sound waves propagate in seawater and form "multi-channel interference signals" at the same time. In addition, the absorption of sound waves by seawater will lead to the ambiguity of received signals, and the transmission efficiency and quality will be high. With the development of science and technology, new technologies such as frequency hopping communication and pseudo-random code modulation are used to solve the noise interference and "multipath interference signal" in underwater acoustic communication. However, the speed of sound wave in water is less than1/200,000 of the speed of light, and the transmission rate of sound signal in water is low. Coupled with the scattering, transmission loss and echo interference of sound waves in water, the underwater acoustic communication distance is only about 10km.
2.2 ADSL communication technology application
ADSL (Asymmetric Digital Subscriber Line) technology, namely asymmetric digital subscriber loop technology, is one of the most widely used Internet access technologies for XDSL series copper cable users. It transmits data, voice and video signals at high speed through ordinary telephone copper wire. The uplink adopts FSK (frequency shift keying) technology, and the downlink adopts DMT (discrete multi-tone modulation) technology or CAP (carrier-free amplitude/phase modulation) technology to provide users with asymmetric transmission rate (bandwidth). Its downlink rate is between 2.048 MB/s-8. 19mb/s, and its uplink rate is about 640 KB/s. ADSL system is mainly composed of local office module and remote module. With the development of technology, it has gradually become a more convenient broadband access technology. ADSL system is formed by adding an ADSL local device and a remote device at both ends of a pair of ordinary copper wires. ADSL modem is mainly composed of analog front-end for D/A conversion, digital signal processor (DSP) for modulation/demodulation, and digital interface for reducing transmission power and transmission error of digital signal and realizing error correction by "trellis coding" and "interleaving processing" (Walter, 2000). ADSL is an advanced access technology and has the reputation of "network express". Because of its high speed, wide bandwidth, excellent performance and convenient installation, it has become a brand-new and efficient communication technology after MODEM and ISDN.
With the development of marine technology, ADSL technology has been widely used in marine geological survey equipment, such as ROV system and submarine video acquisition system. The following is an example of "Deep-sea Color Digital Camera System" (863 Project, developed by Guangzhou Marine Geological Survey). The system block diagram is shown in Figure 2.
Fig. 2 Structural block diagram of seabed observation system
Fig. 2 Structural block diagram of seabed observation system
"Deep-sea color digital camera system" uses the original CTD armored steel cable as the transmission medium, and ADSL modems are used in the deck control unit and underwater unit respectively. ADSL communication technology is used to realize network interconnection, video transmission and acquisition control. Due to the influence of tensile strength, water tightness and high voltage resistance, the requirements for armored cables are very high. The traditional armored cable has low bandwidth, so it can't transmit high-fidelity video images on the seabed in real time without delay, and can only compress the images with loss. Now the latest submarine observation and video acquisition system begins to use armored optical cable as transmission medium, which greatly expands its transmission bandwidth, improves the real-time and fidelity of submarine observation, and makes the submarine video observation and acquisition technology move forward to photoelectric communication technology.
2.3 Application of satellite communication technology
With the development of space satellite communication technology, satellite communication has been widely used in marine geological survey, especially GPS satellite positioning and satellite meteorology.
GPS (Global Positioning System) is a satellite-based radio navigation system, which can provide three-dimensional navigation, positioning and timing for users in aviation, aerospace, land and ocean. GPS consists of satellite constellation (space part), ground monitoring system (ground control part) and GPS signal receiver (user equipment part). The space part of GPS consists of 24 working GPS satellites, which together form a constellation of GPS satellites, of which 2 1 is a navigation satellite and 3 are active backup satellites. These 24 satellites are distributed in six orbits around the earth with an inclination of 55. The average height of the satellite to the earth's surface is 20200km, and its operating period is about 12 sidereal time. At least four satellites can be observed anywhere on the earth at any time. Every GPS working satellite will send out navigation and positioning signals. GPS users use these signals to work. Make three circles with three satellites with known positions as the center and the distance from the measured point to the satellite as the radius. The intersection of these three circles is the position of the measured point. In GPS system, the position of the measured point is determined according to the three satellites running in the air and the distance between these satellites and the measured point. Global satellite positioning and navigation system adopts multi-satellite high orbit ranging system. After the GPS receiver receives signals from more than three satellites at the same time, the user's position can be determined by the intersection of the three satellites and the user's three equidistant spheres. Through the observation of four satellites, it is also possible to time and correct the ranging error with the clock error correction value (Xu Shaoquan et al., 2004). The system has the advantages of global continuous coverage, high positioning accuracy, passive all-weather visibility observation, simple operation and strong anti-interference ability, which makes its application field expand continuously. Although the US military has adopted selective availability and anti-deception technology for strategic purposes, the current phase observation method can bypass the influence of SA. Most human errors are eliminated, and its application is not limited to the military use of navigation and positioning, but also can be used in geodesy, geodynamics, atmospheric science, disaster monitoring and so on.
