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Detailed information on lake bathymetry is essential for both hydrology-related studies and water resource management. Conventionally, lake bathymetry was mapped using high-cost approaches (e.g., ship/boat-based multibeam echosounders or airborne bathymetric lidars). With only satellite remotely sensed data sets, a method for deriving high-resolution bathymetry for dynamic areas was proposed by combining the new Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) lidar data and the Landsat-based Global Surface Water Data Set (GSWD). First, ICESat-2 can provide accurate along-track topographic points after the point cloud processing and bathymetric error correction, and the GSWD can supply water occurrence information within the lake dynamic area between 1984 and 2018. Second, using the derived relationship between the elevation and water occurrence, the bathymetric map of Lake Mead, USA, was produced with the dynamic area exceeding 235 km², elevation ranging nearly 37 m, and a resolution of 30 m. The local reference data (i.e., the airborne topographic lidar data and ship/boat-based bathymetric data) in six areas around Lake Mead were used for the validations. In general, the produced lake bathymetry achieved an accuracy of approximately 2 m in elevation with R² of 0.97. The proposed method is promising to obtain global bathymetry for inland water bodies (e.g., the lake and reservoir) and coastal areas (e.g., the tidal zone) where water level fluctuations are strong and the water clarity is sufficient.

During the campaign of 2018 the international underwater archaeological expedition has explored the waters of Tendra Spit and Kinburn Spit on the shelf of the Black Sea, in Mykolaiv and Kherson regions of Ukraine. Underwater archaeological exploration focused on the waters near the northern tip of Tendra Spit, from both the Gulf of Tendra and the sea, and north-western tip of Kinburn Spit. In addition to the visual reconnaissance, divers were using sonar, profiler and side-scan sonar. As a result, the bathymetric map has been compiled. In the initial part of research the work was limited to mapping and taking photographs of the discoveries. During these works was discovered and cleansed the ancient Shipwreck of the late 4th — early 3rd century BC. It was possible to identify the well-preserved fragment of the hull of ancient Wreck of a length of 9.45 m in situ with ballast stones, ceramic material from the cargo, lead plating and him constructions elements. After clearing of the sand from the preserved part of the ship hull with the help of a hydro injector the video and photo documentation was carried out. As a result of these works, large-scale photo mosaic of the object and its 3D-model were made. The condition of the wooden hull is excellent, the technological holes, connections, bronze and iron nails are preserved. Outside of Ukraine several shipwrecks of the same period are attested. The best studied are the following: shipwreck of the 3rd century BC at Grand Congloue, France; the Mazotos shipwreck of the 4th century BC in Cyprus; the Porticello shipwreck of the end of the 5th or beginning of the 4th century BC in Italy; the Alonnisos shipwreck from the end of the 5th century BC, Greece; the Kyrenia shipwreck from the end of the 4th — beginning of the 3rd centuries BC in Cyprus. In the Black Sea, in 2011 a shipwreck from the end of the 4th — beginning of the 3rd centuries BC near Eregli, Turkey (ancient Herakleia Pontica) was discovered by a deep-sea expedition of the research vessel «Nautilus» under the direction of Michael Brennan at a depth of 101 m. Most of the known merchant ships of this period were small, ranging from 12 to 17 m (table). Boris Peters provides a reconstruction sketch of the Lake Donuzlav ship of the late 4th — early 3rd centuries BC. It is almost identical to the reconstruction of the Kyrenia merchant ship, based on its hull which was preserved by 75 %, The replica named «Kyrenia 2» was built and made several voyages. It can be assumed that the Kinburn Spit ship found in 2018 was of similar appearance but further research will provide more detailed information.

Wetlands monitoring requires accurate topographic and bathymetric maps. Regular creation of these with minimal cost and reduced environmental impact, can be achieved using unmanned aerial vehicles (UAVs). This chapter introduces a set of systems needed to create this automation starting with an automatic image labeling system, an online classification system for differentiating land and water, offline bathymetric map creation, and online bathymetric map creation. All systems have been implemented, simulated, and field tested where possible.

The characterization of estuarine hydrodynamics primarily depends on knowledge of the bathymetry and topography. Here, we present the first comprehensive, high-resolution dataset of the topography and bathymetry of the Amazon River estuary, the world's largest estuary. Our product is based on an innovative approach combining spaceborne remote sensing data, an extensive and processed river depth dataset, and auxiliary data. Our goal with this mapping is to promote the database usage in studies that require this information, such as hydrodynamic modeling or geomorphological assessments. Our twofold approach considered 500 000 sounding points digitized from 19 nautical charts for bathymetry estimation, in conjunction with a state-of-the-art topographic dataset based on remote sensing, encompassing intertidal flats, riverbanks, and adjacent floodplains. Finally, our estimate can be accessed in a unified 30 m resolution regular grid referenced to the Earth Gravitational Model 2008 (EGM08), complemented both landward and seaward by land (Multi-Error-Removed Improved-Terrain digital elevation model, MERIT DEM) and ocean (General Bathymetric Chart of the Oceans version 2020, GEBCO_2020) topographic data. Extensive validation against independent and spatially distributed data, from an airborne lidar survey, from ICESat-2 altimetric satellite data, and from various in situ surveys, shows a typical vertical accuracy of 7.2 m (riverbed) and 1.2 m (non-vegetated intertidal floodplains). The dataset is available at https://doi.org/10.17632/3g6b5ynrdb.2 (Fassoni-Andrade et al., 2021).

