Henry M. Manik

Seabed Identification and Characterization Using Sonar

Application of sonar technologies to bottom acoustics study has made significant advances over recent decades. The sonar systems evolved from the simple analog single-beam and single-frequency systems to more sophisticated digital ones. In this paper, a quantified sonar system was applied to detect and quantify the bottom echoes. The increasing of mean diameter is accompanied by a higher backscattering strength. From this study, identification and characterization using sonar is possible.

Measuring acoustic backscattering strength of underwater target using high frequency sonar

A basic designing method of high frequency sonar transmitting-receiving system for measuring acoustic backscattering strength is developed. The method is experimentally examined using the laboratory and ocean data obtained by sonar instrument. The results show that the experimentally observed the backscattering of underwater target is different. Sand bottom has a highest backscattering than mud bottom, fish, and seagrass. Discrimination of fish, seagrass, and bottom type using sonar signal processing is possible.

Estimation of suspended sediment concentration from Acoustic Doppler Current Profiler (ADCP) instrument: A case study of Lembeh Strait, North Sulawesi

Measurement of suspended sediment concentration (SSC) is one of the parameters needed to determine the characteristics of sediment transport. However, the measurement of SSC nowadays still uses conventional technique and it has limitations; especially in temporal resolution. With advanced technology, the measurement can use hydroacoustic technology such as Acoustic Doppler Current Profiler (ADCP). ADCP measures the intensity of backscatter as echo intensity unit from sediment particles. The frequency of ADCP used in this study was 400 kHz. The samples were measured and collected from Lembeh Strait, North Sulawesi. The highest concentration of suspended sediment was 98.89 mg L-1 and the lowest was 45.20 mg L-1. Time series data showed the tidal condition affected the SSC. From the research, we also made correction from sound signal losses effect such as spherical spreading and sound absorption to get more accurate results by eliminating these parameters in echo intensity data. Simple linear regression analysis at echo intensity measured from ADCP to direct measurement of SSC was performed to obtain the estimation of the SSC. The comparison result of estimation of SSC from ADCP measurements and SSC from laboratory analyses was insignificantly different based on t-test statistical analysis with 95% confidence interval percentage.

Quantification and Analysis of Suspended Sediments Concentration Using Mobile and Static Acoustic Doppler Current Profiler Instruments

The application of Acoustic Doppler Current Profiler (ADCP) can be used not only for measuring ocean currents, but also for quantifying suspended sediment concentrations (SSC) from acoustic backscatter strength based on sonar principle. Suspended sediment has long been recognized as the largest sources of sea contaminant and must be considered as one of the important parameters in water quality of seawater. This research was to determine SSC from measured acoustic backscattered intensity of static and mobile ADCP. In this study, vertically mounted 400 kHz and 750 kHz static ADCP were deployed in Lembeh Strait, North Sulawesi. A mobile ADCP 307.2 kHz was also mounted on the boat and moved to the predefined cross-section, accordingly. The linear regression analysis of echo intensity measured by ADCP and by direct measurement methods showed that ADCP is a reliable method to measure SSC with correlation coefficient ( ) 0.92. Higher SSC was observed in low water compared to that in high water and near port area compared to those in observed areas. All of this analysis showed that the combination of static and mobile ADCP methods produces reasonably good spatial and temporal data of SSC.

ANALISIS DAN KLASIFIKASI SEDIMEN PERMUKAAN DASAR LAUT MENGGUNAKAN SUB-BOTTOM PROFILER

Peningkatan aktivitas manusia di bidang kelautan seperti operasi pengerukan ( dredging ), eksplorasi minyak dan gas, penambangan pasir mineral, dan berbagai penelitian kelautan telah mengakibatkan permintaan yang mendesak terhadap peta dasar laut yang akurat. Sub-bottom Profiler (SBP) adalah sistem akustik tradisional yang digunakan untuk menggambarkan lapisan sedimen dan batuan di bawah dasar laut, serta memberikan informasi tentang ketebalan sedimen dan stratigrafinya. Oleh karena itu, tujuan dari penelitian ini yaitu menentukan profil lapisan sedimen dasar laut ( near-surface sediment ) dan memperoleh nilai koefisien refleksi dari lapisan tersebut. Proses akuisisi data dilakukan menggunakan SBP jenis sparker single channel oleh BPPT, yaitu survei pemeliharaan pipa migas dan kabel listrik Pertaminatahun 2010 yang berada di sebelah timur pantai Balongan, Indramayu. Pengambilan sampel sedimen dasar laut menggunakan gravity corer. Hasil dari pengolahan data mentah SBP dengan Matlab di dekat lokasi B19 diperoleh profil 2D dari lapisan sedimen dimana terlihat jelas dasar laut dan reflektornya serta memiliki nilai koefisien refleksi berkisar 0 hingga 0.2955. Selain itu teknik analitis untuk estimasi parameter sedimen dari data laboratorium ditunjukkan sebagai pembanding. Hasil sedimennya berupa silt/ lanau dengan nilai koefisien refleksinya adalah 0.2807.

