Bathymetric Chart Research Articles

Morphometry of Gelionys and Žaliasis Lakes

Bathymetric surveys of Gelionys and Žaliasis Lakes (located in the Baltic Uplands, Aukštadvaris Regional Park, Lithuania) were carried out on April 21, 2020, from a boat with attached Lowrance HDI SKIMMER XDCR transducer (200 kHz), Simrad GO5 chartplotter and Lowrance Point-1 GPS/Glonass receiver. At the same time, the shorelines of the lakes were revised. Average distance between profiles was ~10 m and depth measurement accuracy up to 2–5 cm. Accuracy of water surface elevation measurement using GNSS receiver Topcon Hiper SR up to 1–2 cm. Later, detailed (0.5 × 0.5 m) digital lake bottom models (DEM) were developed, bathymetric plans of the lakes were created, the main morphometric features were calculated, the boundaries and area of the lake catchments were defined, and the physical-geographical characteristics of the lakes were described based on field observations and various data. Gelionys and Žaliasis are small lakes of glaciokarst origin. Gelionys Lake is oval-shaped while shape of Žaliasis Lake is closer to the circle. Despite small surface area the lakes are quite deep. According to survey data, the surface area of Gelionys Lake is 4.79 ha, water surface elevation 216.1 m a.s.l., maximum depth 19.8 m, mean depth 6.0 m, volume 288.3 thousands m3, catchment area 71 ha. The surface area of Žaliasis Lake is 2.14 ha, water surface elevation 120.9 m a.s.l., maximum depth 15.84 m, mean depth 5.7 m, volume 122.2 thousands m3, catchment area 60 ha. During the observation period (from May of 2018 to September of 2020), the annual amplitude of water level fluctuations in Gelionys Lake reached up to 0.47 m, and in Žaliasis Lake up to 0.33 m. Keywords: Gelionys, Žaliasis, glaciokarst, lake, bathymetric chart, morphometry, Lithuania, Aukštadvaris Regional Park.

Comment on “Sediment budget and morphological change in the Red River Delta under increasing human interferences” by N.D. Ve, D. Fan, B.V. Vuong and T.D. Lan [Marine Geology 431 (2021), 106379

In a recent paper, Ve et al. (2021) present sediment budget and morphological change in the Red River Delta under increasing human interferences. However, there are some fundamental flaws associated with applying kriging interpolation technique, sequential bathymetric charts and assessing elevation change between subsequent bathymetric surveys. In addition, their approach to calculating sediment budget is also inaccuracy caused by unreliable inferences. Consequently, their results contradict our current understanding of the Red River sediment dispersal system.

Pemodelan Sistem Informasi Geografis untuk Pemetaan Kesesuaian Wilayah Perairan dan Pesisir Selat Madura

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.

Bathymetric and Seismic Data, Heat Flow Data, and Age Constraints of Le Gouic Seamount, Northeastern Atlantic