The coastal area of the Madura Strait stretches from Surabaya City to the east to Situbondo Regency and includes the southern part of Madura Island. The aim of this research is to map the suitability of the waters and coastal areas of the Madura Strait using GIS modeling. Mapping of the designation of the waters and coastal areas of the Madura Strait was carried out by overlaying spatial data covering bio-physical parameters including water transparency, pH, water substrate, temperature, salinity, and depth. The designation of water areas is divided into three classes, namely capture fisheries, tourism and conservation purposes. The spatial data used comes from several sources, namely the results of water quality surveys, Landsat 8 satellite imagery, bathymetry data / sea depth and Rupa Bumi Indonesia (RBI) maps at a scale of 1: 25,000. For water quality data comes from the results of a survey by the Marine and Fisheries Service of East Java Province in 2019 at 78 observation points in the waters of the Madura Strait. Water quality parameters used in GIS modeling are pH, salinity, brightness and temperature. The data for each observation point were then interpolated using the Kringing method. Landsat 8 satellite imagery is used to map the condition of the bottom substrate waters. Meanwhile, the depth data was downloaded from GEBCO (General Bathymetric Charts of the Oceans). The result of overlaying thematic maps shows that 37.69% (8586.69 km2) of the area of the Madura Strait is suitable for capture fisheries activities, then 10.28% (2341.02 km2) is suitable for marine tourism areas and 19.06 % (4343.4 km2) suitable for conservation areas. Meanwhile, 32.97% (7511.94 km2) can be used as conservation and tourism areas.

International audience; This paper examines spatial variations in the geomorphology of the Ninety East Ridge (NER), located in the Indian Ocean. The NER is an extraordinary long linear bathymetric feature with topography reflecting complex geophysical setting and geologic evolution. The research is based on a compilation of high-resolution bathymetric, geological, and gravity datasets clipped for the study area extent (65° - 107°E, 35°S - 21°N): General Bathymetric Chart of the Oceans (GEBCO), Earth Gravitational Model (EGM2008, EGM96). The submarine geomorphology of the NER was modeled by digitized cross-sectional profiles using Generic Mapping Tools (GMT). The availability of the method is explained by 1) the free datasets; 2) the open source GMT toolset; 3) the available tutorials of the GMT and the codes explained in this work. Three segments of the NER were selected, digitized, and modeled: 1) northern 89°E, 7°S to 90°E, 7°N; 2) central 88.4°E, 14.7°S to 88.8°E, 8.2°S; 3) southern 87.9°E, 17°S to 87.5°E, 27°S. Measured depths were visualized in graphs, compared, and statistically analyzed by the histograms. The northern segment has a steepness of 21.3° at the western slopes, and 14.5° at the eastern slope. The slopes on the eastern flank have dominant SE orientation. The central segment has a bell-shaped form, with the highest steepness comparing to the northern and southern segments. The eastern flank has a steepness of 49.5°. A local depression at a distance of 50 km off from the axis (90°E) continues parallel to the NER, with the shape of the narrow minor trench. The western slope has a steepness of 57.6°, decreasing to 15.6°. The southern segment has a dome-like shape form. Compared to the northern and central segments, it has a less pronounced ridge crest, with a steepness of 24.9° on the west. The eastern flank has a steepness of 36.8° until 70 km, gradually becoming steeper at 44.23°. A local minor trench structure can be seen on its eastern flank (100 km off the axis). This corresponds to the very narrow long topographic depressions stretching parallel to this segment of the NER at 90.5°E. The study contributes to regional geographic studies of Indian Ocean geomorphology and cartographic presentation of GMT functionality for marine research and oceanographic studies.

Submarine topography is one of the key factors determining the course and direction of processes at the lithosphere–hydrosphere boundary. In this article, we present results of the first phase of a project to create a system for 3-D geomorphometric modeling of the Arctic Ocean floor. In this phase, a low-resolution desktop version of the system was developed. We utilized a small 5-km gridded digital elevation model extracted from the International Bathymetric Chart of the Arctic Ocean version 3.0. First, we smoothed the digital elevation model to suppress high-frequency noise. From the smoothed digital elevation model, we derived digital models of the following morphometric variables: horizontal, vertical, minimal, and maximal curvatures, catchment, and dispersive areas, as well as topographic and stream power indices. Then, to construct and visualize 3-D morphometric models of the territory, we applied an original approach for 3-D terrain modeling in the environment of Blender, free and open-source software. Finally, we present a series of the 3-D morphometric models (perspective views from the Atlantic, Eurasia, and North America). The experiment showed that the approach is efficient and can be applied for creating next desktop and web versions of the system for visualizing 3-D morphometric models of higher resolutions. The final versions of the system will be used to support marine geomorphological, geological, and biological studies of the Arctic Ocean.

