Accurate Refraction Correction—Assisted Bathymetric Inversion Using ICESat-2 and Multispectral Data

Shallow-water depth information is essential for ship navigation and fishery farming. However, the accurate acquisition of shallow-water depth has been a challenge for marine mapping. Combining Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) bathymetry data with multispectral data, satellite-derived bathymetry is a promising solution through which to obtain bathymetric information quickly and accurately. This study proposes a photon refraction correction method considering sea-surface undulations to address errors in the underwater photons obtained by the ICESat-2. First, the instantaneous sea surface and beam emission angle are integrated to determine the sea-surface incidence angle. Next, the distance of photon propagation in water is determined using sea-surface undulation and Snell’s law. Finally, position correction is performed through geometric relationships. The corrected photons were combined with the multispectral data for bathymetric inversion, and a bathymetric map of the Yongle Atoll area was obtained. A bathymetric chart was created using the corrected photons and the multispectral data in the Yongle Atoll. Comparing the results of different refraction correction methods with the data measured shows that the refraction correction method proposed in this paper can effectively correct bathymetry errors: the root mean square error is 1.48 m and the R2 is 0.86.

Assessing Marginal Shallow-Water Bathymetric Information Content of Lidar Sounding Attribute Data and Derived Seafloor Geomorphometry

Shallow-water depth estimates from airborne lidar data might be improved by using sounding attribute data (SAD) and ocean geomorphometry derived from lidar soundings. Moreover, an accurate derivation of geomorphometry would be beneficial to other applications. The SAD examined here included routinely collected variables such as sounding intensity and fore/aft scan direction. Ocean-floor geomorphometry was described by slope, orientation, and pulse orthogonality that were derived from the depth estimates of bathymetry soundings using spatial extrapolation and interpolation. Four data case studies (CSs) located near Key West, Florida (United States) were the testbed for this study. To identify bathymetry soundings in lidar point clouds, extreme gradient boosting (XGB) models were fitted for all seven possible combinations of three variable suites—SAD, derived geomorphometry, and sounding depth. R2 values for the best models were between 0.6 and 0.99, and global accuracy values were between 85% and 95%. Lidar depth alone had the strongest relationship to bathymetry for all but the shallowest CS, but the SAD provided demonstrable model improvements for all CSs. The derived geomorphometry variables contained little bathymetric information. Whereas the SAD showed promise for improving the extraction of bathymetry from lidar point clouds, the derived geomorphometry variables do not appear to describe geomorphometry well.

Ground water toxicity due to fluoride contamination in Southwestern Lahore, Punjab, Pakistan

The prevalence of dental/bone deformities provides motivation for studying the distribution, severity and sources of the Fluoride (F−1). The ground water samples (n = 77) were collected, from the districts of Lahore and Kasur of approximately 750 Km2 area. The water was analyzed for fluoride (F−), pH, electric conductivity (EC), alkalinity and hardness. The results revealed F− concentration ranges from 0.25–21.3 mg. An inverse relation between depth and fluoride concentration was observed. On the basis of cluster analysis three zones were identified. Highly toxic zone was a strip of 15 km wide and 3 km long, along Multan road from Sunder to Phool Nagar bypass, with fluoride concentration (08–21.3 mg/l). The highly toxic zone inhabited a number of industrial units, disposing off their waste water through soaking pits. These units contribute pollution to the shallow water, which further penetrates to the surroundings. Hence the shallow water (depth of 45–50 feet) was the most contaminated. The intensity of toxic effects decreases from highly to mild toxic zone. It was concluded that the problem was actually associated with the industrial waste water. Therefore, to overcome the issue, measures of supplying fresh drinking water from the deep aquifer as well as treatment of industrial water is suggested. HIGHLIGHT Industry was actually responsible for fluoride toxicity in the region rather than natural sources.

The Effect of Sunglint Correction for Estimating Water Depth Using Rationing, Thresholding, and Mean Value Algorithms

Satellite-Derived Bathymetry (SDB) is an alternative for obtaining shallow water depth data. The existence of images with various resolutions, the availability of a complete image band can develop the extraction results. This method is based on the principle of the satellite's visible band to estimate water depth. The mapping of shallow water depth is dependent on water conditions, both its brightness and surface. When the sensor senses a water object, the reflected reflection comes from the surface, and some sensors cannot penetrate the water object. The sun's position and the sensor's point of view when sensing it results in interference from the water surface (Sunglint). The sunglint effect on the image can be reduced by performing RGB band correction with NIR Infrared. This study aims to demonstrate the effect of Sunglint's correction on three SDB approaches, namely Thresholding, Rationing, and Mean Value on Worldview 3 imagery in Karimunjawa Islands, Central Java. This study's results indicate that the Sunglint correction on Worldview 3 imagery affects the depth extraction results. The best results are shown by Sunglint's correction using the Thresholding approach (B2-B7), which produces the best correlation with R2 of 0.7364 and (B7-B2) with R2 = 0.7351. Contrastingly, the lowest correlation was generated using the Mean Value ((B2 + B7) / 2) approach without Sunglint's correction with R2 = 0.4015. So this research proves that the Worldview 3 image with Sunglint correction can provide bathymetry data, especially in shallow waters.