Until the year 2019 only around 15% of the Earth’s seafloor were mapped at fine spatial resolution (<800 m) by multibeam echosounder systems (Wolfl et al., 2019). Most of our knowledge of global bathymetry is based on depths predicted by gravity observations from satellite altimeters. These predicted depths are combined with shipboard soundings to produce global bathymetric grids. The first topographic map of the world’s oceans so produced (Smith and Sandwell, 1997) had a resolution between 1 and 12 km, and subsequent improvements in data and filtering techniques led to several updates. The latest bathymetric grid of the General Bathymetric Chart of the Oceans (GEBCO_2020) uses the SRTM15+V2.0 data set, which has a grid spacing of 15 arc sec, equivalent to about 500 × 500 m at the equator (Tozer et al., 2019). This resolution does not imply that reliable depth data are available for each grid cell. There are vast areas of the oceans where the accuracy of these grids is limited by lacking shipborne multibeam data, which are needed for calibrating and ground-truthing predicted depths (Smith and Sandwell, 1994). The resolution and accuracy of the bathymetric grids are critical factors for global estimates of the number and size distribution of seamounts, in particular for small edifices of <1,000 m height (Wessel, 2001; Hillier and Watts, 2007; Kim and Wessel, 2011). A case in point is Le Gouic Seamount, located in the NE Atlantic about 100 km SW of Tropic Seamount on ca. 152 Ma crust, close to magnetic isochrone M24 (Bird et al., 2007). The seamount belongs to the Canary Island Seamount Province (CISP; van den Bogaard, 2013), also termed Western Saharan Seamount Province (WSSP) by some workers (e.g., Josso et al., 2019). It is listed in the Kim and Wessel (2011) seamount census with the ID KW-00902, located at 21.26216 ◦ W/23.0199 ◦ N, with a height of 498 m; hence it appears as a tiny cone in pre-2019 bathymetric grids (Figure 1a). After first mapping of large parts of the seamount by the French oceanographic survey vessel “Beautemps-Beaupre” in 2013, it is represented at its full height in the actual GEBCO_2020 grid, which is based on the SRTM15+V2.0 data set (Tozer et al., 2019). In this data report we present new multibeam bathymetric data for Le Gouic Seamount, mapping its full extent for the first time. The data were obtained during a transit of R/V METEOR cruise M146 in 2018. We also present a reflection seismic profile across the seamount that was shot during the mapping, and seafloor heatflow data obtained on a profile near the northeastern seamount base and co-located on the reflection profile. On the basis of this data we can place constraints on the age of the seamount, and speculate about possible rejuvenated magmatic activity.

Exploring structured scripting cartographic technique of GMT for ocean seafloor modeling: A case of the East Indian Ocean

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.

BATHYMETRIC AND GEOLOGICAL PROPERTIES OF THE ADRIATIC SEA

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.

MORPHOLOGICAL EVOLUTION OF THE BOTTOM OF THE POTOU LAGOON OVER THE LAST TEN YEARS (COASTAL ZONE OF COTE D'IVOIRE)

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.

The Use of USV to Develop Navigational and Bathymetric Charts of Yacht Ports on the Example of National Sailing Centre in Gdańsk

Apart from extensive infrastructure protection, modern yacht ports should primarily provide vessels with navigational safety associated with their maneuvering on the approach fairway, as well as mooring in the port aquatory. For this reason, yachts entering the harbor should have up-to-date, accurate, and reliable charts of the port and its surroundings. This article presents hydrographic surveys conducted in the National Sailing Centre (NSC) yacht port at the Gdańsk University of Physical Education and Sport (GUPES), whose aim was to define and develop unique bathymetric and navigational charts of the harbor and the approach fairway. These can be used for example to manage berths in the marina or inform about the depths in the yacht port and on the approach fairway. The chart of the NSC-GUPES and its approach fairway is Poland’s first cartographic image of a harbor, performed entirely on the basis of surveys conducted by an Unmanned Surface Vehicle (USV). The study results demonstrated that the use of a small-sized USV in bathymetric measurements of yacht ports and marinas was significantly more effective than the traditional (manned) hydrographic surveys. Such vessels allow measurements to be carried out in hard-to-reach locations, even between mooring vessels, and in the immediate vicinity of quays. Thanks to the implemented automatic mode of steering on sounding profiles, USVs are equally efficient and capable of carrying out hydrographic surveys on a larger waterbody, i.e., the approach fairway.

Škilietų ir Tabaliukų ežerų morfometrija / Morphometry of Škilietai and Tabaliukai Lakes