Advance in the visualization of the bathymetric and geological data from charted to digital maps and models opened the possibility to analyse data within Geographic Information System (GIS) functionalities. In this paper, bathymetric and geological properties of the Adriatic Sea were analysed using the General Bathymetric Chart of the Ocean (GEBCO) 2020 digital bathymetric model (DBM) and data from the European Marine Observation and Data Network (EMODnet). The bathymetric analysis includes depth statistics, area and volume calculation, hypsometry, and analysis of the heterogeneity of bathymetric data from the GEBCO 2020 DBM within the limits of the Adriatic defined by the International Hydrographic Organization (IHO) and 3 sub-basins delineated according to the bathymetry. The geological analysis includes seabed substrate map from EMODnet data and kilometre-scale seabed variability in the Adriatic. The GEBCO 2020 DBM shows that the Adriatic Sea is a shallow sea with a mean depth of -253 metres and over 50% of area shallower than 100 metres. The area of the Adriatic Sea is 138 516 km2 with a total volume of 35 521 km3. Patterns describing morphological variability coincide with the heterogeneity of the underlying source data of the GEBCO 2020 digital bathymetry model and major structures in the Adriatic Sea., Napredak u načinu prikaza batimetrijskih i geoloških podataka s papirnatih karata u digitalne podatke i modele otvorio je mogućnost manipulacije i analize podataka u digitalnome okruženju geografskih informacijskih sustava (GIS). U ovome radu analizirana su batimetrijska i geološka svojstva Jadranskoga mora s pomoću podataka digitalnoga batimetrijskoga modela General Bathymetric Chart of the Ocean (GEBCO) 2020 i Europske mreže za nadgledanje i prikupljanje podataka o moru (EMODnet). Batimetrijska analiza uključuje statistiku dubina, izračun površine i volumena, hipsometrijsku krivulju i analizu heterogenosti batimetrijskih podataka unutar modela GEBCO 2020 na području Jadranskoga mora čije je granice definirala Međunarodna organizacija za hidrografiju (IHO) te triju dijelova Jadranskoga bazena podijeljenih s obzirom na dubinu. Analiza geoloških svojstava obuhvaća prostornu preraspodjelu sedimenata na temelju podataka EMODnet mreže i varijabilnost terena u kilometarskoj razlučivosti na području Jadrana. Prema podatcima digitalnoga batimetrijskog modela GEBCO 2020 Jadransko je more plitko more s prosječnom dubinom od 253 m i više od 50 % površine pliće od 100 m. Površina Jadranskoga mora iznosi 138 516 km2 , a volumen 35 521 km3. Crte kojima je definirana varijabilnost terena poklapaju se s heterogenošću podataka na temelju kojih je izračunan model GEBCO i većim geomorfološkim strukturama u Jadranu.

Empirical models have been widely used to retrieve shallow water bathymetry from multispectral/hyperspectral satellite imagery. In traditional studies on deriving the topography and monitoring its temporal changes, a single date satellite image without clouds corresponded to a bathymetric map and multidate images corresponded to multiple bathymetric maps. The satellite image noise caused by various environmental conditions and satellite sensors can inevitably introduce errors or gaps in deriving bathymetric maps. Also, empirical models are limited in some remote areas due to the lack of prior bathymetric points. In this article, using only satellite data, including multitemporal Sentinel-2 images and Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) data, a multitemporal stacking method was developed to derive highly accurate and cloud free shallow water bathymetry with accuracy of approximately 1 m and the depth range exceeding 22 m. The proposed method was tested and validated by an airborne bathymetric lidar. To be specific, our method using multitemporal Sentinel-2 images can achieve a mean root mean square error (RMSE) of 1.08 m (R2 = 0.94) by comparing with in-situ airborne lidar data around Ganquan Island, which is better than the result (R2 = 0.92, RMSE = 1.46 m) derived from single date image based methods.Also, the gaps in a bathymetric map due to clouds or other noise can be avoidable benefitting from the stacking of multiple date satellite images. In the future, this satellite data driven method can be further extended to the globe to produce highly accurate and cloud free bathymetry around clear shallow water benefited from prior ICESat-2 bathymetric data.

The modern technologies not only provide an opportunity to collect water depth data much more efficiently than in the past, but also there is a wide range of opportunities to process these data to develop bathymetric maps and perform various calculations in the computer environment. This research aims to construct a high-resolution bathymetric map by using open-source software. Lake Zebrus was selected as the study site, where fieldwork was performed to obtain the depth data and subsequently process to find optimal methodology for creating a bathymetric map. The methodology used in this research is modifiable for different purposes and is based on obtaining the best results from using open-source resources and knowledge of cartography. Lake Zebrus is an example how to perform accurate and state of the art bathymetric survey in a short time period. The area of Lake Zebrus is 417.57 ha. The lake has a small crooked coastline. Lake Zebrus has a maximum depth of 4.45 m and an average depth of 1.48 m. Results from the bathymetric survey can be used for further research based on depth data. The research tasks are accomplished as the methodology selected is repeatable in the other lakes. The research results prove that this methodology can be used for a bathymetric survey and it is possible to obtain high-definition results using open-source resources.

This study with a morphology and hydrosedimentology character was done to carry out a with an understanding the evolution of the channels and sedimentation in Potou lagoon in Ivory Coast starting from the realization of the bathymetric map. The bathymetry of this lagoon avered that the depths are lower than 2.11 m out of 22 km2, and presente three types of channels. In fact the channels in "U" represent a balance between the agents of accumulation and erosion. Channels resulting from processes of erosion which are in "V" and channels intermediate indicating an evolution of the type "V" in "U". In particular during these fourteen last years the Potou lagoon has sudden great phenomenon of deposit is a volume of +66791000.18 m³of sediments deposed on a surface which is thus estimated at 65.2 % of chenal surface. These deposits are certainly causes of full high funds in this lagoon. The mean velocity of sedimentation on Potou lagoon is thus estimated at 26.5 cm/year. As for the erosion, it could be estimated at-8487601 m³ a volume of on a surface wich is thus estimated at 34 % of chenal surface. The sedimentary budget would be thus estimated at+58303398.68449 m³ on a surface of 12.45 m2. A surface which is thus estimated at 0.8 %hasn’t sudden phenomenon of deposit or erosion. The bathymetric chart and the sedimentary budget of Potou lagoon are tools necessary for use of the stretch of water by the users. Thus, the zones at the risks determined on the bathymetric chart, such as the high bottom and the points of swirl generated by the depressions, will be easily avoided.

