碩士 / 國立中山大學 / 海洋環境及工程學系研究所 / 101 / When divers conduct underwater operations, supervisors at the surface are often unable to accurately collect behavior information of the divers predominate the tendency. The established information for underwater cases mostly are based on diver’s dictation. In fact, supervisors at the surface have no way of justify whether the target verified by divers is the target under investigation. Due to the existence of turbidity, light attenuates quickly in the water within an effective distance of meters or even cent-meters. Therefore, optical instruments are unable to effectively observe the diver''s movements. On the other hand, based on good penetrating and large area coverage characteristics of sound pulse, acoustical instruments such as scanning sonar has the potential in monitoring underwater environment and in detecting divers and their behavior. Based on searching purposes, operation parameters of the scanning sonar can be adjusted to meet the needs of field operations.
This research was conducted by collecting and analyzing data collected at two cases, i.e., drowned person rescue mission at Shuang-Yuan Bridge and divers’ renewal training at Yen-Pu port. The initial purpose at Shuang-Yuan Bridge case was searching for drowned human body. The high image resolution is needed. So the scanning range was set to 5 meters with frequency at 1 MHz. As for detecting and monitoring divers’ activity, the scanning range was set to 10, 30, and 50 meters with frequency at 675 kHz in order to satisfy underwater surveillance and divers’ route tracking.
For economizing manpower and avoiding inaccurate judgments, this study developed an automatic sonar image processing system by using grey level co-occurrence matrix(GLCM) and Bayesian classification to identify mobile target in the sonar imagery. To improve the successfully detection rate of the processing system, a mobile target intensifying method was adopted. In this procedure, both static and mobile target were identified and mobile target was intensified by the removal of the static background.
The accomplishment of this study included：
(1) The scanning sonar used in this research can effectively detect the presence of divers at range setting of 50 meters.
(2) During detection processes, both information regarding underwater environment and divers’ activities were effectively collected.
(3) After a mobile target intensification procedure, the mobile target in the collected sonar imagery can be effectively identified through an automatic procedure dominated by GLCM and Bayesian classification.
(4) Mobile target quantitative information was collected by a region growing procedure. This quantitative information could be used as a criterion in identification of the existence or non-existence of mobile target, in tracking divers’ movement and in quantifying divers’ effective searching area.
At this stage, imagery collection by the scanning sonar and target identification through an automatic procedure were conducted separately. The application potential of this research could be greatly improved by the combination of these two major components together in time sequence. A plausible application is in the field of underwater invader detection and identification.
| Identifer | oai:union.ndltd.org:TW/101NSYS5282037 |
| Date | January 2013 |
| Creators | Po-li Chuang, 莊博理 |
| Contributors | W.M. Tian, 田文敏 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 134 |
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