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Experimental verification of turbidity tolerance of stereo-vision-based 3D pose estimation system
摘要： This paper presents the verification of the turbidity tolerance of a stereo-vision-based 3D pose estimation system for underwater docking applications. To the best of the authors’ knowledge, no studies have yet been conducted on 3D pose (position and orientation) estimation against turbidity for underwater vehicles. Therefore, the effect of turbidity on the 3D pose estimation performance of underwater vehicles and a method of operating under turbid conditions were studied in this work. A 3D pose estimation method using the real-time multi-step genetic algorithm (RM-GA) proposed by the authors in the previous works shows robust pose estimation performance against changing environmental conditions. This paper discusses how and why the RM-GA is well suited to effective 3D pose estimation, even when turbid conditions disturb visual servoing. The experimental results confirm the performance of the proposed 3D pose estimation system under different levels of turbidity. To demonstrate the practical usefulness of the RM-GA, docking experiments were conducted in a turbid pool and a real sea environment to verify the performance and tolerance of the proposed system under turbid conditions. The experimental results verify the robustness of the system against turbidity, presenting a possible solution to a major problem in the field of robotics.
关键词： Robustness against turbidity,Real-time multi-step genetic algorithm,Sea docking,3D pose estimation,Stereo-vision,Visual servoing
更新于2025-09-23 15:23:52
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Practical Performance and Prospect of Underwater Optical Wireless Communication
摘要： Underwater optical wireless communication has been merely a theory for a long time because light sources are too weak to use them as emitters for communications. In the past decade, however, underwater optical wireless communications have used laser diodes or light emitting diodes as emitters with visible light in high brightness with low power consumption. Recently, they have become practical. As described in this paper, recent trends of underwater optical wireless communication study, practical modems and prospective uses of underwater optical wireless communication are presented first. Next, optical characteristics of the seawater in various conditions are explained based on the experimental data measured using the profiler for underwater optics produced especially for this study. Then the prototype underwater optical wireless communication modem developed by our team is introduced. It was tested in several sea areas, which confirmed bi-directional communication in the 120 m range at 20 Mbps and a remote desktop connection between under water vehicles at 100 m range. In addition, one modem was set in air; other was set in water. The modems mutually communicated directly through the sea surface.
关键词： UOWC,turbidity,chlorophyll,LD,VLC
更新于2025-09-23 15:23:52
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Long-Term Agroecosystem Research in the Central Mississippi River Basin: Hyperspectral Remote Sensing of Reservoir Water Quality
摘要： In situ methods for estimating water quality parameters would facilitate efforts in spatial and temporal monitoring, and optical reflectance sensing has shown potential in this regard, particularly for chlorophyll, suspended sediment, and turbidity. The objective of this research was to develop and evaluate relationships between hyperspectral remote sensing and lake water quality parameters—chlorophyll, turbidity, and N and P species. Proximal hyperspectral water reflectance data were obtained on seven sampling dates for multiple arms of Mark Twain Lake, a large man-made reservoir in northeastern Missouri. Aerial hyperspectral data were also obtained on two dates. Water samples were collected and analyzed in the laboratory for chlorophyll, nutrients, and turbidity. Previously reported reflectance indices and full-spectrum (i.e., partial least squares regression) methods were used to develop relationships between spectral and water quality data. With the exception of dissolved NH3, all measured water quality parameters were strongly related (R2 ≥ 0.7) to proximal reflectance across all measurement dates. Aerial hyperspectral sensing was somewhat less accurate than proximal sensing for the two measurement dates where both were obtained. Although full-spectrum calibrations were more accurate for chlorophyll and turbidity than results from previously reported models, those previous models performed better for an independent test set. Because extrapolation of estimation models to dates other than those used to calibrate the model greatly increased estimation error for some parameters, collection of calibration samples at each sensing date would be required for the most accurate remote sensing estimates of water quality.
