- 學位論文
近濱區外淺水海域多音束地形測量的影響因素探討
Factors Controlling Accuracy of Multi-Beam Sonar Bathymetrical Survey in the Vicinity of Nearshore Area
摘要
多音束測深系統在近濱區外淺水海域（深度在10公尺以內的區域）與在深水環境（上百公尺的深度）中，影響因素上有著不同程度的要求條件。例如，動態感應器如不架設在船重心位置，所測量的起伏值並非真正的起伏量；因此引用錯誤的起伏值，水深愈淺對多音束資料的影響愈大。另外，因為疊合測試在水深愈淺處進行其效率愈低，為滿足對多音束測深的精度要求，只有橫搖偏差角需特別注意其精準度，但對於縱搖偏差角與航偏偏差角，其精度對資料品質影響不大。在河口之近濱區施測，因受漲退潮影響，河水和海水有分層現象，造成聲速分層的厚度不同，因此需要不同時間的聲速剖面資料來進行聲速校正，這是因為音波會有不同的折射路徑。最後，潮位修正的錯誤不容易在淺水資料中被認出來。這是因為潮位修正發生錯誤時，會造成在資料疊合或相鄰的區域形成不等量誤差的航線效應。若航線愈短，時間間隔愈短，誤差量差值愈小，航線效應會愈不明顯，喪失對潮位修正錯誤時的判斷依據。
並列摘要
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.