Data Fusion Technique for Multibeam Echosoundings

On the basis of an analysis of the error sources in multibeam echosounding system,a data processing method for compensating systematic errors in multibeam survey is proposed.In order to improve the accuracy of overall swath,a data fusion technique using single beam survey data as control information for single beam and multibeam echosounding is then presented.Some questions involved in solving the adjustment problem,such as its feasibility and the numerical stability,are discussed in detail,and a two_step adjustment method is suggested.Finally,a practical survey data set is used as a case study to prove the efficiency and reliability of the proposed methods.

Rifting characteristics of eastern subbasin of South China Sea and its spreading pattern

With processing and interpretation of 25 000 km full-coverage multibeam swath data from the eastern South China Sea, it is found that NE-trending and NW-trending linear morphological featuressuch as scarps, horsts and grabens, govem the central part (14°～ 17° N) of eastern subbasin.Compared with reflection seismic profiles, these NE-trending linear morpho-structures are considered to be the representation of basement structures on seabed and can be divided into three linear structural zones. The trend of the central zone is NE45°～50° occurring around extinct spreading center, the trend of the second zone is NE70°～78° on both sides of the central one and the trend of the third zone is about NE60° just on the north of the second one. These three NE-trending linear zones are formed in late-stage NW-SE-trending seafloor spreading of the eastern subbasin along NW-trending linear faults, and respectively correspond to three spreading episodes: 17.0～19.0 Ma (5d-5e), 19.0～21.0 Ma (5e-6a) and 21.0～24.2 Ma (6a-6c) based on the contrast of morpho-structures to magnetic lineation anomalies.

An Integrated Approach to Hydrographic Surveying of Large Reservoirs—Application to Tarbela Reservoir in Pakistan

Hydrographic surveying in reservoirs is a key activity in order to collect data for a variety of purposes like estimation of storage capacity, rate and pattern of sediment deposition, movement of underwater sediment delta and reservoir routing, etc. These parameters play a pivotal role in any planning, management and operation activity of the reservoirs. Traditional approaches to perform hydrographic surveying in Indus Basin are time consuming, laborious, comparatively inaccurate and costly. As water resources are under immense pressure due to a variety of factors, such inefficient methods are not acceptable for efficient water management. In this study, an integrated approach for hydrographic surveying is introduced and evaluated in terms of its efficiency in comparison with the traditional methods of hydrographic surveying. The approach develops an integrated environment of hydrographic surveying comprising human, hardware and software. The process of surveying starts from in-house planning using specialized geo-spatial softwares. Then, on site a combination of computer hardware, echosounder, differential global positioning system (DGPS), survey vessel and survey crew is made. Post-processing is performed after conducting a survey in order to improve quality of data by filtering errors and producing the end product like reservoir underwater terrain, development of reservoir stage-area and stage-storage relationships, etc. The study was applied to Tarbela Reservoir, Pakistan.