Research On Mosaic Technique Of Multi_beam Swath Bathymeter

Multi-beam Swath Bathymeter is a kind of newly developed advanced seafloor surveying equipment. It fits especially for mapping of large area of seafloor because of its high efficiency, high accuracy and fine terrain resolution. The main purpose of seafloor surveying is to obtain digital sea charts, which are developed by means of mosaic technique under the constraints of hydrographic surveying principles. Therefore, mosaic technique is of fundamental importance in surveying processes.Applying the information extracted from numerous hydrographic data of field trials collected by H/HCS-017, the first set of Multi-beam Swath Bathymeter developed in China, a series of mosaic techniques have been carefully studied in this thesis, including digital terrain model building, statistical error analyzing, hydrographic data mosaicking as well as tides correction and projection of the Earth coordinates. Finally, standard digital sea-charts and three dimensional seafloor images are successfully developed that are consistent with hydrographic surveying principles.Making full use of the correlated space information of multi-beam bathymetric data, the author put forward a method of Gaussian surface approximation to build the grid net of regular Digital Terrain Model (DTM) of surveyed seafloor, which is more accurate than other approximation methods. The generation of standard isolines is a very complex and difficult job in mosaicking process. The author proposed a new method called gliding adaptive smoothing in this thesis, which avoided the crossing of isolines efficiently and removed corners of isolines as well. These phenomenons usually occur unexpectedly in conventional processing. Besides, based on the computer graphic techniques, the author also studied the nature of subject projection, texture and lightning to generate three-dimensional vision of surveyed seafloor.On base of the theory studied, the author developed a package of applied mosaicking software, using Microsoft Visual C++6.0 and OpenGL graphic techniques. The software was tested with field trial data of H/HCS-017. Digital sea charts generated by the software are satisfactory and meet the hydrographic surveying principles.