Regional Seafloor Topography by Extended Kalman Filtering of Marine Gravity Data without Ship-Track Information

An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topographic heights composing an undersea volcanic mount by the successive combination of large numbers of gravity measurements at sea surface using altimetry satellite-derived grids and taking the error uncertainties into account. The integration of the non-linear Newtonian operators versus the radial and angular distances (and its first derivatives) enables the estimation process to accelerate and requires only few iterations, instead of summing Legendre polynomial series or using noise-degraded 2D-FFT decomposition. To show the effectiveness of the EKF approach, we apply it to the real case of the bathymetry around the Great Meteor seamount in the Atlantic Ocean by combining only geoid height/free-air anomaly datasets and using ship-track soundings as reference for validation. Topography of the Great Meteor seamounts structures are well-reconstructed, especially when regional compensation is considered. Best solution gives a RMS equal to 400 m with respect to the single beam depth observations and it is comparable to RMS obtained for ETOPO1 of about 365 m. Larger discrepancies are located in the seamount flanks due to missing high-resolution information for gradients. This approach can improve the knowledge of seafloor topography in regions where few echo-sounder measurements are available.

Pemodelan 3D Lapisan Dasar Laut Dan Identifikasi Ketebalan Sedimen Berdasarkan Kombinasi Data Pengukuran Sub-Bottom Profiler Dan Single Beam Echosounder (Studi Kasus: Alur Akses Timur Surabaya)

Pelabuhan merupakan salah satu fasilitas umum yang memiliki peran penting dalam keselamatan navigasi pelayaran. Shipping yang aman harus didukung dengan pemantauan dan pemeliharaan secara berkala untuk mendapatkan informasi terkini tentang kedalaman, dasar laut, dan sedimentasi. Jika sedimentasi terakumulasi secara terus menerus dalam waktu singkat di alur akses (jalur pelayaran), maka dapat meningkatkan kemungkinan terjadinya kecelakaan kapal. Kajian ini mencoba memetakan dan menganalisis kondisi batimetri dan sedimentasi untuk mendukung pemantauan dan pemeliharaan rutin alur akses Timur Pelabuhan Tanjung Perak Surabaya. Metode yang digunakan dalam penelitian ini adalah survei akustik berdasarkan data pengukuran Sub-Bottom Profiler (SBP) dan Single Beam Echosounder (SBES). Data yang diperoleh kemudian dikoreksi oleh Sound Velocity Profiler (SVP), data pasang surut, dan draft transduser. Kualitas data kemudian diuji berdasarkan IHO SP-44 2008 dan uji t-studentized dengan tingkat kepercayaan 95%. Hasil dari penelitian ini adalah model 3 dimensi, profil kedalaman, ketebalan, dan volume lapisan sedimen dasar laut. Hasil penelitian menunjukkan bahwa alur akses Timur Surabaya memiliki empat lapisan dasar laut yaitu permukaan dan tiga lapisan sedimen di bawahnya. Kedalaman lapisan bervariasi antara 3 m sampai 16,8 m. Kualitas data kedalaman lapisan atas dikontrol oleh IHO S-44 2008 dengan nilai uji hitung 0,509 (nilai toleransi ± 0,509), sedangkan kualitas data SBP (diukur menggunakan t-studentized uji) mendapatkan nilai hitung sebesar -1,287 dengan toleransi ± 1,96. Artinya kualitas datanya bagus. Berdasarkan model 3d, rata-rata ketebalan lapisan secara berurutan adalah 5,84 m, 1,072 m, 0,758 m, dan 6.355 m, sedangkan total volume sedimen adalah 24.894.422,949 m3.

Improvement of Accuracy and Precision of the LiDAR System Working in High Background Light Conditions

Background light noise is one of the major challenges in the design of Light Detection and Ranging (LiDAR) systems. In this paper, we build a single-beam LiDAR module to investigate the effect of light intensity on the accuracy/precision and success rate of measurements in environments with strong background noises. The proposed LiDAR system includes the laser signal emitter and receiver system, the signal processing embedded platform, and the computer for remote control. In this study, two well-known time-of-flight (ToF) estimation methods, which are peak detection and cross-correlation (CC), were applied and compared. In the meanwhile, we exploited the cross-correlation technique combined with the reduced parabolic interpolation (CCP) algorithm to improve the accuracy and precision of the LiDAR system, with the analog-to-digital converter (ADC) having a limited resolution of 125 mega samples per second (Msps). The results show that the CC and CCP methods achieved a higher success rate than the peak method, which is 12.3% in the case of applying emitted pulses 10 µs/frame and 8.6% with 20 µs/frame. In addition, the CCP method has the highest accuracy/precision in the three methods reaching 7.4 cm/10 cm and has a significant improvement over the ADC’s resolution of 1.2 m. This work shows our contribution in building a LiDAR system with low cost and high performance, accuracy, and precision.

