Progress and Prospects of Hydrographic Surveying Technology ’In China
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Progress and Prospects of Hydrographic Surveying Technology ’in China By Huang Motao, Zhai Guojun, Ouyang Yongzhong, Liu Yanchun and Lu Xiuping, Tianjin Institute of Hydrographic Surveying and Charting, P.R. of China, China During the last decade, significant ity. In recent years, with the improve advances have been made in the study ment and development of computer of hydrographic surveying technology in technology and information acquisition, China. This paper gives an outline of an outstanding change has also recent progress in the fields of survey occurred in the branch of marine sur equipment, information acquisition, veying. Besides traditional hydrogra data processing, data management, phy, many new branches of marine sur basic survey theory and their applica vey, such as marine control survey, tions. The future development trends marine engineering survey, seabed are discussed and presented. topography, marine gravity and marine magnetism survey, have shown their value. Three areas of technology, i.e., Introduction airborne laser hydrography, shallow water multibeam depth echo sounding With the development of modern com and digital side scan sonar, are puters, as well as space and communi thought to be the newest technology cation technology, significant changes for shallow water hydrographic surveys have taken place in surveying and owing to their high speed and high res mapping science and techniques, from olution. The application of this new its theory to its application. As early as equipment has resulted in an impor 1990, the International Union of Sur tant change from point and line survey veying and Mapping (IUSM), gave a new mode to swath measurement. Breaking definition to surveying and mapping. through the traditional limit of time and Namely, that, it is a branch of science, space, marine surveying has at last engineering and technology, which advanced to a new stage where digital deals with the acquisition, measure survey methodology, computer technol ment, processing, analysis, explana ogy and 3S (GPS, GIS, RS) technology tion, description, distribution, usage plays an important role. In the past few and evaluation of geo-spatial informa years, significant progress has been tion. Marine surveying is an essential made in the study of hydrographic sur part of surveying and mapping science vey technology in China. They are and technology, and its major mission briefly summarised in the following: is to measure and describe the para (1) There is an increase in the different meters of ocean geometry and physic. types of survey equipment available. Its purpose is to provide information on (2) In data acquisition and collection, ocean space, required for human activ there has been a change from ana- logue recording to digital and automatic recording. beam echosounding system was developed suc (3) In data processing, a change from manual pro cessfully in 1997 by Haerbin Shipping Industry Uni cessing to automation has occurred. versity and deployed in the following year. The (4) Standardisation and the development of net H/HCS-017 echosounder comprises a transducer working have been emphasized in data man array, a transmitter subsystem, a receiver subsys agement systems. tem including beamformer and special digital signal (5) More attention has been turned to application processors, a bottom detector unit, and an operator in the study of basic survey theory. unit for data transfer with external interfaces. The complete mapping system also includes the addi tional units: (1) vessel motion sensor; (2) position Progress in Survey Equipment ing system; (3) sound speed sensor; (4) postpro cessing system. The H/HCS-017 system operates Multibeam Depth Echosounding Technique at a frequency of 45 kHz. It has 48 beams with a The multibeam echosounder is a relatively new type beamwidth of 2° across-track and 3° along-track. of hydrographic survey system with high accuracy, The system is designed to operate in water depths high resolution and high efficiency. It is designed for from 10 to 1000 m below the transducer. It has a mapping 100% of the seafloor. In recent years, swath width of up to 4 times the water depth. The multibeam echosounding systems, especially shal- swath angle is 120° degrees. The H/HCS-017 sys low-water mapping systems, have been developing tem is capable of meeting the present IHO stan rapidly for various applications, from hydrographic dards. The successful development of the H/HCS- surveying to underwater inspection, from mine hunt 017 system has shown that China had achieved a ing to shoreline studies. Multibeam echosounders great step forward in the study of hydrographic sur are quite different from conventional single beam vey equipment (Chen, 1999; Zhu, 1999). echosounders, in their principles of operation and According to the need for modern hydrographic sur also in the way they are constructed. Unlike conven vey development, the International Hydrographic tional single beam echosounders, the multibeam Organization (IHO) promulgated a new version of the depth echosounder is a complex survey system in hydrographic standard, namely IHO S-44, at the which multi-sensors are used. Seabed topographic International Hydrographic Conference in Monaco in survey technology has made great progress owing to September 1994. 