Depth measurements of Škilietai and Tabaliukai Lakes (located in the Baltic Uplands, Aukštadvaris regional park, Lithuania) were taken in January and February of 2019. At the same time, the shorelines of the lakes were revised. Measurements were made from ice; measurement density varies from 34 to 46 spots per hectare. Depth measurement accuracy up to 0,05 m in Tabaliukai Lakes and Lake Škilietai I, up to 0,1 m in Lake Škilietai II. Accuracy of spot coordinates and water surface elevation measurement using GNSS receiver Topcon Hiper SR up to 1–2 cm. Later, detailed (0.50 x 5 m) digital lake bottom models (DEM) were developed, bathymetric plans of the lakes were created, the main morphometric features were calculated, the boundaries and area of the lake catchments were defined, and the physical-geographical characteristics of the lakes were described based on field observations and various data. Škilietai and Tabaliukai are small and closed groups of lakes (each group consists of 2 lakes) of glaciokarst origin. Despite small surface area (1.7–5.3 ha) the lakes are quite deep (9.8–18.5 m). Differences in the surface area and volume (77.8–436.3 thousand m3) of lakes are due to large differences in catchment areas. The shape of the lakes is remarkably regular, close to the circle. Tabaliukai Lakes usually are connected through bog lag and share the same water level, meanwhile, the water level in Škilietai Lakes differs on average by ~0.20 m. During the observation period (from spring of 2018 to May of 2020), the amplitude of water level fluctuations in Škilietai Lakes reached 0,41–0,48 m, and in Tabaliukai Lakes 0,67 m. The differences in the area and volume of the studied lakes are mainly due to the very different area of the lake catchments. Keywords: Škilietai, Tabaliukai, glaciokarst, lakes, bathymetric chart, morphometry, Lithuania, Aukštadvaris Regional Park.

Tapelių ežero morfometrija ir baseino fizinės geografinės ypatybės / Morphometry of Lake Tapeliai and Physicalgeographical Characteristics of its Catchment

Depth measurements of Lake Tapeliai (located in Vilnius, Lithuania) were taken in February 2019. At the same time, the shoreline of the lake was revised. Measurements were made from ice in 767 spots. Depth measurement accuracy up to 0,05 m, accuracy of spot coordinates and water surface elevation measurement using GNSS device Topcon Hiper SR up to 1–2 cm. Later, a detailed (1 x 1 m) digital lake bottom model (DEM) was developed, a bathymetric plan of the lake was created, the main morphometric features were calculated, the boundaries and area of the lake catchment were adjusted, and the physi cal-geographical characteristics of the lake and its catchment were examined based on various data. Morphometric features of Lake Tapeliai measured and calculated in 2019 are as follows: coordinates of mean center 54.774378, 25.4468 (WGS), water surface elevation 136.48 m (in Height System LAS07 of Lithuania), surface area 13.14 ha, shoreline length 1689 m, maximum length 687 m, maximum width 295 m, mean width 191 m, shoreline development 1.31, maximum depth 9.45, mean depth 4.36, volume 573.8 thousands m3, mean width of littoral zone 17,4 m, catchment area (including the lake itself) 2,93 km2. Lake Tapeliai catchment is located in the moraine and limnoglacial plains of Vilija, it is characterized by a rather diverse relief, which consists of a section of Tapeliai glacial tunnel valley, limnoglacial and fliuvioglacial plains, aeolian landforms and moraine hills. Average annual precipitation is ~686 mm. Significant portion (45 %) of the annual precipitation replenishes the lake, mostly through groundwater discharge. Water residence time in the Lake Tapeliai is 0.63 years. Lake Tapeliai covers 4.5 % of the catchment area. Forests cover as much as 79.4 % of the catchment area, pine forests predominate (82.3 %). Built-up areas occupy 11.3 % of the catchment area. The predominantly sandy soils in the catchment area result in abundant groundwater inseeping, which is reflected in the springs found at the bottom of the lake. Abundant groundwater inseeping also reduces lake water level fluctuations, whose estimated amplitude from June 2018 to May 2020 reached just 21 cm. Keywords: Tapeliai Landscape Reserve, Tapeliai, Lake, Vilnius, Lithuania, bathymetric chart, morphometry.