Middle-to late Holocene environmental changes based on a multi-proxy lagoonal record, Klisova lagoon, Greece

<p>Coastal wetlands are dynamic environments prone to climatic and anthropogenic forcing and ideal settings to study past climatic and environmental changes.  In the eastern Mediterranean region and particularly in Greece, the climate presents high spatiotemporal diversity, while human activity is a significant factor in shaping the landscape. This study presents a sediment record from Klisova lagoon, situated in central Greece, at the eastern part of Messolonghi lagoon complex. The area is recorded from antiquity to have great anthropogenic activity. The paleoenvironmental synthesis was based on standard sedimentological analysis (grain size, TOC, magnetic susceptibility), joint micropaleontological and palynological analysis, X-ray Fluorescence scanning, and radiocarbon dating. The Bayesian age-depth model is based on radiocarbon dating and yields an age of 4700 cal BP for the base of the recovered sediment sequence. For the last 4700 years, the freshwater influx, the progradation of the Evinos river delta and related geomorphological changes control the environmental conditions (e.g. depth and salinity) in the lagoon system. Prior to 4000 cal BP, a relatively shallow water depth, significant terrestrial/freshwater input and increased weathering in the lagoon area are inferred. Elemental proxies and increased dinoflagellate and foraminifera abundances, which indicate marine conditions with prominent freshwater influxes, point to the gradual deepening of the lagoon recorded at the drilling site up to 2000 cal BP. The marine and freshwater conditions equilibrium sets at 1300 cal BP, and the lagoonal system seems to reach its present state. Maxima of anthropogenic pollen indicators during the Mycenaean (~3200 cal BP), Hellenistic (~ 2200 cal BP) and Late Byzantine (~ 800 cal BP) periods suggest intervals of increased anthropogenic activities in the study area.  </p>

Current trends in the development of dry cargo carriers for coastal, mixed and inland navigation

Object and purpose of research. This paper discusses characteristics and technical condition of dry cargo ships of limited sea, mixed and inland navigation in order to describe a methodology that allows predicting the composition of the fleet in the medium term. Materials and methods. This study relied on the database of Marine Engineering Bureau (MEB), register books of classification societies, as well as on initial drawings for baseline designs of ships under consideration. The work followed common methods of ship theory and ship design, as well as of naval structural mechanics, analysis and statistics. Main results. A prediction is given for fleet composition and structure until the year 2030, including the ships built after the year 2000, including the newbuilding orders for years 2020–2022. Conclusion. Today, there are about 1,052 dry cargo vessels in operation, 79 % of which are "old", and 21 % were built after the year 2000. Dry-cargo vessels of Volgodonmax class are still the most popular. Due to shallow water depth, these ships cannot be made bigger, so the only way to increase their cargo capacity is to increase their block coefficient and reduce lightship displacement. The first challenge is fully solved by "super-ample" lines currently adopted by MEB for mixed-navigation vessels like RSD59, RSD62, RSD79. As for the reduction of lightship displacement, i.e. steel weight, all the attempts to improve MEB solutions on ships of other designs have so far led to the opposite result, i.e. greater metal consumption and accordingly lower cargo capacity. Thus, it has been practically established that the only way to reduce lightship weight is to apply lighter materials.

Analysis of Morphological Characteristics of Collapsed Reservoirs in Korea

The purpose of this study is to analyze the basic specifications or items of 17,313 reservoirs distributed throughout Korea and in particular, to establish the relationships among the morphological characteristics of the reservoirs. In addition, the morphology index, the storage (S)–area of full water (A)–levee height (H) (S–A–H) relationship, and the storage(S)–area of full water (A) (S–A) relationship were determined for collapsed reservoirs. In this study, histograms for 11 parameters, such as storage capacity, area of full water, levee height, and basin area, were plotted, and the distributions of the reservoir parameters were examined. The morphology index was used to classify the reservoirs based on the depth, and the coefficient values of the relationships of S–A–H and S–A were used to compare S with both A and H or only A. The coefficient value of S–A–H was inversely proportional to S, and when the coefficient value was high, the storage was small. The coefficient value of S–A was proportional to S, and when the coefficient value was small, the storage wassmall. Cluster analysis was performed based on the given items to determine the characteristics of all the reservoirs and only the collapsed reservoirs. From the cluster analysis results, the reservoirs were divided into five groups: A, B, C, D, and E. There were 7,714 (14) in Group A, 6,053 (4) in B, 2,633 (2) in C, 745 (1) in D, and 168 (0) in E for all the reservoirs and collapsed reservoirs (with the values of the collapsed reservoirs in parenthesis). The morphological indexes werelow in the order of A > B > C > D > E, and the coefficient values of S–A–H were high in the order of A > B > C > E > D. The coefficient values of S–A were low in the order of A > B > D > C > E. Based on the clustered analysis results for 21 collapsed reservoirs, the reservoirs were clustered in the order of A (14) > B (4) > C (2) > D (1) > E (0). A reservoir with shallow water depth and small storage capacity has an inherent probability of collapsing. Therefore, the results of this study are useful for reservoir management and operation, as well as for the prevention of reservoir collapse.