| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 99 === Multi-beam echo sounders are normally equipped with kinds of Peripheral devices for the measurements. However due to the complexity of supporting devices, and massive amount of water depth data, a considerable amount of Irreversible artifacts will occur. This study uses Cross Over Check method to survey error distribution that caused by different means, and attempt to correct the discrepancies. In the problem of positioning error, GPS measurements have poor quality than the DGPS (differential GPS) and deviation of the errors shows time dependence. Therefore, there is no way to apply a constant correction value to fix the problem. Moreover, it is estimated that the GPS solutions can be used when the sounding area with the relief of the slope less than 1.3 degree. When the transducer is installed with more than 1 roll offset angle, bathymetry accuracy will easily fail to satisfy the IHO level when seabed is 25m deep. Pitch offset angle will cause the error shift towards positive value, but the occurrence is slight when seabed is shallow and flat. Checking the errors of every track can be realized with check line crossing with track, check line crossing with all locations of sound beam footprints. Direction of the cross over lines shall be perpendicular with the azimuth of survey tracks, such that check lines can be crossing inner and outer beams of the survey lines at almost equal proportion. Under this condition, the output value to judge the quality of bathymetry can be accepted statistically.
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