Comparative morphosedimentary framework of small subtropical islands offshore Kuwait

Five small islands offshore of the State of Kuwait in the northern Arabian Gulf (Miskan, Awhah, Kubbar, Qaruh, and Umm Al-Maradem) occur in differing structural settings and have evolved in a dynamic environment of shifting fluvial depocenters, fluctuating Holocene sea level, and variable tidal conditions. As a first step in reconstructing the origin and evolution of the islands, bathymetric charts, historical photographs, topographic profiles, and sediment samples were used to investigate their geomorphology and sedimentary environments. The subaerial portion of the islands varies in area from 0.04 to 0.57 km2. The plan-shape ellipticity ranges from nearly circular (0.10) to oval-shaped (0.54). The northern two islands (Miskan and Awhah) experience mesotidal conditions and are situated on a shallow platform (<5 m below mean sea level), which is part of a larger Failaka Island structure. In contrast, the three southern sites have a microtidal regime and sit atop small isolated platforms of aggrading perched reef origin, which descend steeply to more than 20–30 m depth within 3 km of the islands. Topographic profiles indicate that island interiors are composed of beach-ridge sets, whereas modern shoreline consists of segments of beachrock platforms alternating with depositional salients and flying spits in areas of longshore transport convergence. The proportion of total shoreline length represented by exposed beachrock varies from 4 to 46%. Beach sediments consist of very coarse to medium sand and variable sorting, primarily due to the degree of attrition of bioclastic material. A simple conceptual model is proposed to describe the general evolutionary trajectory of end-member islands. Both their accretion during the Late Holocene sea-level stillstand and decadal-scale persistence of sediment transport convergence sites (salients) suggest a morphosedimentary stability of the islands in the near future.

Sir Anthony Seymour Laughton. 29 April 1927—27 September 2019

Anthony (Tony) Laughton was an oceanographer who promoted the science of oceanograpy in Britain. Focusing on the shape of the seafloor, his work included underwater photography, ocean drilling, long-range side-scan sonar and scientific charting of the ocean floor. Following undergraduate studies at King's College, Cambridge, he joined Maurice Hill (FRS 1962) at the Cambridge Department of Geodesy and Geophysics, beginning a career in marine geophysics. Following his PhD, he spent a year at Lamont Geological Observatory, USA, where he met many leading US workers, and became interested in deep-seafloor photography and bathymetric mapping. Returning to the UK, he joined the National Institute of Oceanography (Institute of Oceanographic Sciences from 1973) at Wormley, Surrey, and became director in 1978. He developed the first UK seafloor camera, was an enthusiastic supporter and user of the revolutionary Precision Echo Sounder and later of the GLORIA long-range side-scan sonar. He played a significant part in the International Indian Ocean Expedition, subsequently developing a new understanding of the Gulf of Aden. A consummate committee man, he had a vital role in reviving the General Bathymetric Chart of the Oceans and promoted UK involvement in the international Deep-Sea Drilling Project. He was an accomplished amateur musician (playing French horn), small-boat sailor and handyman.

The International Bathymetric Chart of the Arctic Ocean Version 4.0

Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet.

High-resolution bathymetry by deep-learning-based image superresolution.

Seafloor mapping to create bathymetric charts of the oceans is important for various applications. However, making high-resolution bathymetric charts requires measuring underwater depths at many points in sea areas, and thus, is time-consuming and costly. In this work, treating gridded bathymetric data as digital images, we employ the image-processing technique known as superresolution to enhance the resolution of bathymetric charts by estimating high-resolution images from low-resolution ones. Specifically, we use the recently-developed deep-learning methodology to automatically learn the geometric features of ocean floors and recover their details. Through an experiment using bathymetric data around Japan, we confirmed that the proposed method outperforms naive interpolation both qualitatively and quantitatively, observing an eight-dB average improvement in peak signal-to-noise ratio. Deep-learning-based bathymetric image superresolution can significantly reduce the number of sea areas or points that must be measured, thereby accelerating the detailed mapping of the seafloor and the creation of high-resolution bathymetric charts around the globe.