Based on a detailed bathymetric map of the southeastern part of the Magellan Seamounts created using the results of multibeam echo sounding, a lineament analysis of the seafloor relief was performed, linear landforms were distinguished and their azimuths were measured, and a rose diagram was constructed showing the lineament direction in the area. Models of the deep and subsurface deformation fields of the area that identify blocks with predominant extension and compression stresses were constructed. The block motions occur along the lines of sign changes of the stresses (block boundaries). The directions of the block boundaries are compared with the lineament direction and a conclusion is made on their spatial and genetic relationship. The systems of directions of the linear landforms and the boundaries of deep and shallow blocks are partially consistent with four main systems of the global regmatic network, which indicates a significant influence of the latter on the structural plan of the area. The stress redistribution is related to modern geological processes that lead to the formation of new features of the seafloor relief and partial destruction of the old guyot surfaces.

The maximum ocean depth so far reported is about 11 000 m, and is located in the Mariana Trench in the Western Pacific Ocean. The hybrid unmanned underwater vehicle, Haidou, is developed to perform scientific survey at the deepest parts of the Earth oceans. For vehicles working at the full-ocean depth, acoustic positioning is the most effective and popular method. The 11 000 m class acoustic positioning system is relatively massive and complex, and it requires specialized research vessels equipped with compatible acoustic instruments. As a compact testbed platform, it is impractical for Haidou to carry an LBL/USBL beacon with its large volume and weight. During the descent to about 11 000 m, horizontal drift could not be eliminated because of the hydrodynamics and uncertain ocean currents in the sea trials. The maximum depth recorded by Haidou is 10 905 m, and determining the precise location of the deepest point is challenging. With the bathymetric map produced by a multibeam sonar, the terrain contour matching (TERCOM) method is adopted for terrain matching localization. TERCOM is stable in providing an accurate position because of its insensitivity to the initial position errors. The final matching results show the best estimate of location in the reference terrain map.

The article presents the results of the efforts to create a digital elevation model of Kara-Bogaz-Gol Bay. The informational background for the digital elevation model was maps of 1:200 000 and 1:100 000 scales. The digital elevation model was created by digitizing topographic maps. The development process was organized sequentially in several stages. At the first stage, scanned images of topographic maps were referenced in accordance with the original coordinate system (Pulkovo 1942). Next, the maps were digitized. The resultant digital data were interpolated to the grid nodes. At the verification stage, the contour lines and depth values were visually checked on the basis of GRD models, and flaws were corrected. As a result, the digital elevation model of the bay bed was created with a spatial resolution of 100 × 100 m. Morphometric relationships were obtained for Kara-Bogaz-Gol – between the level and the area of the bay water surface, between the level and the storage of the bay. Kara-Bogaz-Gol Bay has an irregular shape. Its shores above -30 m BS elevation are steep and precipitous. Between -30 and -34 m BS elevation the shore slope is 30-45%, and an almost flat bed extends below -34 m BS. The rock basin morphometry of Kara-Bogaz-Gol Bay varies significantly depending on the water level in the sea and in the bay. The area of the waterbody remains almost invariable between -25 and -30 m BS height marks, and then shrinks towards -35.6 m BS elevation.

The algorithm for identifying geodynamic zones was based on an analysis of geological, geophysical, and tectonic maps of the Sea of Azov, a bathymetric map and oil and gas prospectivity data, structural maps for reflecting horizons in the Cretaceous, Maykop, Sarmatia, etc., geotechnical zoning maps, and power maps, taking into account the features spectral characteristics of the water surface in satellite images.The spatial distribution of the surface temperature of the Sea of Azov was obtained using the MODIS AQUA survey equipment for the last three years (months - April, May, September).In order to clarify the boundaries of geodynamic zones, intellectual integration of geospatial data was carried out, the result of which was the location scheme of geodynamic zones on the shelf of the Sea of Azov. The creation of a model for generating a useful signal on satellite images of the sea surface with the aim of assessing their environmental safety during oil and gas production is justified.Based on the results of processing all the available information, the following was established: the greatest environmental risks may arise during the exploitation of deposits in the southern geodynamic zone, it is safer, and in the environmental respect, oil and gas exploration is the geodynamic zone in the central part of the sea. The safest zones include the northern coastal shelf zone.

A bathymetric and sedimentological analysis carried out respectively in July 2017 and April 2018 made it possible to characterize the sediments and the morphology of Lake Nafoun. The sediments of the lake consist of vases, fine to very coarse sands with average particle sizes ranging from 475.67 and 2111 μm. There is a predominance of very coarse elements (43.50%). The standard deviation of the lake sand is between 1.21 and 1.86 and is poorly classified. The skewness fluctuates between ?0.06 and 0.41. The sediments were deposited at the bottom of the lake due to a progressive decline in the flow of water that carried them. Moreover, this study made it possible to realize the first bathymetric chart of Lake Nafoun, 42 years after its impoundment in 1975.