In marine geological survey, GPS (or DGPS) satellite communication positioning is often used, and the coordinates of each station are located in real time through GPS satellite. The navigation GPS receiver receives the GPS satellite signal, and then navigates and locates the ship according to the measurement projection method. There are different types of GPS receivers, such as SECEL GPS receiver, LGBX-PRO GPS receiver, SF2050 GPS receiver, etc. Their accuracy indicators are also different.
During the marine geological survey, the survey ship also receives meteorological satellite signals every day, and judges the meteorological situation of the operation area in the next 24 hours according to the meteorological information displayed on the satellite cloud image (such as the generation and general trend of typhoon, low pressure and high pressure), so as to dynamically arrange the station survey operation.
With the development of Internet technology, it is also possible to send and receive emails and browse the news on the Internet in real time on the survey ship, but at present, the uplink and downlink speed of satellite channels is relatively slow and the cost is high.
2.4 Application of LAN communication technology
The comprehensive survey of marine geology includes DGPS navigation and positioning survey, geological sampling and description, chemical testing and analysis, multi-beam and underwater acoustic survey, etc. We should not only collect data, but also process, interpret, analyze and study it. All kinds of data are independent and closely combined with each other, so it is necessary to comprehensively analyze and utilize all kinds of data in the investigation, so it is necessary to share all kinds of professional data.
In modern marine geological survey, paperless digital office and network office in the field are increasingly becoming new office methods, which can not only save costs, but also improve efficiency and reduce errors. Secondly, the network sharing of ship position information, state, materials and meteorological information can not only provide decision-making reference for the chief scientist's scientific deployment, but also better serve the captain's overall command of the ship; Therefore, with the development of information technology, wired LAN communication technology and wireless LAN communication technology for ship survey have been widely used. Taking the "Ocean No.4" scientific research ship of marine comprehensive geological survey as an example, LAN communication technology has been well applied in comprehensive information collection and field office. Fig. 3 is the communication module diagram of "Ocean 4" LAN.
Figure 3 LAN communication module diagram of "Ocean IV" scientific research ship
Figure 3 LAN communication module diagram of Haiyang No.4 ship
2.5 Application of traditional radio communication technology
In modern marine geological survey, traditional radio communication technologies, such as walkie-talkie and single sideband, are still used.
3 Conclusion
Modern communication technology has been widely used in marine geological resources survey, but due to many objective conditions, many modern communication technologies that have been used on land can not be used in the vast ocean. The next generation space network architecture is being developed. This new architecture will ensure the interoperability between the ground (including land, ocean and atmosphere) and satellite networks by using internet protocols, and use satellites for communication interconnection, which will completely change the way of data storage, transmission and use. Satellite-based IP communication network can extend its services to users anywhere in the world on a global scale. We look forward to the coming Next Generation Network (NGN), Next Generation Telecommunication Network (NGT), Next Generation Internet (NGI) and Next Generation Wireless Mobile Communication Network (3G, B3G, 4G) to provide good technical services for maritime communication based on satellite IP network platform. We are convinced that scientists' unremitting efforts to "one world, one network" are no longer a dream, and the ground and space will jointly form a seamless satellite communication.
Reference materials and materials
Technical Manual of Submarine Camera, Guangzhou Marine Geological Survey.
Guangzhou marine geological survey, seabeam2 1 12 technical manual.
Edited by Walter Golsky. Liu Yong et al., 2000. ADSL and ADSL technology, Beijing: People's Posts and Telecommunications Press.
Xu Shaoquan, Zhang Huahai, Yang Zhiqiang and Wang Zemin. 2004. Principle and application of GPS measurement (revised edition). Wuhan: Wuhan University Press.
Application of modern communication technology in marine geological survey
Feast civilization
(Guangzhou Marine Geological Survey, Guangzhou, 5 10760)
Abstract: Communication technologies such as voice communication technology. Network communication technology. ADSL communication technology and satellite communication technology are more and more used in marine geological survey. This paper briefly introduces the principles of these communication technologies and their applications in different survey equipment and methods.
Keywords: communication technology. Acoustic communication technology of marine geological survey satellite communication technology. ADSL communication technology.