关键词： water quality,Mark Twain Lake,partial least squares regression,chlorophyll,hyperspectral remote sensing,nutrients,turbidity
更新于2025-09-23 15:21:01
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Plastic fiber evanescent sensor in measurement of turbidity
摘要： The construction and working principles of a plastic fiber sensor for examining the level of turbidity is studied in this paper. This work focuses on designing an inexpensive turbidity sensor that incorporates a pair of multimode fibers (MMF) that are attached side by side and their beveled tips are mounted vertically. The efficiency of different beveled angles is evaluated by simulation with Tracepro software. The reflected signal is collected by immersing the sensor head into a water mixture and analyzed for various concentration. It was found that there is a linear increment of output intensity when concentration of mixture is increased. The turbidity sensor is tested with real samples that are collected from lake, river and coastal areas to demonstrate its consistency with commercial apparatus in natural compounds. The results showed that the proposed sensor structure is able to produce reliable results in a dynamic range of detection from 0 to 1000 Nephelometric Turbidity Unit (NTU) to facilitate practical field measurements.
关键词： Optical fiber sensor,Tracepro software,Water quality monitoring,Turbidity
更新于2025-09-23 15:21:01
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A wide dynamic range and high resolution all-fiber-optic turbidity measurement system based on single photon detection technique
摘要： A high-resolution fiber-optic detection system has been developed to measure the wide dynamic range of turbidity. To obtain high-resolution measurement results, a high sensitive single photon detection technique (SPDT) has been used in the system. Based on fiber characteristics, a compact probe structure for fiber-optic integrated transceiver (FITP) is designed to transmitting and collection light signal, which has the capability of detecting turbidity in the narrow workspace. By combining the Beer-Lambert (B-L) law transmission law with single photon counting theory, a novel turbidity measurement theoretical model has been proposed, which shows a good exponential relationship over the whole measurement range from 0.01 to 1000 NTU (Nephelometric Turbidity Units). However, when detecting 0.01–0.1 NTU low turbidity, the experimental results turn into an approximate linear relationship, which good agrees with the proposed theoretical model. Last, some issues about the optimization of light intensity and requiring attention on constructing a practical distributed multi-point water turbidity remote monitoring system in the outdoors are also discussed. It was found that the system can achieve a measurement dynamic range as wide as 50 dB with a resolution better than 0.01 NTU in the range of 0.01–1000 NTU, which is suitable for some specific turbidity measurement in remote and narrow workspace.
关键词： Turbidity measurement,Single photon detection technique,Fiber-optic detection,Wide dynamic range
更新于2025-09-23 15:19:57
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[IEEE 2018 Eighth International Conference on Image Processing Theory, Tools and Applications (IPTA) - Xi'an, China (2018.11.7-2018.11.10)] 2018 Eighth International Conference on Image Processing Theory, Tools and Applications (IPTA) - A New Database for Evaluating Underwater Image Processing Methods
摘要： In this paper, we present a new, large-scale database on underwater image, which is called the NWPU underwater image database. This database contains 6240 underwater images of 40 objects. Each object is captured with 6 different levels of turbidity water, 4 lighting conditions and 6 different distances. Among them, we use the underwater images with turbidity value of 0 as Ground-truth. In addition, we captured the shadowless image of the object in the air and clear water. Different from other underwater databases, we capture underwater images with real high turbidity lake water instead of simulating the turbidity of water. This method ensures that the underwater images we captured are as close as possible to the real environment. We have given the database baseline which contains multi-scale Retinex with color restore (MSRCR) algorithms for enhancing images and four commonly used image quality evaluation criteria, including two full-references and two no-references methods. The four image quality evaluation methods include two no-reference and two full reference.
关键词： turbidity,underwater image,image quality evaluation,image enhancement and restoration
更新于2025-09-19 17:15:36
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[IEEE OCEANS 2018 MTS/IEEE Charleston - Charleston, SC, USA (2018.10.22-2018.10.25)] OCEANS 2018 MTS/IEEE Charleston - High-resolution structured light D sensor for autonomous underwater inspection
摘要： Sensors that can provide detailed 3D data underwater are a prerequisite for enabling autonomous inspection of e.g. seafloor integrity, ocean habitats and subsea installations with unmanned underwater vehicles. Sonars are currently the primary source of 3D data on moving platforms subsea but have limited depth and lateral resolution. Several optical approaches exist such as passive stereo, which have problems with textureless objects, and LIDARs which are slow and provide low lateral resolution. In this work we explore the use of structured light, to achieve high-resolution 3D of objects in an underwater environment. We have adapted a Gray Code Phase Stepping (GCPS) structured light approach to be more robust to the contrast degradation caused by the scattering and attenuation of light in water. The robustness towards increasing water turbidity has been verified in pool experiments. We achieve a depth resolution ranging from 1.4mm to 6.4mm depending on the turbidity when imaging an object at 1.1m distance with a pixel resolution of 1280x1024 at a framerate of 8Hz.