We have developed a web-based processing system that can simulate positive and negative sea level changes globally by selecting the best Digital Elevation Model (DEM) for a target region from multiple DEMs. A PNG elevation tile format is used as the DEM format, which reduces the DEM data size. The PNG tile format implements client-based processing, and the DEM data are provided from different websites. In addition, the smart tile architecture is adopted, which enables on-demand simulation by adding a tile conversion process (i.e., a DEM selection process) during image drawing by using JavaScript. To demonstrate the system, we have employed three DEMs, i.e., the Geospatial Information Authority of Japan (GSI) map (~10-m resolution), the ASTER Global Digital Elevation Models (ASTER GDEM version 3) as global land area (~30-m resolution), and the General Bathymetric Chart of the Oceans as bathymetric data (~1000-m resolution). The ASTER Global Water Bodies Database is also used in the data selection process. The GSI provides their DEM in a PNG elevation tile format, and the other data are provided by the Geological Survey of Japan in PNG elevation tile format. We assume the current DEM sea level as 0 m, and the sea level can be changed to an arbitrary integer value (−10,000 to 10,000 m). Combining ASTER GDEM for land and GEBCO for sea makes it possible to target DEM of the whole earth. Moreover, it was shown that if a higher resolution DEM is available, it is possible to combine the higher resolution DEM in that area. The combining the PNG elevation tile format with the smart tile architecture demonstrates the possibilities of a client-based web processing service like that of the server-based OGC Web Processing Service.

Identifying benthic substrates is important to researchers studying aquatic organisms in fresh and salt water systems. Benthic substrates are often not visible from the surface making it necessary to find another method to gather these data. Previous research has demonstrated that low cost side-scan sonar is a reliable way to identify hard substrates, such as rock and gravel, in a small, freshwater stream. In this study, the reliability of the side-scan sonar to accurately identify softer substrates such as grass and mud was tested in a large, brackish lagoon system. A total area of 11.55 km2 was surveyed with the sonar. Videos and pictures were taken at various points to groundtruth the sonar images and provide a measure of accuracy. Five substrate types were identified: dense seagrass, sparse seagrass, mangrove soil, mangrove soil with rock, and silt. Unidentifiable substrates were classified as unknown. A manually zoned benthic substrate map was created from the sonar recordings. Dense seagrass was most accurately identified. Sparse seagrass was the least accurately identified. A bathymetric map was also created from the sonar recordings.

The bottom topography of the studied area of the South China Sea is characterized by an uneven distribution of depths, their sharp variations and the presence of a large number of seamounts. As a result of the research conducted, bathymetric profiles, a bathymetric map and a scheme of Faye anomalies were compiled. Geomorphological zoning was conducted. Sections of bottom distinguished by morphology were identified: 1) weakly dissected slope, steep (angles up to 15) in the upper part and more gentle (57) to the bottom of the deep-water step, 2) slope eroded by fluvial processes, 3) stepped slope, 4) chains of mountains and flat-topped hills, 5) accumulative bottom of the deep-water plain. It was established that the gravitational field as a whole reflects the complex structure of the bottom, and the local forms of the underwater relief are expressed in Faye anomalies. For elevations, zones of positive anomalies of Faye are marked, and sections of canyon-like valleys were mapped by an intense negative anomaly of the gravitational field to -60 mGal. In the process of endogenous evolution of the region, the relief became more complex. The primary endogenous continental slope was almost everywhere transformed by exogenous processes. Within the shelf, the filling of the basin led to the unification of all its projections into a single raised base. A significant role in the formation of the modern relief was played by large-scale repeated sea regressions, as a result of which the formation of the sedimentary cover was interrupted by periods of its erosion with the formation of planation surfaces. The Late Pleistocene peak of the regression (1618 thousand years BP), which caused the complete drainage of the shelf areas of the region, caused the erosion of the shelf and the movement of coarse clastic material through submarine canyons and valleys.

Shallow-water bathymetry based on multispectral satellite imagery (MSI) is an important technology for depth measurement, but it is difficult to obtain a bathymetric map with high reliability and no missing data because of the ubiquitous image noise. Here, we propose a time-series-based bathymetry framework (TSBF). First, a pixel-level time series is constructed using remote sensing images collected at multiple points in time. Then, a new time-domain denoising method, the maximum outlier removal method, is used to create an optimal image from this time series. Finally, bathymetric inversion is performed using this optimal image to obtain a bathymetric map. Anda Reef and northeastern Jiuzhang Atoll, which have complex noise features, were selected as test cases to validate the proposed framework. Results show that the proposed TSBF can obtain bathymetric maps with high accuracy, reliability, and no missing data, outperforming the conventional bathymetry framework based on a single image.

As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the influence of reefs. In this study, a 3D model experiment was carried out on a system consisting of eight three-cylinder floating breakwater modules under the influence of reefs. A wave attenuation mesh cage was incorporated at the bottom of the model. The floating breakwater system was slack-moored in its equilibrium position, and each module was connected by elastic connectors. The reefs were modeled on a bathymetric map of existing reefs in the East China Sea. In this experiment, the wave transmission coefficients, motion responses, and mooring forces of the floating breakwater system were measured. The results showed that the three-cylinder floating breakwater in the beam waves (β = 90°) has excellent wave attenuating performance under the influence of reefs, especially for short-period waves. However, under the influence of the reef reflection wave and the shallow water effect, the motion responses in the three main stress directions of the floating breakwater were large, and there was some surge and pitch motion. Under the influence of the aggregation and superposition of reflected waves on both sides of the reefs, the peak mooring forces in the middle position of the floating breakwater system were the largest at large wave height. The three-cylinder floating breakwater exhibited satisfactory hydrodynamic performance under the influence of reefs. It has broad application prospects in offshore reefs.

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.