An early warning system for inundation forecast due to a tropical cyclone along the east coast of India

Cyclone-induced coastal inundation along the east coast of India is simulated using the state-of-the-art advanced circulation model coupled with Simulating Waves Nearshore model. Bathymetry of the computational domain is prepared by integrating digital coastal bathymetric chart with global digital elevation model (DEM) ETOPO-2. Topography of the coastal land region is created by merging data from the fine resolution airborne DEM with that from the Indian satellite CARTOSAT-2 derived CARTO2 DEM and Shuttle Radar Topography Mission DEM. The major shortcomings of coastal inundation simulation due to inaccurate representation of intricate networks of river, creeks and lagoons have been overcome by careful description of the critical coastal wetland features influencing the landward inundation of storm surge in the present work. Experimental simulation of coastal inundation is carried out for the Phailin (2013) and Hudhud (2014) cyclones. The computed surge residual for Phailin and Hudhud are compared with available tide-gauge observations, which have resulted in root mean square error of 0.06 m and 0.11 m, respectively. The simulations show realistic coastal inundations, which are compared with the Indian meteorological department records. The model set up is then used to generate forecast of coastal inundation due to Titli (2018) cyclone with a lead period of 48 h. The Weather Research and Forecasting model forecast winds at 5 km spatial resolution are used as the primary forcing parameter. The coastal inundation forecast due to Titli cyclone is validated by assessing the spatial coherency of simulated inundation with the water logged area demarcated from synthetic-aperture radar image taken from Canadian satellite RADARSAT-2. The results clearly indicate acceptability of the model performance with a potential to predict the coastal inundation during a cyclone for operational early warning.

Integrated Geodetic and Hydrographic Measurements of the Yacht Port for Nautical Charts and Dynamic Spatial Presentation

The use of geodetic and hydrographic systems, methods and measuring devices to obtain geospatial data enables integrated modeling of 3D space and related objects. Factors such as the seafloor relief of the marina and land infrastructure need to be considered to ensure safe stay of vessels in the marina. The article presents the results of bathymetric and geodetic measurements of the yacht port of the National Sailing Centre in Gdańsk. They were made with the use of several measuring methods such as a hydrographic unmanned surface vessel, GNSS positioning, enabling geodetic inventory of hydrotechnical structures and port infrastructure, as well as laser scanning that resulted in three-dimensional presentation of land objects. As a result of research and analysis, a two-dimensional bathymetric chart of the yacht port was made. Thanks to the integration of geodetic and hydrographic data, three-dimensional visualization of the marina area was obtained. The charts can be used to ensure ship navigation safety when maneuvering in port and mooring at quays.

Three-Dimensional Geomorphometric Modeling of the Arctic Ocean Submarine Topography: A Low-Resolution Desktop Application

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.

Web-Based Sea Level Change Simulation System Using PNG Elevation Tiles and Smart Tile Architecture

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.

Sedimentary Inputs and Morphology Characterization of the Bottom Agropastoral Lake of Nafoun (North Ivory Coast)

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.

Assessment of the Malaysian Tidal Stream Energy Resources

As a developing country, Malaysia has shown great interest and effort to commit and invest for green technology and green energy especially tidal energy resources. This research project is conducted to carry out an assessment study to analyse and compare several locations in Malaysia while using the optimal analytical approach in finding the best sites to harness tidal stream resource around Malaysia. Previous studies that only considered flow velocity at the deployment sites may not be accurate since geometry of the coastal region and the friction force exerted from the tidal flow with the seabed can also contribute to the suitability of the proposed tidal sites. Tidal Model Driver was used to extract tidal elevation data on specific harmonic constituents and tidal velocity attribute, and then compared to the data obtained from General Bathymetric Chart of the Oceans. The weighted decision matrix was used to analyse the potential of each location by considering essential criteria such as tidal velocity, depth of coastline, geometry of coastline and environmental impacts. Top locations with the highest score were chosen as potential location to invest in a tidal energy farm, which consists of Pulau Pangkor, Port Dickson, and Pulau Tioman among others. The locations that produce the highest yearly energy density are found to be Pulau Pangkor with 1.21 MWh/year followed by Pulau Pinang with 836.5 kWh/year. Notably, the inclusion of other factors besides tidal velocity such as the site characteristic and the amount of potential impact to the environment provided different outcome than published materials in this field.