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Bathymetric surveys of Juodis and Lydekinis Lakes (located in outskirts of Vilnius city, Lithuania) were carried out on April 28 and May 1, 2020, from a boat with attached Lowrance HDI SKIMMER XDCR transducer (200 kHz), Simrad GO5 chartplotter and Lowrance Point-1 GPS/Glonass receiver. 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 (0.5x0.5 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. Juodis and Lydekinis are small shallow lakes of glaciokarst origin, located in Tapeliai glacial tunnel valley. Juodis Lake is considerably elongated while shape of Lydekinis Lake is close to the circle. According to survey data, the surface area of Juodis Lake is 9.2 ha, water surface elevation 135.8 m a.s.l., maximum depth 3.7 m, mean depth 1.2 m, volume 114.9 thousands m3, catchment area 344 ha. The surface area of Lydekinis Lake is 1.7 ha, water surface elevation 138.2 m a.s.l., maximum depth 4.9 m, mean depth 2.2 m, volume 36.3 thousands m3, catchment area 71 ha. During the observation period (from June of 2018 to April of 2022), the annual amplitude of water level fluctuations in Juodis Lake reached up to 0.16 m. Water level fluctuations in Lydekinis lake were very large due to the reconstruction of the dam and the installation of new culverts. Currently, the water level in Lydekinis Lake is significantly raised, most of the lake shore and the surrounding wetland are flooded. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 physical-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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]