Detailed knowledge of shelf bathymetry is essential for understanding the long-term geological evolution of continental margins, the extent of the coastal plain as the shoreline moved in response to Pleistocene sea-level fluctuations, and for ecosystems management, resource exploration, and navigation. Although some areas have been mapped in detail, most South African shelf bathymetry is poorly resolved. This paper presents a bathymetric map of the South African continental shelf derived from digital single-beam echo-sounding data collected by the Department of Agriculture, Forestry and Fisheries (DAFF) that is at a significantly higher resolution than was previously available as presented by Dingle et al. (Annals of the South African Museum 98:1–27, 1987). The bathymetric dataset consists of approximately 7 million data sonar points collected by the Fisheries Division of DAFF over the last two decades, covering the entire South African continental shelf area of 541,000 km2 between the Orange River mouth on the West Coast and Kosi Bay on the East Coast. The new map not only resolves known shelf bathymetric features in greater detail but also reveals new features. The origin of some bathymetric features remains unknown, but many appear to relate to bedrock geology, sediment deposition (river drainage systems and ocean currents), and sea-level fluctuations.

Monitoring and assessing the distribution of economic areas in East Africa such as low and high income neighborhoods, has typically relied on the use of structured data and traditional survey approaches for collecting information such as questionnaires, interviews and field visits. These types of surveys are slow, costly and prone to human error. With the digital revolution, a lot of unstructured data is generated daily that is likely to contain useful proxy data for many economic variables. In this research we focus on satellite imagery data with applications in East Africa. Recently East African cities have been developing at a fast pace by building new infrastructure and constructing innovative economic zones. Moreover with increased urban population, cities have been expanding in multiple directions affecting the overall distribution of areas with economic activity. Automatic detection and classification of these areas could be used to inform a number of policies such as land usage and could also assist with policy enforcement monitoring. On the other hand, the distribution of different economic areas in a specific city could provide proxies for various economic development variables such as income distribution and poverty metrics. In this research, we apply deep learning techniques to satellite imagery to classify and assess the distribution of various economic areas of a specific region for urban planning. By benchmarking performance against various state-of-art models, results show that the proposed deep learning techniques yielded superior performance with an f1-score of 99%.

In this study, we present a new method called BathySent to retrieve shallow bathymetry from space that is based on the joint measurement of ocean wave celerity (c) and wavelength (λ). We developed the method to work with Sentinel 2 data, exploiting the time lag between two Sentinel 2 spectral bands, acquired quasi-simultaneously, from a single satellite dataset. Our method was based on the linear dispersion law, which related water depth to wave celerity and wavelength: when the water depth was less than about half the dominant wavelength, the wave celerity and wavelength decreased due to decreasing water depth (h) as the waves propagated towards the coast. Instead of using a best weighted (c,λ) fit with the linear dispersion relation to retrieve h, we proposed solving the linear dispersion relation for each (c,λ) pair to find multiple h-values within the same resolution cell. Then, we calculated the weighted averaged h-value for each resolution cell. To improve the precision of the final bathymetric map, we stacked the bathymetry values from N-different datasets acquired from the same study area on different dates. We first tested the algorithm on a set of images representing simulated ocean waves, then we applied it to a real set of Sentinel 2 data obtained of our study area, Gâvres peninsula (France, 47°,67 lat.; −3°35 lon.). A comparison with in situ bathymetry yielded good results from the synthetic images (r2 = 0.9) and promising results with the Sentinel 2 images (r2 = 0.7) in the 0–16 m depth zone.

Deploying long-range Autonomous Underwater Vehicles (AUVs) mid-water column in the deep ocean is one of the most challenging applications for these submersibles. Without ex ternal support and speed over the ground measurements, Dead-Reckoning (DR) navigation inevitably experiences an error proportional to the mission range and the speed of the water currents. In response to this problem, a computationally feasible and low-power Terrain Aided Navigation (TAN) system is developed. A Rao-Blackwellized Particle Filter (RBPF) robust to estimation divergence is designed to estimate the vehicle’s position and the speed of water currents. To evaluate performance, field data from multi-day AUV deployments in the Southern Ocean are used. These form a unique test case for assessing the TAN performance under extremely challenging conditions. Despite the use of a small number of low-power sensors and a Doppler Velocity Log (DVL) to enable TAN, the algorithm limits the localisation error to within a few hundreds of metres, as opposed to a DR error of 40 km, given a 50 m resolution bathymetric map. To evaluate further the effectiveness of the system under a varying map quality, grids of 100 m, 200 m and 400 m resolution are gen erated by sub-sampling the original 50 m resolution map. Despite the high complexity of the navigation problem, the filter exhibits robust and relatively accurate behaviour. Given the current aim of the oceanographic community to develop maps of similar resolution, the results of this work suggest that TAN can enable AUV operations of the order of months using global bathymetric models.

Para la cartografía y monitoreo de los arrecifes de coral, un mapa batimétrico es útil como un mapa base. Diferentes métodos han sido desarrollados para cartografiar la batimetría usando sensores remotos. Dos grandes grupos se pueden distinguir. El primero utiliza datos de teledetección de sensores activos y el segundo se basa en el empleo de sensores pasivos para generar información multiespectral. Este artículo se centra en el método de datos provenientes de sensores pasivos. Una modificación al método DOP “Profundidad de penetración” mediante espectrometría que se llevó a cabo en imágenes Landsat ETM+ sobre Archipiélago de San Andrés y Providen- cia (Colombia). Las mediciones de profundidad utilizadas en la validación del mo- delo fueron derivadas de lecturas de ecosonda en campo e interpolación de mapas batimétricos. La exactitud de la prueba reveló que el modelo batimétrico resultante es útil para el mapeo en zonas de arrecifes de coral del mar Caribe hasta 25m de profundidad aproximadamente. Los datos no conformes a la realidad fueron gene- rados por suposiciones inherentes a la teoría utilizada, la interpolación de datos, las características de la imagen de satélite y los errores durante la ejecución del método.