Acoustical Measurement and Biot Model for Coral Reef Detection and Quantification

Coral reefs are coastal resources and very useful for marine ecosystems. Nowadays, the existence of coral reefs is seriously threatened due to the activities of blast fishing, coral mining, marine sedimentation, pollution, and global climate change. To determine the existence of coral reefs, it is necessary to study them comprehensively. One method to study a coral reef by using a propagation of sound waves is proposed. In this research, the measurement of reflection coefficient, transmission coefficient, acoustic backscattering, hardness, and roughness of coral reefs has been conducted using acoustic instruments and numerical modeling using Biot theory. The results showed that the quantification of the acoustic backscatter can classify the type of coral reef.

THE DETECTION OF PELAGIC FISH USING HYDROACOUSTIC IN PALU BAY, CENTRAL SULAWESI

Data potensi dan hasil tangkapan yang bersumber dari data statistik perikanan ataupun perikanan komersial sebagian besar belum lengkap dan akurat. Oleh sebab itu, upaya peningkatan akurasi data dan metode survey yang sesuai diperlukan untuk menjamin ketepatan sasaran pendugaan potensi sumberdaya ikan di Indonesia. Tujuan deteksi schooling ikan pelagis dengan hidroakustik ialah agar dapat memberikan gambaran akurat tentang kondisi insitu potensi sumberdaya ikan pelagis di Perairan Teluk Palu. Hasil penelitian menunjukkan bahwa schooling ikan pelagis dominan berada pada interval TS -70 dB s/d -40 dB sebanyak 23 schooling ikan. Berdasarkan strata kedalaman, schooling ikan lebih banyak berada pada kedalaman 100 s/d 150 m sebanyak 12 schooling disusul pada kedalaman 0 s/d 50 m sebanyak 9 schooling dan kedalaman 50 s/d 100 m sebanyak 2 schooling. Nilai TS tersebut merupakan kisaran nilai dari jenis pelagis besar. Hal tersebut sejalan dengan hasil tangkapan ikan di perairan Teluk Palu yang didaratkan di Pelabuhan Perikanan Labuan Bajo, Kabupaten Donggala yang didominasi jenis ikan pelagis besar. Ukuran terpanjang ikan cakalang senilai 74 cm di kedalaman 142 m. Ukuran terkecil senilai 5 cm di kedalaman 57 m dengan rata-rata ukuran 27.80 cm.Yield and catch data obtained from statistic and fisheries commercial data are incomplete and inaccurate. Effort to increase the accurate data and survey method become necessary to estimate the yield potential in Indonesia. The aim of this study is to detect the pelagic schooling (target strength/TS approach) by using hydroacoustic. Those detection are used to describe insitu condition of pelagic fishes in Palu Bay, Central Celebes. Result of this study showed that the range of TS interval of pelagic schooling are between -70dB to -40dB, found about 23 schools. Based on depth strata, dominant schooling (12 schools) found in 100 to 150 m, then followed by 9 schools in 0 to 50 m and 2 schools in 50 to 100 m. fish caught in Palu Bay that landed in Labuan Bajo fishing port dominate by large pelagic. Those information are relevant with the TS data. The longest size of skipjack is 74 cm in depth of 142 m. Medium size of the smallest value of 5 cm in depth 57 m with an average size of 27.8 cm.

Computation of Single Beam Echo Sounder Signal for Underwater Objects Detection and Quantification

Underwater Acoustic methods have been extensively used to locate and identify marine objects. These applications include locating underwater vehicles, finding shipwrecks, imaging sediments and imaging bubble fields. Ocean is fairly transparent to sound and opaque to all other sources of radiation. Acoustics technology is the most effective tool for monitoring this environment because of the sounds ability to propagate long distance in water. We used single beam echo sounder to discriminate underwater objects. Development of the algorithm and applied it to detect and quantify underwater object such as fish, sea grass, and seabed. We found the detected target has different backscatter value.

Underwater acoustic signal processing for detection and quantification of fish

Fish resources management have become increasingly important. In order to manage fish resources, the accurate estimates of fish characteristics such as target strength are needed. The present study describes development of an underwater acoustic instrument to detect, identify, and quantify of fish. The results also show that fish identification using signal processing of underwater acoustic signal is possible.

Designing acoustic transmitting receiving system for measurement of fish density

The underwater acoustic method is a powerful tool for assessment of fish abundance. The acoustic transmitting and receiving system was developed to measure fish target strength and fish density. From this study, we found the target strength of fish has a high correlation with fish length. By calculating the fish target strength with acoustic parameter we found the value of fish density.