Factors Controlling Accuracy of Multi-Beam Sonar Bathymetrical Survey in the Vicinity of Nearshore Area
Date Issued
2007
Date
2007
Author(s)
Lee, Chien-Feng
DOI
zh-TW
Abstract
Impact conditions for the factors affecting multi-beam sonar sounding are different in the vicinity of nearshore area (shallower than 10 meters) and the deep water area (deeper than 100 meters). For instance, if the dynamic motion sensor of the system was not located on ship's gravity center, the measurements could not be true heave values induced by the heave motion only. Thus, if the heave motion was compensated without going through properly correction procedure, the quality of the multi-beam sonar survey data will deteriorate as the water gets shallower. In addition, the ability of patch test is feckless if it was conducted in the area where the water depth is too small; as a result.. to satisfy precision requirements for the multi-beam sonar survey, roll offset angle is the only parameter needed to attend to its accuracy. As to pitch and yaw offset angles, their influence to data quality becomes insignificant. Nearshore of estuary area, the river and sea water can be stratified by tidal motions, such that a distinct top layer is present in the acoustic velocity profile. Therefore, several acoustic velocity profiles shall be obtained in different time and area to make the correction to the refraction of ray path. The last factor is from tide correction effect, the error correction can not be identified easily as survey conducting in the area where water depths are small. This is because that when the track lines are short such that surveying interval to the next track-line is separated at several minutes away, we will lose the crud to identify the error caused by ill correction that induces track-line effect.
Subjects
多音束測深系統
近濱區
起伏值
疊合測試
聲速校正
潮位修正
multi-beam sonar system
nearshore
heave
patch test
sound velocity correction
tide level correction
Type
thesis
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