International audience; Because of its size and geographical position, the Cherbourg roadstead appears as a favourable site for Marine Renewable Energy (MRE) industry. As a result, Cherbourg harbour has undergone profound changes (2015 and 2016) due to the installation of industrial infrastructures to service the needs of expanding MRE further offshore. However, little is known about the morpho-sedimentary distribution and associated dynamics of seabed sediments before and after harbour transformations. This study focuses on sedimentary dynamics using detailed morphological and sedimentological analyses based on data acquired before changes (2012). The main map includes a unique bathymetric map (1:35,000) and sedimentary maps showing the percentage of the characteristic grain size fractions of 184 seabed samples. Despite the high tidal conditions, the roadstead construction had a significant impact on the sedimentary facies and distribution. This study provides a basis for future investigations on geomorphological evolution linked to the impact of anthropogenic development.

Hasanlar Dam and Hydroelectric Power Plant are located on Kucuk Melen Creek in the Western Black Sea Basin of Turkey. The dam was constructed in 1974 to provide domestic water needs of the Duzce Province, to supply irrigation water need, to control and mitigate floods and to produce hydroelectric power. This dam has been subjected to severe sedimentation since its construction in 1974. Therefore, bathymetric field survey studies were conducted to determine storage loss in the Hasanlar Dam reservoir by sedimentation. Bathymetric survey data from the reservoir site of the Hasanlar Dam were obtained in 1979, 1999 and 2014. Analysis of the bathymetric data, GIS and remotes sensing techniques showed that storage loss in reservoir active volume between 1974 and 1999 was 24% and between 1974 and 2014 storage loss was 26%. Analysis of the bathymetric maps also showed that sediment accumulation is severe near and around the dam body and the spillway whose discharge capacity was decreased by sediment accumulation. This is extremely critical because the flood of May 1998 caused the high risk of collapse of dam due to reduced capacity of the spillway. Remote sensing technique was used to determine the future deposition of sediment in the reservoir. For this purpose, 35 points in the reservoir area were determined by comparing the relative water depths and actual water depths using satellite image of the bathymetry in July 2017 and Lake Observation Station. High correlation (R2 = 0.833) was calculated by using logarithmic nonlinear regression analysis between actual and relative water depths for those 35 control points. The average of absolute values of differences between the estimated and actual water depths was found as 1.06 m, and RMSE was calculated as 1.25 m. This analysis shows that in the future, remote sensing data can be used in the studies of determining the depth of water and the total sediment thickness. In addition, the volume of the entire reservoir can be predicted by measuring the actual water depth only at those 35 control points without making a bathymetric map of the whole dam reservoir.

Access to reliable and accurate bathymetric data is fundamental to many marine activities. This paper proposes a merge-normalization (MN) method that is suitable for multisource bathymetric data fusion in deep ocean areas, to solve the problem of difficult to integrate high-precision digital bathymetric model (DBM) for complex sources and various resolutions of global deep ocean bathymetric data. Then we apply it to the DBM construction of the Mariana Trench. The method combines multibeam, single-beam, and electronic navigational chart data with Shuttle Radar Topography Mission (SRTM) dataset by using the workflow of merging and normalizing, which can fill the data gaps while preserving topographic details in high-resolution bathymetric data. Compared with the widely used General Bathymetric Chart of the Oceans (GEBCO) dataset, the Mariana Trench dataset constructed in this study demonstrated improved accuracy, resolution, and topographic detail, highlighting the value of the application of the method and of its development potential.

The author would like to thank James H Churchill, Larry Pratt, and Jim Thomas for the discussions and help. The topography data are derived from General Bathymetric Chart of the Oceans (GEBCO: https://www.gebco.net/). The initial salinity and temperature is extracted from World Ocean Atlas 2009 (WOA09: https://www.nodc.noaa.gov/OC5/WOA09/pr_woa09.html). The barotropic tidal boundary currents and the spatial distribution of elevation amplitudes and phases are derived from TPXO 7.2 inverse model (http://volkov.oce.orst.edu/tides/global.html). The MITgcm model output data files, sea level data from gauges, and mooring data can be found at Figshare (https://figshare.com/projects/Data_for_B2018JC013970_bc_redsea/57407). The research reported in this manuscript was supported by King Abdullah University of Science and Technology. This research made use of the resources from the Supercomputing Laboratory and/or computer clusters at King Abdullah University of Science and Technology.

The article describes the experience of using the GPR method to study the bottom sediments of Lake Upoloksha located in the Kola Peninsula, Russia. Such sediments are viewed as good archives of various Holocene geodynamic processes, including tectonic and paleoseismic events. This small lake is located in the zone of the active NW-striking lineament, which length is more than 20 km. A series of åsars (eskers) stretches along the lineament. In the previous studies, the bottom sediments of the lake were investigated by geological methods, including core sampling, lithological and micro-palaeontological analysis of sediments. The studies have revealed a horizon which features are indicative of catastrophic changes in the sedimentation conditions due to a single impact. Our study aimed at evaluating the level of informativeness of the GPR method for detecting disturbances in the bottom sediments and new paleoseismic dislocations. The study referred to the hypothesis of the distribution of seismic foci in the Kola Peninsula in the Holocene. A ground-penetrating radar OKO-2 and an antenna unit (150 MHz) were used to survey of Lake Upoloksha in detail. The positions of the main stratigraphic horizons of the bottom sediments were clarified, and their thicknesses were measured more precisely. The GPR measurement error in comparison to the drilling data did not exceed ±0.2 m, which corresponds to the resolution of the antenna used in the survey. The GPR data confirmed the existence of seismic dislocations identified by the geological methods and discovered new zones of displacement and deformation in the organogenic and mineral bottom sediments. The survey detected vertical displacements, which amplitudes vary from 1.3 to 1.7 m, and landslides caused by seismogravitational rock collapse. Based on the GPR data, a bathymetric map was constructed. It shows the positions of the two basins of Lake Upoloksha. The survey provided the basis for a model showing the isosurface of the top of the mineragenous sequence. In the central part of the mineral-base model, there is a series of individual stepwise blocks of the sublatitudinal strike, which result from seismic movements. The GPR survey of Lake Upoloksha demonstrates that the GPR method can be successfully applied to estimate the mineral and organogenic parts of the bottom sediments, study their lithostratigraphic features, and detect changes in the structure of the bottom sediments. Based on the GPR data, it becomes possible to map even the small-scale disturbances.