100% coverage of the seafloor is the development of the multibeam depth required in the new edition of the IHO S-44 standard echosounder (Mccaffrey, 1981; Tyce, 1986; Atanu for the higher orders of hydrographic surveying. In and Saxena, 1999; Li, 1999). order to meet the requirements of different users, In order to meet the requirements of different the manufacturers of multibeam equipment are mak marine activities, China began to introduce multi ing a great effort to develop sounding technology for beam depth sounding systems from abroad in the full ocean depth, higher resolution, higher accuracy, early 1990’s. To date, many types of such system and modular and integrated concept design (Huang, exist, including the new generation products, which Zhai, Ouyang, et al., 2000). It should be noted that have been extensively taken into use in marine sci during the last decade multibeam technology has ence research, marine resource and environment improved technically, the price level has dropped, investigation, hydrographic surveying, marine engi and the system electronics has been made much neering projects, port maintenance, monitoring of more compact. It can be said that multibeam tech geologic catostrophy investigation and under water nology has now advanced to a stage where many archaeology. They are playing an important role in users will benefit from taking it into use. The main the sustainable development of the economy and motivation for going from single beam echo sound society of China. Since the middle 1980’s, China ing to multibeam echo sounding is the capability to has been involved in the study of multibeam produce maps of much higher quality and with much echosounding systems. During that period, only a more details than previously, with a high productivity prototype was developed and some tests have been rate and reduced cost per area unit. Although the made. No practical products were developed due to capital cost of multibeam echo sounders is higher technical and funding reasons. In the early 1990’s, than for conventional survey echo sounders, they China began to invest again in research of multi produce maps at lower cost than before, and with beam echosounding systems. The H/HCS-017 multi better quality. The quality of the maps is higher, not because each sounding is more accurate, but propose that the manufacturers of multibeam because of the dense sounding pattern. The dense equipment and other organisations consider the soundings reveal aii the significant underwater fea need for uniformity of data format and post-pro tures, and eliminate the large errors generated by cessing software in order to get a rapid develop having to guess (or interpolate) what the seafloor is ment for the multibeam technology. like between the survey lines. It is because of these facts that more and more hydrographic institutions Airborne Laser Sounding Technique and other organisations are considering replace The application of lasers to hydrography was pio ment of their existing equipment for mapping the neered in Australia during the 1970’s and 1980’s shallow seabed by the new generation of multibeam by the Australian Defence Science and Technology systems. Now on the international market of multi Organisation. This work opened up a new field for beam echo sounder, almost every manufacturer hydrographic survey, i.e., the airborne laser sound claims that its product adheres to the most accurate ing technology (Wehr and Lohr, 1999; Baltsavias, IHO standards for hydrographic surveys. That is to 1999).Airborne laser depth sounding (lidar bathy say that the new generation of equipment is ideal for metry) is thought now to be one of the most prom hydrographic surveying today. The trend in this field ising techniques for rapid and high density sound- is toward making the systems of lighter weight so ing of shallow waters because of its high mobility, that they can be deployed on smaller vessels and cost effectiveness and easy administration due to capable of collecting accurate data at higher speed. a low need of manpower (Andrew, et al., 1998). In It should be noted that, with the development of China, work for testing the principle of operation for modern digital computer technology and other pow airborne laser depth sounding has taken place erful techniques, the hardware configuration of the since the middle 1980’s, but did not advance to a new generation mutibeam echo sounder has now practical stage until the middle 1990’s (Tang, at last advanced to a stable stage. In many coun 1998; Guan, et al., 1999). The Shanghai Institute tries multibeam survey equipment is now the stan of Precise Optical Mechanism has been involved in dard tool for seabed mapping .