关键词： underwater,turbidity,Gray code,Structured light,3D
更新于2025-09-19 17:15:36
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Turbidity and RI Dependency of a Polymer Optical Fiber-Based Chromatic Sensor
摘要： An in-line and real time chromatic sensor for liquids based on plastic optical fiber was developed. It uses an air gap, fiber to fiber, transmission principle. Its dependency to turbidity and refractive index is studied and characterized. This information will provide the necessary knowledge for future implementation of more complex auto-compensations routines. Due to the predictable behavior of the sensor to variations of turbidity and refractive index, it is shown that a posterior compensation could be applied for the discrimination of color. The real-time color sensor can be used in different turbid liquids and contain different refractive indices.
关键词： colorimeter,optical fiber,chromatic sensor,refractive index,turbidity,in-line
更新于2025-09-12 10:27:22
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Development of a Cost-Effective Optical Sensor for Continuous Monitoring of Turbidity and Suspended Particulate Matter in Marine Environment
摘要： A cost-effective optical sensor for continuous in-situ monitoring of turbidity and suspended particulate matter concentration (SPM), with a production cost in raw materials less than 20 €, is presented for marine or fluvial applications. The sensor uses an infrared LED and three photodetectors with three different positions related to the light source—135o, 90o and 0o—resulting in three different types of light detection: backscattering, nephelometry and transmitted light, respectively. This design allows monitoring in any type of environment, offering a wide dynamic range and accuracy for low and high turbidity or SPM values. An ultraviolet emitter–receiver pair is also used to differentiate organic and inorganic matter through the differences in absorption at different wavelengths. The optical transducers are built in a watertight structure with a radial configuration where a printed circuit board with the electronic signal coupling is assembled. An in-lab calibration of the sensor was made to establish a relation between suspended particulate matter (SPM) or the turbidity (NTU) to the photodetectors’ electrical output value in Volts. Two different sizes of seashore sand were used (180 μm and 350 μm) to evaluate the particle size susceptibility. The sensor was tested in a fluvial environment to evaluate SPM change during sediment transport caused by rain, and a real test of 22 days continuous in-situ monitoring was realized to evaluate its performance in a tidal area. The monitoring results were analysed, showing the SPM change during tidal cycles as well as the influence of the external light and biofouling problems.
关键词： in-situ measurement,turbidity optical sensor,oceanography,suspended particulate matter
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Retrieval of Suspended Solids from Landsat-8 and Sentinel-2: A Tool for Coastal Monitoring in Extremely Turbid Waters
摘要： This study is focused on presenting a methodology for estimating Total Suspended Solids (TSS) over two key strategic sites in SW Iberian Peninsula. The dataset used includes multi-temporal Landsat-8 and Sentinel-2A imagery during 2016. The application of the effective ACOLITE processor and the high quality of SWIR bands improve the atmospheric correction in these extremely turbid waters. A multi-conditional algorithm that uses both red and NIR reflectance is able to provide accurate TSS retrievals in the upper and lower reaches of the Guadalquivir estuary and Cadiz Bay. The level of spatial detail afforded by these observations at fine resolution (10-30m) allows a much in deep understanding of the timing and importance of turbidity plumes. The results indicate that the proposed approach is effective for fusing both missions (MAE of 5.21 mg/L and 3.89 mg/L in estuary and bay, respectively), producing more frequency for continuous monitoring, which is particularly valuable at these latitudes that are severely covered (~50%) by clouds and sunglint. These findings encourage further research with great implications to establish a continuous framework for the upcoming high-resolution services relying on both missions.
关键词： Turbidity Plumes,Landsat-8,Total Suspended Solids,Sentinel-2,Cadiz
更新于2025-09-10 09:29:36