The topography data is derived from General Bathymetric Chart of the Oceans (GEBCO: https://www.gebco.net/). The open boundary conditions are extracted from the Estimating the Circulation and Climate of the Ocean (ECCO) product (https://ecco.jpl.nasa.gov/products/). The data supporting the analysis presented here can be found at Figshare (https://figshare.com/articles/Data for 2018JC014531R/7243184/). The research reported in this manuscript is supported by King Abdullah University of Science and Technology (KAUST) and made use of the resources of the Supercomputing Laboratory and computer clusters at KAUST.

At the beginning of limnology, Lake Chudsk was entirely included in the Russian Empire. The first research answered the need to better understand and preserve fishery resources. Karl von Baer initiated the project in the 1850s. In the same years, research was carried out on the entire lake and its outfall, the Narva, in order to channel its energy while lowering the lake water level and then take advantage of its energetic potential. In the 1860s, the geologist Gregor von Helmersen wrote the first complete monograph of Lake Chudsk, but it was not until the 1895 campaign led by the geographer Joseph Spindler that the first bathymetric map of the lake was produced and the isothermal pattern of the temperature at all depths were plotted. Before Estonia became independent at the end of the First World War, most of the limnologists working on Lakes Chudsk and Pskov were German-Baltic scientists of Russian citizenship, favoring the encounter of several scientific cultures.

Gaza’ coastal zone suffers from permanent erosion as a result of the anthropogenic intervention. This study aims to assess and map land-use / land cover and shoreline changes in Gaza coastal zone using remote sensing and GIS tools as a step towards implementing coastal zone management. In addition, bathymetric map will be extracted using Landsat-8 image. Firstly, land-use / land cover change detection was carried out using SPOT-5, Landsat and Quick Bird for the years 2004, 2009 and 2016. Six classes were assigned to the study area using maximum supervised classification to investigate the evolution during past period. Secondly, change detection along the shoreline was implemented over the past 42 years from 1972 to 2014. Finally, the ratio transform technique was applied to the newly acquired multi-spectral image to extract the nearshore bathymetric map of the coastal area. Results of change detection revealed that coastal area was significantly changed: urban/built-up and agricultural area expanded, whereas area of bare land / sand shrank by 14,52 km2. In addition, shoreline analysis showed that, northern regions were substantially eroded by 186,15,103 m2 in the period 1998–2007. Moreover, an accretion occurred at the southern beach of Gaza's fishing port with a rate of 9,53,103 m2/year during the period 2007–2014. Ultimately, it is concluded that ratio transform algorithm used to extract bathymetry could retrieve depths from -25 m to -30 m. In addition, the result shows a good correlation between the estimated algorithm depths and the observed depths.

On October 30th 2020 a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea. This seismic event was another destructive active deformation in the long seismic history of Samos since the ancient times. Preliminary reports focused the seismic epicenter at about 10 km north of Karlovassi, situated at the western part of the Samos E-W trending coastline. The earthquake mechanism corresponds to an E-W normal fault dipping to the north. The activated fault was assumed to be running along the northern margin of Samos Island, which bounds from the south the Samos basin.Immediately after the seismic activity and during the aftershock period in December 2020 an hydrographic survey off the northern coastal margin of Samos Island was conducted with R/V NAUTILOS of the Hellenic Navy Hydrographic Service, using the multibeam SeaBat 7160 RESON. The result of the hydrographic survey was a detailed bathymetric map with 15m grid interval and 50m isobaths. The main morphological aspects of Samos Basin are a 14 km long, 6 km wide and 690 m deep elongated E-W basin developed north of Samos Island.The southern margin of the basin is abrupt with morphological slopes of more than 10o, following the major E-W normal fault surface, running along the coastal zone, with an overall throw of more than 500m. In contrast, the northern margin of the basin shows a gradual slope increase towards the south from 1o to 5o. Numerous small canyons trending N-S transversal to the main direction of the Samos coastline are observed along the southern margin, between 600 and 100 m water depth. These canyons have a length around 2,7 km and width between 100-300 m. Two large submarine landslides with a canyon width of 1,3 km and 0,8 Km, are located north of Karlovasi. The creation of the canyons is probably due to the uplift of Northern Samos Island and their 500 m vertical height difference corresponds to the average fault throw that has controlled the steep slopes of the margin. The orientation of the fault scarp changes at the western Samos coastline from E-W to ENE-WSW facing the neighboring Ikaria Basin, which is developed to the west of Samos Basin. The division line between the Ikaria and Samos basins runs N-S from the northern slopes and coast of the Kerketeas mountain (1443m). The aftershocks of the 30th October main shock are limited east of the N-S division line with only a minor activity 15 km to the west within the eastern margin of the Ikaria Basin.

Until the year 2019 only around 15% of the Earth’s seafloor were mapped at fine spatial resolution (