Taiwan is surrounded by ocean, we expect through the underwater survey could make us know more about the marine resources, history and culture and understand how to use the natural resource well. The purpose of this paper is to investigate the survey strategy for marine archaeology using modern underwater survey and identification instruments and techniques on Peng-Hu underwater cultural site survey. The survey process can be roughly divided into three stages, preliminary and comprehensive survey (PCS), double-check and localization survey (DLS), and precise and identification survey (PIS) respectively. The objective of PCS is not to miss any possible target. The major equipments of the underwater engineering including marine magnetometer, the subbottom profiler, and the side-scan sonar are deployed simultaneously. After the comparisons and analysis of the images from various instruments obtained from PCS and DLS, the PIS will obtain the direct photo viewing of the targets using remotely-operated vehicle (ROV) or divers. This strategy has been conducted firstly in Kaohsiung Sizihwan bay Marine Test Field and Kaohsiung Cross-Harbor Tunnels as the preliminary. Then move to Peng-Hu Sea Area for the underwater archaeology survey which is authorized by Acdemia Sinica from April 2008 to June 2009. From the result, the megnetometer can help sonar to identify the target more specifically, especially for the sediment. It brings better result than side-scan sonar and multi-beam echo sounder which can only search the target on seabed and can search broader area than subbottom profiler. Therefor, magnetomator is an essential equipment for underwater archology.

Magnetic survey is a common geophysical exploration technique. By measuring the magnetic field strength at specific area, the characteristics and physical meaning of the target can be obtained through the analysis of the Earth's magnetic field anomalies within a stratigraphic zone or archaeological sites. In recent years, the marine magnetometer is employed to conduct underwater archaeological expedition at surrounding waters of Taiwan for ancient shipwrecks researching. The purpose of this study is to understand the relationship between the magnetic anomalies with the magnetic object via the various signal processing methods, included the calculation horizontal and vertical derivatives using fast Fourier transform (FFT) to eliminate the regional magnetic influence and gain the anomalies characteristics of the target itself, as well as highlight the location and boundaries of the magnetic source through the analytical signal. In addition, the Euler deconvolution implements as a tool for magnetic source inversion. The theory of Euler deconvolution was first proposed by Thompson (1982), this method is able to detect the magnetic source and estimate its locations by choosing the suitable structural index. Hsu (2002) proposed the enhanced Euler deconvolution, which is a combined inversion for structural index and source location through the use of the vertical derivative of measured data.In this study, we first generate various anomalies as testing models which are correspond with different geometric shape of magnetic source, the position and structural index for model is inversed by enhanced Euler deconvolution in both 2D and 3D.Moreover, the experiment was planned at offshore of Dalinpu in Kaohsiung, we took the CPC's pipelines as investigation objects which were buried under the seabed, than compare with sub-bottom profiler data to assess the feasibility of this method for underwater exploring applications.The most estimated results in 2D are correspond to the theory, but it does not have significant results in 3D due to the lack of observed data for the whole surface.In general, this method is concise and fast, it is fit for interpreting the magnetic data for exploring the underwater object.

The application of underwater search and identification technology has been widely used in the underwater engineering. There are two major fields in this thesis: monitoring of underwater structures and analysis of upper-layer geological properties of seabed. The former focus on the cooperation of these three major equipments: sidescan sonar, sub-bottom profiler, and marine magnetometer to improve the ability of identification. The latter analyzes the image displayed by the sub-bottom profiler to set up the data base of different environments and equipments. Finally, it is illustrated that the difference between the actual position and the data position exists in equipment with a tow fish style to refine the search technology and predict the real position. This thesis will demonstrate the monitoring of underwater structures, analysis of upper-layer geological properties of seabed, and the position error of underwater targets to discuss and improve the capability of the underwater search and identification technology.