Color ruler to confirm spectrophotometer results for nitro compound content in acidic wastewater from TNT processes

This study aimed to find an additional analytical reference procedure to verify the accuracy of single beam Spectrophotometer results that used to determine the concentration of nitro compound pollutants such as TNT, DNT, and MNT (Tri Nitro Toluene, Di Nitro toluene, and Mono Nitro Toluene respectively) in treated acidic wastewater generated from TNT manufacturing. This procedure was tested and confirmed to be a reference for a single-beam spectrophotometer. In this study 10 samples with known concentrations were taken and prepared for colorimetric analysis, the concentrations gradient from 10mg/L up to 60mg/L to make a ruler with gradient color, this ruler was suitable for high concentration samples but to specify the low concentration samples the procedure depended on adding a known concentration to the unknown concentration sample then this added concentration transferred the samples from unspecified color to specified color on the ruler consisted by known concentration mentioned above, the concentration of unknown concentration samples were specified by taking the concentration corresponding to the ruler color a subtracting the value of added concentration and the value of the remains was sample concentration. This study proved the reliability of this procedure to confirm single-beam spectrophotometer results, determining low concentration value of unknown concentration sample of TNT acidic wastewater, and then it can be used as a substituent of spectrophotometer in the event of malfunctions.

Estimation of Quercetin and Rutin Content in Hyouttunia cordata and Centella asiatica Plant Extracts Using UV-Spectrophotometer

Flavonoids are secondary plant metabolites normally found as pigmented compounds in plants. Quercetin and rutin are two important and commonly found flavonoids in nature and exhibit wide pharmacological effects such as antioxidant, anticarcinogenic, antiviral, anti-inflammatory, antidiabetic, and hepatoprotective activities as well as antimicrobial activity. In this study, quercetin and rutin content is being quantified in the plant extracts of Centella asiatica and Houttuynia cordata and considerable amounts of these two flavonoids were depicted. A single beam UV – Spectrophotometer was used to measure the absorbance of the standard as well as test solutions. Calibration curves were constructed for standard quercetin and rutin in such a way that x-axis denotes concentration and the y-axis denotes the absorbance. The calibration curves showed linearity at concentrations 5-25 ?g /ml of quercetin and rutin respectively with a good correlation coefficient (r) of 0.99 for both the curves. The absorbance of the two test extracts was obtained from the calibration curve and respective concentrations of quercetin and rutin for the two extracts were calculated. The amount of quercetin and rutin present was expressed as Total Flavonoid Content (TFC) i.e. the amount of the flavonoid in ?g present per mg of the respective plant extract. The quercetin content in both the plant extracts was found to be more (315.8 in Houttuynia cordata; 487.6 in Centella asiatica) than the content of rutin (152.2 in Houttuynia cordata; 171.0 in Centella asiatica).

Shock Hugoniot Data for Water up to 5 Mbar Obtained with Quartz Standard at High-Energy Laser Facilities

In this work, we present experimental results on the behavior of liquid water at megabar pressure. The experiment was performed using the HIPER (High-Intensity Plasma Experimental Research) laser facility, a uniaxial irradiation chamber of GEKKO XII (GXII) at the Institute of Laser Engineering (ILE), and the PHELIX at GSI (GSI Helmholtz Centre for Heavy Ion Research), a single-beam high-power laser facility, to launch a planar shock into solid multilayered water samples. Equation-of-state data of water H 2 O are obtained in the pressure range 0.50–4.6 Mbar by tuning the laser-drive parameters. The Hugoniot parameters (pressure, density, etc.) and the shock temperature were simultaneously determined by using VISAR and SOP as diagnostic tools and quartz as the standard material for impedance mismatch experiments. Finally, our experimental results are compared with hydrodynamic simulations tested with different equations of state, showing good compatibility with tabulated SESAME tables for water.

Measurement and Analysis of Acoustic Backscatter Value for Bottom Classification of waters Tidung Island

Sediment in a water has an important role for organisms, namely as a habitat, a place for foraging for food, and a place for spawning. These sediment can affect the composition of organisms in the water. The purpose of this study is to calculate the value of acoustic backscatter for the classification of the bottom of the water and to see the effect of sediment grain size on the backscatter value obtained from a single beam acoustic instrument. Data collection was carried out from 10 to 12 June 2021 in the water of Tidung Island, Seribu Islands, using the SIMRAD EK-15 single beam, single frequency 200 kHz instrument. Sediment sampling was carried out at 13 stations. The results showed that the waters of Tidung Island were dominated by muddy substrate which was classified based on the Surface Backscattering Strength (SS) value. Meanwhile, the grain size of the sediment affects the SVb value, where the large the grain size of the bottom sediment, the SVb value will be higher. The higher SVb value the SS value will be higher. Keywords: Bottom Classification, Acoustic Backscatter, Tidung Island